Cambridge International AS & A Level Biology 9700 · 2016. 2. 16. · Cambridge International AS &...

Scheme of Work

Cambridge International AS & A Level

Biology

9700 For examination from 2016

Contents

Introduction ................................................................................................................................................................................................................................................ 3

Unit 1: Biological molecules .................................................................................................................................................................................................................... 11

Unit 2: Cells as the basic units of life ...................................................................................................................................................................................................... 28

Unit 3: DNA and the mitotic cell cycle ..................................................................................................................................................................................................... 42

Unit 4: Transport and gas exchange ....................................................................................................................................................................................................... 51

Unit 5: Disease and protection against disease ...................................................................................................................................................................................... 71

Unit 6: The diversity of life ....................................................................................................................................................................................................................... 86

Unit 7: Genetics, population genetics and evolutionary processes ....................................................................................................................................................... 100

Unit 8: Molecular biology and gene technology .................................................................................................................................................................................... 121

Unit 9: Respiration ................................................................................................................................................................................................................................. 140

Unit 10: Mammalian physiology, control and coordination .................................................................................................................................................................... 152

Unit 11: Plant physiology and biochemistry .......................................................................................................................................................................................... 170

Cambridge International AS & A Level Biology (9700) – from 2016 Scheme of Work

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Introduction

This staged teaching scheme of work provides ideas about how to construct and deliver a two-year course of study with all of the AS Level syllabus taught in Year 1 and the remainder of the A Level syllabus taught in Year 2. The syllabus has been broken down into teaching units, which incorporate one or more of the syllabus units, with suggested teaching activities and learning resources to use in the classroom. Recommended prior knowledge

Learners should have attained at least a grade C in IGCSE or O Level Biology, or the equivalent in another award such as Co-ordinated Science. Outline

Whole class (W), group work (G), pair (P) and individual activities (I) are indicated, where appropriate, within this scheme of work. Suggestions for homework (H) and formative assessment (F) are also included. The activities in the scheme of work are only suggestions and there are many other useful activities to be found in the materials referred to in the learning resource list. Opportunities for differentiation are indicated as basic and challenging; there is the potential for differentiation by resource, length, grouping, expected level of outcome, and degree of support by the teacher, throughout the scheme of work. Length of time allocated to a task is another possible area for differentiation. Where a learning objectives has been divided so that part of that learning objective content is taught at a different time to the rest of the learning objective, these are identified by (i) or (ii), etc., and the specific part of the learning objective is in bold. Key concepts

The key concepts on which the syllabus is built are set out below. These key concepts can help teachers think about how to approach each topic in order to encourage learners to make links between topics and develop a deep overall understanding of the subject. As a teacher, you will refer to these concepts again and again to help unify the subject and make sense of it. If mastered, learners can use the concepts to solve problems or to understand unfamiliar subject-related material.

Cells as the units of life A cell is the basic unit of life and all organisms are composed of one or more cells. There are two fundamental types of cell: prokaryotic and eukaryotic.

Biochemical processes Cells are dynamic: biochemistry and molecular biology help to explain how and why cells function as they do.

DNA, the molecule of heredity Cells contain the molecule of heredity, DNA. Heredity is based on the inheritance of genes.

Natural selection Natural selection is the major mechanism to explain the theory of evolution.

Organisms in their environment


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All organisms interact with their biotic and abiotic environment.

Observation and experiment The different fields of biology are intertwined and cannot be studied in isolation: observation and enquiry, experimentation and fieldwork are fundamental to biology.

Some of the ideas in this syllabus can take time to be fully understood. By linking them together through the key concepts, learners will have more opportunity for those ideas to make sense to them and how they connect to other areas of the syllabus. The key concepts themselves will not be directly assessed; rather they are themes that learners will be able to use to order their thoughts, themes and knowledge to express answers in examinations and interviews for work or the next stage of their study.

As learners progress through the course, it is important that they do not regard the different topics as being totally self-contained and unconnected, studied in complete isolation from one another. By keeping the key concepts to the fore at all stages of your teaching, you can strongly encourage learners to regard the subject as a set of interconnected themes. Learners should be aware that an ability to see how different strands of the syllabus can be pulled together within one key concept is a high-level transferable skill. Linking different areas of their knowledge through a common thread of ideas, or ways of understanding and explaining, is enhancing their higher-order thinking skills. These skills are the building blocks of deeper and broader learning, those that universities look for in their students and which allow learners to answer examination questions fully and with links from more than one part of the syllabus. Teachers can introduce key concepts as an integral part of their teaching approach and consolidate them when appropriate. This will help their learners to appreciate that some themes and theories are revisited and built upon during the course and that, by bringing together very different areas of the syllabus, these themes are fundamental to our understanding of the subject. Focussing on these concepts will improve learners’ self-confidence in their ability to progress, as well as enabling them to revise more effectively; learners could make mind maps across the syllabus on each of the key concepts as a way of revising. By visualising the subject as being formulated from these basic ideas, they will become better prepared for interviews and future study at university, or be more adaptable to themes currently under research and development in industrial and academic institutions. There is also merit in showing learners how, during the course, they will be biologists studying in a number of inter-related fields that can be drawn together by the key concepts. Examples of these fields - cell biology, biochemistry, physiology, genetics, evolutionary biology, microbiology, epidemiology, immunology, biotechnology, ecology, population biology and conservation biology - can be discussed and linked to the different areas of the syllabus. The key concepts are listed under the relevant learning objectives, those in bold are where the coverage of the learning objective makes a significant contribution to the key concept.


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Practical work

Practical work is an essential part of science. Scientists use evidence gained from prior observations and experiments to build models and theories. Their predictions are tested with practical work to check that they are consistent with the behaviour of the real world. Learners who are well trained and experienced in practical skills will be more confident in their own abilities. The skills developed through practical work provide a good foundation for those wishing to pursue science further, as well as for those entering employment or a non-science career.

Twelve Practical Booklets have been developed for this syllabus, six for Paper 3 and six for Paper 5, and are available on Teacher Support at http://teachers.cie.org.uk and are referenced within this scheme of work.

The Teaching A Level Science Practical Skills booklet is also available on Teacher Support at http://teachers.cie.org.uk which contains useful information and suggestions for teaching A Level practical skills. Suggested teaching order

The learning objectives and activities in this scheme of work are arranged in a suggested teaching order rather than the order that they appear in the syllabus. It has been written for the staged route, with Units 1 to 5 covering the learning objectives to be studied by all learners in the first year, and which can be assessed by the AS Level qualification. This is followed by Units 6 to 11 which cover all learning objectives that will be assessed by the full A Level qualification at the end of the second year of the course.

For classes taking the linear route, where all learners take the full A Level, this allows for the integrated teaching of AS and A Level learning objectives across both years of the A Level course. The linear route is not covered in this scheme of work. The units within this scheme of work are:

Suggested time allocation (%)

AS Level A Level

Unit 1. Biological molecules

10

Water 2.3.d

Carbohydrates 2.2.b, 2.2.a, 2.2.c, 2.1.a(i), 2.1.b, 2.2.d, 2.2.e

Lipids 2.2.f, 2.2.g, 2.1.a(ii)

Proteins 2.1.a(iii), 2.3.a, 2.3.b, 2.3.c

Biochemical tests 2.1.a

Nucleic acids 6.1.a, 6.1.b

Enzymes 3.1.a, 3.1.b, 3.1.c, 3.1.d, 3.2.a, 3.2.b, 3.2.c, 3.2.d

Unit 2. Cells as the basic units of life

9 Cells and microscopy 1.1.d, 1.1.a, 1.1.c

Size and magnification calculations 1.1.b, 1.1.e

Plant and animal cells 1.2.b, 1.2.c, 1.2.a

http://teachers.cie.org.uk/



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Bacteria 1.2.d

Prokaryotic versus eukaryotic cell structure 1.2.e

Viruses 1.2.f

Cell membrane structure and function 4.1.a, 4.1.b, 4.1.c

Transport across membranes 4.2.a(v), 4.2.c, 4.2.a(i), 4.2.d, 4.2.b, 4.2.a(ii), 4.2.a(iii), 4.2.f, 4.2.e, 4.2.a(iv)

Unit 3. DNA and the mitotic cell cycle

7

Chromosome structure 5.1.a

The mitotic cell cycle - overview 5.1.c

The mitotic cell cycle – DNA replication 6.1.c, 5.1.d

The mitotic cell cycle – mitosis and cytokinesis 5.1.b, 5.1.e, 5.2.a, 5.2.b

Protein synthesis, introduction to genes and mutation 6.2.a, 6.2.b, 6.2.c, 6.2.d

Unit 4. Transport and gas exchange

14

Plant anatomy and histology 7.1.a, 7.1.b, 7.1.c

Transport of water and mineral ions 7.2.a, 7.2.c, 7.2.b, 7.2.d, 7.2.e, 7.2.f

Transport of assimilates 7.2.g, 7.2.h, 7.2.i

Structure to function: plants 7.1.d

The mammalian circulatory system 8.1.a, 8.1.b, 8.1.c, 8.1.d, 8.1.e

The mammalian heart 8.2.a, 8.2.b, 8.2.c, 8.2.d

The human gas exchange system 9.1.a, 9.1.b, 9.1.c, 9.1.d

Carriage of respiratory gases 8.1.f, 8.1.g, 8.1.h

Unit 5. Disease and protection against disease

10

Disease and smoking 10.1.a, 9.2.a, 9.2.b

Infectious disease 10.1.b, 10.1.c, 10.1.d, 10.1.e

Antibiotics 10.2.a, 10.2.b, 10.2.c

The immune response 11.1.d, 11.1.a, 11.1.b, 11.1.e, 11.1.c, 11.1.f

Antibodies 11.2.a, 11.2.b, 11.2.c

Vaccination 11.2.d, 11.2.e

Unit 6. The diversity of life

6 Definitions 18.1.a

Classification 18.2.a, 18.2.b, 18.2.c, 18.2.d


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Biodiversity 18.1.b

Fieldwork 18.1.c, 18.1.d, 18.1.e, 18.1.f

Conservation, population control and maintaining biodiversity

18.3.a, 17.3.e, 18.3.b, 18.3.g, 18.3.c, 18.3.d, 18.3.e, 18.3.f, 18.3.h

Unit 7. Genetics, population genetics and evolutionary processes

10

Understanding terms 16.1.a, 16.1.b, 16.2.a(i)

Meiotic cell division and heredity 16.1.c, 16.1.d, 16.1.e

Genetic crosses 16.2.a(ii), 16.2.b, 16.2.c, 16.2.d

Biological variation 17.1.a, 17.1.c, 17.1.b, 16.2.e, 16.2.f, 16.2.g

Natural selection and population genetics 17.1.d, 17.2.a, 17.2.b, 17.2.c, 17.2.d

Evolution and speciation 17.3.a, 17.3.b, 17.3.c, 17.3.d

Artificial selection 17.2.e, 17.2.f

Unit 8. Molecular biology and gene technology

9

The control of gene expression 16.3.b, 16.3.a, 16.3.c, 19.1.i

Recombinant DNA technology 19.1.a, 19.1.b, 19.1.h, 19.1.e, 19.1.f, 19.1.g, 19.2.c, 19.3.a, 19.3.b, 19.3.c

Molecular biology techniques 19.1.c, 19.1.d, 19.2.g

Bioinformatics 19.2.a, 19.2.b

Prevention and treatment of inherited conditions. 19.2.d, 19.2.e, 19.2.f

Unit 9. Respiration

7

Energy and ATP 12.1.a, 12.1.b

Aerobic respiration and ATP synthesis 12.2.a, 12.2.b, 12.2.c, 12.2.d, 12.2.e, 12.1.c, 12.2.g, 12.2.f, 12.1.e(i), 12.1.d, 12.2.i

Anaerobic respiration 12.2.k, 12.2.l

Comparing anaerobic and aerobic respiration 12.2.j

Yeast practical 12.2.h

Respiratory substrates, RQs and respirometers 12.1.f, 12.1.g, 12.2.m, 12.1.h

Unit 10. Mammalian physiology, control and coordination

10

Communication systems 15.1.a

The nervous system 15.1.b, 15.1.c, 15.1.d, 15.1.e, 15.1.f, 15.1.g, 15.1.h

Muscle contraction 15.1.i, 15.1.j, 15.1.k

Homeostasis 14.1.a, 14.1.b, 14.1.c


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Excretion of nitrogenous waste and osmoregulation 14.1.d, 14.1.e, 14.1.f, 14.1.g

Control of blood glucose concentration 14.1.h, 14.1.i, 14.1.j

Detection of biological molecules in blood and urine 14.1.k, 14.1.l

Hormones of the menstrual cycle 15.1.l, 15.1.m

Unit 11. Plant physiology and biochemistry

8

Photosynthesis overview 13.1.b

The light dependent stage 13.1.c, 13.1.d, 13.1.e, 13.1.f

The light dependent stage - chemiosmosis 12.1.e(ii)

The light independent stage 13.1.a, 13.1.g, 13.1.h

The chloroplast 13.3.a

Factors affecting photosynthesis. 13.2.a, 13.2.b, 13.2.c, 13.2.d, 13.2.e, 13.3.b

Control and coordination in plants. 15.2.a, 14.2.a, 14.2.b, 14.2.c, 15.2.b, 15.2.c, 15.2.d, 16.3.d

Suggested teaching order

AS Level Unit 1, Biological molecules, could be studied either before or after Unit 2, Cells as the basic units of life. Learners with a good chemistry background will cope well with Unit 1, others will probably find the subject matter in Unit 2 to be more approachable. If Unit 2 is covered first, then learners will need a reminder of previous knowledge of biological molecules learned in earlier studies or a brief introduction to lipids and proteins. Knowledge and understanding from both of these will be used and applied in the rest of the course. The role of DNA in the mitotic cell cycle, Unit 3, follows on quite logically from the work done in Units 1 and 2. Unit 5, Disease and protection against disease is best taught after Unit 4, Transport and gas exchange, as there is a link between mammalian transport and gas exchange in mammals in Unit 4 and non-infectious disease and cells of the immune system in Unit 5. There is much work that can be done in improving data extraction and data analysis skills in Unit 5, where there are fewer opportunities to carry out practical work. As this unit is taught at the end of the AS Level course, teachers may wish to allocate some time to consolidate practical skills gained earlier in the course and prepare learners fully for Paper 3. A Level Having studied eukaryotic and prokaryotic cell structure in Unit 2 (AS Level), Unit 6, The diversity of life, is a straightforward introduction to the A Level syllabus. This covers knowledge and understanding that is useful for Unit 7, Genetics, population genetics and evolutionary processes. Unit 8, Molecular biology and gene technology, allows learners to use some of the concepts covered in Unit 7. Unit 11 can be taught at any time throughout the course if carrying out practical work is dependent on seasonal timing: if taught before Units 9 and 10, the idea of control and coordination and chemiosmosis should be covered. Units 9 and 11 are best taught with a gap in between to avoid confusion for learners when studying the biochemical processes of respiration and photosynthesis. Teacher support

Teacher Support (http://teachers.cie.org.uk) is a secure online resource bank and community forum for Cambridge teachers, where you can download specimen and past question papers, mark schemes and other resources. We also offer online and face-to-face training; details of forthcoming training opportunities are posted online.



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This scheme of work is available as PDF and an editable version in Microsoft Word format; both are available on Teacher Support at http://teachers.cie.org.uk. If you are unable to use Microsoft Word you can download Open Office free of charge from www.openoffice.org. Resources

The resources for this syllabus, including textbooks endorsed by Cambridge, can be found at www.cie.org.uk and Teacher Support http://teachers.cie.org.uk. Endorsed textbooks have been written to be closely aligned to the syllabus they support, and have been through a detailed quality assurance process. As such, all textbooks endorsed by Cambridge for this syllabus are the ideal resource to be used alongside this scheme of work as they cover each learning objective.

Where other textbooks have shown to be useful for some learning objectives they are referred to by the first author. These include:

King T, Reiss M, Roberts M. Practical Advanced Biology. Nelson Thornes, 2nd

Edition 2001. ISBN: 9780174483083

Siddiqui S. Comprehensive Practical Biology for A Level. Ferozsons, 1999. ISBN 9690015729

Bio Factsheets. Curriculum Press www.curriculum-press.co.uk These cover a wide range of topics and are also useful for revision and extension work. Individual factsheets can be obtained, as can a complete CD-ROM.

Biological Nomenclature, published by the Society of Biology (formerly the Institute of Biology). This publication can be ordered by emailing the Education Department at the Society of Biology https://www.societyofbiology.org. The symbols, signs and abbreviations used in examination papers follow these recommendations. CD-ROM Bioscope. Cambridge University Press. ISBN: 9781845650261 A simulation of a real microscope that includes a large number of botanical and zoological microscope slides at a range of magnifications, accompanied by paper-based tasks. It can be used for whole class teaching via a whiteboard or data projector, or by individual students on PCs. Websites This scheme of work includes website links providing direct access to internet resources. Cambridge International Examinations is not responsible for the accuracy or content of information contained in these sites. The inclusion of a link to an external website should not be understood to be an endorsement of that website or the site's owners (or their products/services).

The particular website pages in the learning resource column of this scheme of work were selected when the scheme of work was produced. Other aspects of the sites were not checked and only the particular resources are recommended. Websites in this scheme of work, and some other useful websites, include:

http://www.ncbe.reading.ac.uk/ The National Centre for Biotechnology Education: protocols and useful information

http://www.saps.org.uk/ Science and Plants for Schools: protocols

http://www.biology4all.com/resources_library/index.asp Biology 4all: wide range of resources and links to other useful sites


http://www.openoffice.org/

http://www.cie.org.uk/


http://www.curriculum-press.co.uk/

https://www.societyofbiology.org/

http://www.ncbe.reading.ac.uk/

http://www.saps.org.uk/

http://www.biology4all.com/resources_library/index.asp


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http://www.s-cool.co.uk/alevel/biology.html S-cool: revision website

http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookTOC.html The Online Biology Book, hosted by Estrella Mountain Community College

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/ Kimball’s Biology Pages (especially useful for teacher reference)

http://www.cellsalive.com/ Cells Alive: covers a range of topics with straightforward animations

http://www.worldofteaching.com/A-ZBiologypowerpoints.html PowerPoint presentations donated by teachers

http://www.ase.org.uk/resources/ Association for Science Education: educational resources

http://www.nuffieldfoundation.org/practical-biology Practical Biology: ideas and lesson plans

http://www.nationalstemcentre.org.uk/sciencepracticals The National Stem Centre provides many resources including ideas for practical work

http://www.biology-resources.com For learners to revisit IGCSE topics

http://www.biologyjunction.com/ap_biology_animations.htm Links to websites with animations - many different topics

http://www.rsc.org/Education/Teachers/Resources/cfb/index.htm Royal Society of chemistry: Chemistry for biologists

https://www.societyofbiology.org/ The Society of biology

http://www.s-cool.co.uk/alevel/biology.html

http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookTOC.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/

http://www.cellsalive.com/

http://www.worldofteaching.com/A-ZBiologypowerpoints.html

http://www.ase.org.uk/resources/

http://www.nuffieldfoundation.org/practical-biology

http://www.nationalstemcentre.org.uk/sciencepracticals

http://www.biology-resources.com/

http://www.biologyjunction.com/ap_biology_animations.htm

http://www.rsc.org/Education/Teachers/Resources/cfb/index.htm

https://www.societyofbiology.org/


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Unit 1: Biological molecules

Recommended prior knowledge

Learners will need some background knowledge in chemistry before embarking on this unit. They should understand the terms atom, molecule, electron and ion. They should also have a basic understanding of covalent and ionic bonding, and of molecular and structural formulae. They should be able to write and understand simple chemical equations. Some knowledge of energy changes (potential energy and bond energy) would be helpful. http://www.rsc.org/Education/Teachers/Resources/cfb/basicchemistry.htm is a good starting point for learners to revise their knowledge of chemistry. http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page1.html this also covers basic chemistry for biologists. Context

This unit provides essential reference material for learners when studying all future units in their Cambridge International AS and A Level course. Knowledge of how the structure and properties of biological molecules are related to their functions in cells and in organisms is fundamental to an understanding of many areas of biology. The molecule of heredity, DNA, is a key concept. Cells can be visualised as structural units requiring biological molecules and as dynamic units carrying out biochemical processes. Cells carry out biochemical processes, a key concept, and enzymes catalyse biological reactions. A thorough understanding of enzyme function can be applied to studying processes such as:

DNA replication and protein synthesis in Unit 3, The role of DNA in the mitotic cell cycle;

the carriage of carbon dioxide in Unit 4, Transport and gas exchange;

gene technology in Unit 8, Molecular biology and gene technology;

respiration in Unit 9, Respiration;

photosynthesis in Unit 11, Plant physiology and biochemistry. As part of biotechnology, enzymes are used commercially in a range of applications, with many of these using immobilised enzymes for a more efficient process. Outline

This unit introduces learners to the biological molecules that are required by cells for both structural purposes and physiological processes. The main groups of organic biochemicals, carbohydrates, lipids, proteins and nucleic acids, are studied. For carbohydrates, lipids and proteins, there is an emphasis on the relationship between molecular structure, properties and functions in living organisms. Learners study the structure of nucleic acids and discuss DNA as the ideal molecule of inheritance in preparation for Unit 3, The role of DNA in the mitotic cell cycle. Learning objective 2.3.d introduces the concepts of hydrogen bonding and solubility and considers the roles of water in living organisms. This unit builds on knowledge of protein structure in describing and explaining enzyme activity. The mode of action of enzymes and factors that affect enzyme action, including inhibitors, is covered. Learners are introduced to some basic enzyme kinetics. There are many opportunities to carry out practical work, where learning can be reinforced and individual and class results can be analysed. The last section of the unit considers the differences between enzymes free in solution and immobilised enzymes. Teaching time

It is recommended that this unit should take approximately 10% of the complete A Level course.

http://www.rsc.org/Education/Teachers/Resources/cfb/basicchemistry.htm

http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page1.html


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Learning objectives Suggested teaching activities Learning resources

2.3.d explain how hydrogen bonding occurs between water molecules and relate the properties of water to its roles in living organisms (limited to solvent action, specific heat capacity and latent heat of vapourisation) Key concepts Cells as the units of life, Biochemical processes, Organisms in their environment

Discussion / brainstorm: the importance of water to the life of a cell, including hydrogen bonding and as a solvent in biological systems (e.g. blood, phloem sap, cytosol/cytoplasm). (I) (Basic).

Learners make notes, including the following: o Draw and describe hydrogen bonding between water molecules. (I)

(Basic) o Make links between hydrogen bonding and the cohesive nature of water

molecules. (I) (Basic) o Explain the link between hydrogen bonding and

the high specific heat capacity of water the high latent heat of vapourisation of water. (I) (Challenging)

o Research examples to show the relationship between the properties of water and its roles in organisms. (I) (Challenging)

Discuss the concept of polar / non-polar and the solubility or otherwise of the biological molecules in this unit. (W) (Basic)

Note

Ensure learners can use the following terms (see Unit 2):

hydrophilic hydrophobic

polar non-polar

charged / ionic uncharged / non-ionic

water soluble water-insoluble

lipid insoluble lipid soluble

Online http://faculty.fmcc.edu/mcdarby/major

s101book/chapter_03-chemistry/03-Water_Properties.htm

http://www.rsc.org/Education/Teachers/Resources/cfb/water.htm

http://www.worldofmolecules.com/solvents/water.htm

Textbooks/Publications Bio Factsheet 30: The biological

importance of water. Bio Factsheet 78: Chemical bonding

in biological molecules

2.2.b define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide Key concepts Biochemical processes, DNA, the molecule of heredity

Learners write definitions for macromolecule, monomer and polymer and consolidate. (W) (Basic) o Match the terms with relevant examples (include an introduction of DNA

and RNA nucleotides). o Discuss why lipids do not have monomers. o Construct a simple table (complete bond names later).

type of organic macromolecule

monomer polymer name of bond

carbohydrate monosaccharide polysaccharide

protein amino acid polypeptide

nucleic acid DNA nucleotide RNA nucleotide

polynucleotide

lipid - -

Online http://www.rsc.org/Education/Teache

rs/Resources/cfb/carbohydrates.htm Textbooks/Publications Bio Factsheet 78: Chemical bonding


http://faculty.fmcc.edu/mcdarby/majors101book/chapter_03-chemistry/03-Water_Properties.htm







http://www.rsc.org/Education/Teachers/Resources/cfb/carbohydrates.htm

http://www.rsc.org/Education/Teachers/Resources/cfb/carbohydrates.htm


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Further discussion (W) (Basic) o The macromolecules are based on a skeleton of carbon atoms (‘life is

based on carbon'), which can form strong bonds with other atoms. o Of the wide range of organic compounds formed, some provide energy for

the cell.

Introduce the terms condensation and hydrolysis by discussing the synthesis and breakdown of polymers. (W) (Basic)

Brainstorm some carbohydrates and agree whether monosaccharide, disaccharide or polysaccharide (W) (Basic) o Learners make notes on: monosaccharides, using the terms triose,

pentose and hexose (glucose, galactose and fructose as e.g. of hexoses); disaccharides (lactose, maltose, sucrose and cellobiose), giving their constituent monosaccharides). (I) (Basic)

Note

Useful terms for later: o pentose - nucleotide and nucleic acid structure in this unit, o hexose for respiration (Unit 9 ) and photosynthesis (Unit 11).

2.2.a

describe the ring forms of -glucose

and glucose Key concepts Biochemical processes

Provide details of the molecular structure of glucose (see 2.2.b) which, in solution, is mainly in ring form (W) (Basic) o Show learners how to use a logical sequence to build up the ring form of

the glucose molecule and number the carbon atoms. Learners practise then draw the molecule from memory. (I) (Challenging)

o Learners complete a range of incomplete diagrams prepared by you, e.g. by adding the -OH and -H groups. (F)

o Progress learners to be able to identify and draw a glucose molecule. (I) (Basic)

Learners make molecular models of and forms of glucose using plastic sphere / bond models or drinking straw models. (P) (Challenging)

Explain that knowledge of the and forms of glucose will help understanding of disaccharide and polysaccharide structures and properties. (W) (Basic)


rs/Resources/cfb/carbohydrates.htm#2

Past Papers Paper 22, Nov 2011, Q4 (a)

2.2.c describe the formation of a glycosidic bond by condensation, with reference

Outline how a glycosidic bond is formed to produce a disaccharide by a condensation reaction (no details yet of molecular structure). (W) (Basic)

Learners draw the formation of an , 1-4 glycosidic bond and add the name of

Past Papers Paper 22, Nov 2011, Q4 (b)

http://www.rsc.org/Education/Teachers/Resources/cfb/carbohydrates.htm#2




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both to polysaccharides and to disaccharides, including sucrose Key concepts Biochemical processes

the bond to their table from 2.2.b. (I) (Challenging)

Work through the formation of a , 1-4 glycosidic bond (to form cellobiose). (W) (Challenging)

Tell learners that the glucose monomer of sucrose is -glucose and ask them to use a molecular diagram of a sucrose molecule to work out the structure of a fructose molecule (no need to memorise this). (W) (Challenging)

Learners use the -glucose models previously constructed to form a glycosidic bond. (P) (I) (Basic) o Produce a section of a polysaccharide, e.g. from an amylose or cellulose

molecule. (G) (P) (I) (Challenging)

Note

Maltose is formed in nature from degradation reactions (i.e. breakdown) of starch, so focus the activity on the concept of a condensation reaction to build up a macromolecule and the formation of a glycosidic bond. The ‘formation’ of maltose illustrates the principle of glycosidic bond formation by a condensation reaction.

Textbooks/Publications Bio Factsheet 78: Chemical bonding


2.1.a (i) carry out tests for reducing sugars and non-reducing sugars, the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins to identify the contents of solutions Key concepts Biochemical processes, Observation and experiment

Only the first part of this learning objective is included here: carry out tests for reducing sugars and non-reducing sugars, and the iodine in potassium iodide solution test for starch to identify the contents of solutions

Discuss the tests and explain they are useful to identify biochemicals in a range of plant and animal material. (W) (Basic) o Learners should describe the biochemical tests (‘food tests’ is a less

helpful term) and the results obtained, giving conclusions. (W) (Basic)

Practical work: carrying out the Benedict's test for reducing sugars. o Explain that a negative test does not mean an absence of carbohydrate.

(I) (Basic) o Learners test substances that will give positive results (e.g.

glucose/fructose/ maltose/lactose solution) and negative results (e.g. sucrose solution, water, protein/starch suspension, vegetable oil). (I) (Basic)

o Learners test natural liquefied biological materials (e.g. fruits, tubers) and liquefied foods from the diet. (I) (Basic) (Challenging)

o Learners test a thin section of fruit placed on a microscope slide (add a few drops of Benedict’s and heat over a spirit burner – use forceps): use a microscope to observe colour changes. (P) (I) (Challenging)

Practical booklet 2 Online http://www.mrothery.co.uk/bio_web_

prac/practicals/2Food%20Tests.doc http://www.mrothery.co.uk/module1/

Mod%201%20techniques.htm http://www.biotopics.co.uk/nutrition/fo

otes.html Textbooks/Publications King p.19-22 Siddiqui p.56-60 Bio Factsheet 173: How to identify

foods: Food Tests and Chromatography

http://www.mrothery.co.uk/bio_web_prac/practicals/2Food%20Tests.doc


http://www.mrothery.co.uk/module1/Mod%201%20techniques.htm


http://www.biotopics.co.uk/nutrition/footes.html



V3.1 15


Discuss the negative result for reducing sugar with sucrose and explain that hot acid is used to hydrolyse sucrose, but neutralisation is required before adding Benedict’s. (W) (Basic)

Practical work carrying out the test for a non-reducing sugar, where learners use fresh samples of each of the substances that gave ‘negative’ results for the reducing sugar test. (I) (Basic)

Practical work to consolidate reducing sugars and non-reducing sugar tests. o Learners identify which unmarked solution is: glucose; sucrose; a mixture

of both glucose and sucrose. (I) (Basic) o Extend this (excess of Benedict’s solution) to filtering the precipitates for

comparison and using a colorimeter (if available) to compare filtrates. (P) (I) (Challenging)

Practical work to test for starch in a range of different types of starch (suspensions) and food substances using iodine in potassium iodide solution. Learners see a range of blue-black colours obtained (owing to the differing proportions of amylose to amylopectin). (I) (Basic)

Practical booklet 2 can be carried out after this stage. See the Teacher’s practical notes regarding the development of certain skills for Paper 3.

Note

Remind learners to control variables.

AR (analytical reagent) sucrose is preferred to LR (laboratory reagent) sucrose (preferred to cane sugar) for the non-reducing sugar test (if cane sugar is used, explain that it will contain impurities and may give a slight positive Benedict’s test results).

2.1.b carry out a semi-quantitative Benedict’s test on a reducing sugar using dilution, standardising the test and using the results (colour standards or time to first colour change) to estimate the concentration Key concepts Biochemical processes, Observation and experiment

Practical work: learners practise, and get a visual impression of, diluting a coloured liquid, using water, to set concentrations. (I) (Basic)

Practical work: learners prepare glucose solutions of known concentration and then carry out the Benedict's test, recording the time taken for the first indication of colour change and to obtain colour standards. (I) (Basic) o Follow-up with a semi-quantitative analysis, comparing time taken and

colour/colour depth to determine the approximate concentration of an unknown solution. (I) (Challenging)

o Evaluate the test with learners and ask for ideas of other semi-quantitative tests (e.g. allow precipitate to settle, dry and weigh). (W) (Challenging)

Practical booklet 2 can be carried out after this stage. See the Teacher’s

Practical booklet 2


V3.1 16


practical notes regarding the development of certain skills for Paper 3.

2.2.d describe the breakage of glycosidic bonds in polysaccharides and disaccharides by hydrolysis, with reference to the non-reducing sugar test Key concepts Biochemical processes, Observation and experiment

Explain how a glycosidic bond can be broken by hydrolysis, referring to monomers and monosaccharides. (W) (Basic)

Learners draw diagrams of the breakage of glycosidic bonds (by hydrolysis) of maltose and sucrose. (I) (Challenging) o Add annotations to explain the ideas behind the non-reducing sugar test.

(I) (Basic) o Use the models of disaccharides previously constructed to demonstrate

the breakage of a glycosidic bond. (P) (I) (Basic) o Extension activity: using molecular diagrams of galactose, lactose and

cellobiose, learners draw diagrams or construct models to show the breakdown of lactose and cellobiose. (P) (I) (Challenging)

Note

Learners should describe the breakage of the glycosidic bond in sucrose when explaining non-reducing sugar test results (see 2.1.a)


rs/Resources/cfb/carbohydrates.htm#2

2.2.e describe the molecular structure of polysaccharides including starch (amylose and amylopectin), glycogen and cellulose and relate these structures to their functions in living organisms Key concepts Cells as the units of life, Biochemical processes

Use the molecular models to show short sections of amylose and amylopectin (or strings of beads on wire) and discuss glycogen structure. (G) (Basic)

Learners describe the difference between the structures (include bonds formed) and highlight the idea of ‘structure to function ‘. o More compact structures for storage linked to the coiling effect (amylose)

and branching (amylopectin). o Branching of amylopectin and glycogen provides large number of ‘ends’ to

attach /detach glucose units. (I) (Basic)

Demonstrate (molecular model / animation) how a straight chain is produced

when forming polysaccharides with alternate -glucose residues that rotate by 180°.(W) (Basic)

Emphasise the structure to function of cellulose is different to that of the cell wall. (W) (Basic)

Discuss the role of cellulose, then learners produce explanatory notes with diagrams of how straight parallel chains are useful for structural purposes and how hydrogen bonding (2.3.d) allows parallel cellulose molecules to form fibrils (links to cell wall structure in Unit 2). (I) (Challenging)

Learners complete a gap-filling worksheet prepared by you to serve as a summary of the main learning points for carbohydrates. (F)

Online http://www.rpi.edu/dept/bcbp/molbioc

hem/MBWeb/mb1/part2/sugar.htm http://www.calfnotes.com/pdffiles/CN

102.pdf Textbooks/Publications Bio Factsheet 39: Carbohydrates:

revision summary Bio Factsheet 174: The structure and

function of polysaccharides Past Papers Paper 21, June 2011, Q5 Paper 22, Nov 2012, Q1 (d)




http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/sugar.htm

http://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/sugar.htm

http://www.calfnotes.com/pdffiles/CN102.pdf

http://www.calfnotes.com/pdffiles/CN102.pdf


V3.1 17


2.2.f describe the molecular structure of a triglyceride with reference to the formation of ester bonds and relate the structure of triglycerides to their functions in living organisms Key concepts Cells as the units of life, Biochemical processes

Draw the general formula for a fatty acid. o Explain that it is a carboxylic acid and outline -COOH as the carboxyl

group. o Explain R is a hydrocarbon chain, and extend this to explain saturated or

unsaturated fatty acids. (W) (Basic)

Draw the molecular structure of glycerol and state that a triglyceride is produced with the attachment of three fatty acids in condensation reactions. (W) (Basic) o With prompting, learners work out how ester bonds form and add the

name of the bond to their table of 2.2.b. (I) (Challenging)

Learners make simple paper cut-out models of triglycerides to illustrate the absence of polar groups and show the non-polar exposed fatty acids (so not soluble when in contact with watery liquids). (W) (Basic)

Learners describe evidence that makes triglycerides good energy stores (many C-C bonds; highly reduced so energy can be released by oxidation; insoluble in water so can be localised in the organism). (G) (P) (I) (Challenging)

Online http://www.biotopics.co.uk/as/lipidcon

densation.html http://www.chemguide.co.uk/organicp

rops/esters/background.html Textbooks/Publications Bio Factsheet 42: The structure and

function of lipids. Bio Factsheet 74: The structure and

biological functions of lipids. Bio Factsheet 78: Chemical bonding

in biological molecules Past Papers Paper 21, June 2011, Q5 Paper 22, June 2011, Q5 (a)(b)(i) Paper 22, Nov 2011, Q4 (b)

2.2.g describe the structure of a phospholipid and relate the structure of phospholipids to their functions in living organisms Key concepts Cells as the units of life, Biochemical processes

Learners label a printed diagram showing the structure of a phospholipid molecule and discuss how the presence of polar groups relates to phospholipid behaviour when in contact with watery liquids. (W) (Basic)

Discuss the function of phospholipids in forming the bulk of structure of cell membranes, forming bilayers (link to Unit 2). (W) (Basic)

Learners do research to find out that: there are many different fatty acids and phospholipids; some phospholipids have a nitrogen-containing (choline) portion. (H) (Basic) (Challenging)

Textbooks/Publications Bio Factsheet 152: Phospholipids Past Papers Paper 21, June 2011, Q5 Paper 22, June 2011, Q5 (a)(b)(i)(ii)

(c)(d) Paper 22, Nov 2011, Q4 (b)

2.1.a (ii) carry out tests for reducing sugars and non-reducing sugars, the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins to identify the contents of solutions

Only the second part of this learning objective is included here: carry out tests emulsion test for lipids to identify the contents of solutions

Practical work, testing for lipids using the (ethanol) emulsion test. o Test vegetable oil and yellow-dyed water. (I) (Basic) o Test crushed fruits and seeds. (I) (Basic)

Practical booklet 2 is designed to be carried out after learners have used the emulsion test as described above.




http://www.biotopics.co.uk/as/lipidcondensation.html

http://www.biotopics.co.uk/as/lipidcondensation.html

http://www.chemguide.co.uk/organicprops/esters/background.html

http://www.chemguide.co.uk/organicprops/esters/background.html







V3.1 18


Key concepts Biochemical processes, Observation and experiment

Note

Ensure learners understand that lipids include triglycerides (fats and oils).



2.1.a (iii) carry out tests for reducing sugars and non-reducing sugars, the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins to identify the contents of solutions Key concepts Biochemical processes, Observation and experiment

Only the third part of this learning objective is included here: carry out tests biuret test for proteins to identify the contents of solutions.

Practical work, testing for proteins using the biuret test on a solution of egg white, skimmed milk, chicken or tofu and water. (I) (Basic)

Extension practical using a semi-quantitative biuret test: learners prepare a set of standard solutions and compare the intensity of colour obtained of an unknown with the standards (control variables). (P) (I) (Challenging)

Practical booklet 2 is designed to be carried out after learners have used the biuret test as described above.






2.3.a describe the structure of an amino acid and the formation and breakage of a peptide bond Key concepts Biochemical processes

Familiarise learners with the names of the 20 amino acids (encoded by the genetic code – see Unit 3) and their three-letter shortened version from labelled diagrams.

Learners write out the general formula of an amino acid, and on the diagrams use a colour code to identify the: R group; part common to them all; amine group; carboxylic acid group. (W) (I) (Challenging) o Learners make notes to show understanding that the ‘side-chain’ or R

(residual) group can take different forms and that the amino acids can be grouped according to the properties of their R-group. (I) (Basic)

Learners draw simple diagrams of: peptide bond formation (choose two amino acids from their diagram sheet) by condensation (add the name of the bond to

Online http://www.biotopics.co.uk/as/aa.html http://www.worldofmolecules.com/life

/ Textbooks/Publications Bio Factsheet 78: Chemical bonding

in biological molecules Bio Factsheet 80: Structure and

biological functions of proteins








http://www.biotopics.co.uk/as/aa.html

http://www.worldofmolecules.com/life/

http://www.worldofmolecules.com/life/


V3.1 19


their table of 2.3.b); hydrolysis of the dipeptide. (I) (Challenging)

Discuss how a series of condensation reactions leads to the formation of a polypeptide. (W) (Basic)

Note

The names and structures of the amino acids are not required learning.

Learners could be introduced to the one-letter abbreviations (useful for Unit 8).

Past Papers Paper 21, June 2011, Q5 Paper 22, Nov 2011, Q4 (b)

2.3.b explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) that hold these molecules in shape Key concepts Biochemical processes

Learners write down their own polypeptide, 25 amino acids long (choose from the sheet of 2.3.a) using encircled three-letter abbreviations and share with the rest of the group to highlight how an enormous number of different polypeptides can be obtained. Discuss the term primary structure. (W) (I) (Basic)

Make links forward to Unit 2 to the roles of cell structures in protein synthesis to fold / further modify the polypeptide chain. (W) (Basic)

Expand knowledge of hydrogen bonding (from 2.3.d) and 2.2.e) with an explanation of secondary structure. (W) (Basic)

Learners suggest what will hold the chain in place to form a specific 3-D structure before discussing tertiary structure. (W) (Basic) (Challenging) o Include interactions between R groups and the different types of bonding.

(W) (Basic) o Give a simple definition of quaternary structure. (W) (Basic) o Discuss how the loss of tertiary (and quaternary where it exists) results in

the loss of function of the protein. (W) (Basic) o Learners make notes on levels of organisation to highlight the relationship

between the structures and role of bonding in determining shape /stability. (I) (Challenging)

Note

For quaternary structure learners should know that this is a protein composed of more than one polypeptide chain – details of the association between chains is not required.

Do not allow learners to think that proteins with quaternary structure must be composed of four polypeptides.

Online http://www.pdb.org/pdb/home/home.

do http://www.biology.arizona.edu/bioch

emistry/tutorials/chemistry/page2.html

Past Papers Paper 21, Nov 2011, Q3 (a)

2.3.c Show diagrams/images of globular and fibrous proteins to learners for them to Online

http://www.pdb.org/pdb/home/home.do

http://www.pdb.org/pdb/home/home.do





V3.1 20


describe the molecular structure of haemoglobin as an example of a globular protein, and of collagen as an example of a fibrous protein and relate these structures to their functions (The importance of iron in the haemoglobin molecule should be emphasised. A haemoglobin molecule is composed of

two alpha () chains and two beta () chains, although when describing the

chains the terms -globin and -globin may be used. There should be a distinction between collagen molecules and collagen fibres) Key concepts Cells as the units of life, Biochemical processes

describe, and then discuss their features (include solubility) and overall roles (e.g. mainly metabolically active versus mainly structural). Discuss the fact that many fibrous proteins show little or no tertiary structure. (W) (G) (P) (I) (Basic) (Challenging)

Display a diagram / image of haemoglobin for learners to identify the features of a globular protein and consolidate knowledge of levels of protein structure. (W) (Basic) (Challenging) o Give details of haem and explain the idea of a prosthetic group. (W)

(Basic). o Notes made or construct a spider diagram / concept map relating

haemoglobin structure to function. (I) (Challenging)

With textbook/internet research, learners make bullet-pointed notes on collagen structure (include the difference between a molecule and a fibre), linking to its function (including role in blood vessel structure – link to Unit 4). (W) (I) (Basic)

Learners construct a comparison table showing the similarities and differences between haemoglobin and collagen. (F)

Compile a set of multiple choice questions from past papers for learners to complete. (F)

Note

Mention that haemoglobin has a role in the carriage of carbon dioxide (for Unit 4).

http://en.wikipedia.org/wiki/Hemoglobin

Textbooks/Publications Bio Factsheet 175: Haemoglobin:

structure & function Past Papers Paper 22, June 2011, Q3 (c) Paper 21, Nov 2011, Q3 (c)

2.1.a carry out tests for reducing sugars and non-reducing sugars, the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins to identify the contents of solutions Key concepts Biochemical processes, Observation and experiment

Practical investigation, without using instructions, to analyse the biochemicals in a range of unknown solutions or liquefied solid foods. (F)

Practical booklet 2 is a suitable protocol (designed to develop skills for Paper 3).




otes.html Textbooks/Publications King p.19-22 Siddiqui p.56-60,










V3.1 21


Bio Factsheet 173: How to identify foods: Food Tests and Chromatography

6.1.a describe the structure of nucleotides, including the phosphorylated nucleotide ATP (structural formulae are not required) Key concepts Biochemical processes, DNA, the molecule of heredity

Draw a labelled diagram of a nucleotide to show the three components: phosphate, pentose sugar and nitrogenous organic base (e.g. using a circle, pentagon and rectangle) for learners to reproduce without help. (W) (I) (Basic)

Give out images of the structural formulae of the four RNA and four DNA nucleotides, ensuring learners know the names of the bases and explaining carbon atom numbering. (W) (Basic) o In a small group, learners interpret how the diagram of a nucleotide has

been derived and identify similarities and differences between the DNA and RNA nucleotides. (G) (Basic) (Challenging)

o Learners draw a labelled generalised RNA and a DNA nucleotide, naming the different pentose sugars and indicating the four different bases for each. (I) (Basic)

Discuss briefly an image of the structural formula of ATP and agree it is a phosphorylated nucleotide before learners draw a simple diagrammatic, annotated version. Include the concept that on removal of a phosphate, energy is released (links with 1.2.c and idea of activated nucleotides for 6.1.c and 6.2.d). (W) (I) (Basic)

Introduce DNA base-pairing for 6.1.b by showing learners structural /skeletal formulae and diagrammatic forms. (W) (Basic) o Allow learners to volunteer that in the diagrams: A and G are the same

‘length’ and are ‘longer’ than T and C (also the same length) as they are double ring structures; the end where the pairs meet shows a complementary nature (e.g. A pointed, T ‘V’ shaped; G convex, C concave).

o Introduce the concept of complementary base pairing and hydrogen bonding between base pairs (mention also RNA/DNA base-pairing).

Note

Base names must be spelt correctly, e.g. thymine not thiamine, and learners must be clear about the difference between adenine and adenosine.

Emphasise that the structural/skeletal formulae of the bases is not required.

Online http://hyperphysics.phy-

astr.gsu.edu/hbase/biology/atp.html Textbooks/Publications Bio Factsheet 129: ATP – what it is,

what it does. Past Papers Paper 23, Nov 2011, Q5 (a)

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/atp.html

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/atp.html


V3.1 22


6.1.b describe the structure of RNA and DNA and explain the importance of base pairing and the different hydrogen bonding between bases (include reference to adenine and guanine as purines and to cytosine, thymine and uracil as pyrimidines. Structural formulae for bases are not required but the recognition that purines have a double ring structure and pyrimidines have a single ring structure should be included) Key concepts Biochemical processes, DNA, the molecule of heredity

Discuss phosphodiester bond (strong, covalent) formation by condensation reactions to produce a polynucleotide (learners add the bond name to their table of 2.2.b). (I) (Basic)

Learners prepare cut-out nucleotides and, with verbal prompts, build up a short polynucleotide strand, learning about the sugar-phosphate backbone and noting the variation in sequences among the class (different ‘information’). (P) (I) (H) (Basic)

Explain the concept of ‘direction’ of the strand (5′ to 3′) before learners build up the anti-parallel complementary strand (see final activity 6.1.a). (P) (I) (Challenging) o Point out how base pairing allows the strands to be parallel and the

strength of having many hydrogen bonds (from single weak H bonds). (W) (Basic)

Groups of learners can join together their sections to give the idea of a (short!) gene and the class can see each gene carries different information to code for different proteins. (W) (G) (Basic)

Learners fully label and annotate pre-existing diagrams of DNA. (I) (Basic)

Extension activity (see website recommended): learners read about the discovery of DNA. (I) (Challenging)

Progress to RNA structure, giving an outline of the three types of RNA before learners make notes, including diagrams. (W) (I) (Basic)

Learners construct a summary table of the similarities and differences between DNA and RNA. (F)

Summary discussions (small group and class) about requirements of the ideal molecule of inheritance, resulting in a large poster. (W) (G) (Basic) (Challenging) o Carrying information to allow proteins to be synthesised (sequence of

nucleotides). o Expression to obtain the proteins (transcription and translation, learned

later). o Stability (strong sugar-phosphate backbone, many H bonds). o Faithful replication to pass on information to daughter cells

(complementary nature of the strands). o Ability to provide variation (mutations, learned later).

Note

Save the nucleotides for DNA replication in Unit 3.

Online http://www.dnaftb.org http://www.hhmi.org/biointeractive/dn

a/index.html http://www.ncbe.reading.ac.uk/ncbe/

PROTOCOLS/DNA/extracting.html http://learn.genetics.utah.edu/content

/labs/extraction/ http://www.nature.com/nature/dna50/

archive.html Past Papers Paper 21, June 2011, Q3 Paper 21, June 2012, Q6 (a)

http://www.dnaftb.org/

http://www.hhmi.org/biointeractive/dna/index.html

http://www.hhmi.org/biointeractive/dna/index.html

http://www.ncbe.reading.ac.uk/ncbe/PROTOCOLS/DNA/extracting.html

http://www.ncbe.reading.ac.uk/ncbe/PROTOCOLS/DNA/extracting.html

http://learn.genetics.utah.edu/content/labs/extraction/

http://learn.genetics.utah.edu/content/labs/extraction/

http://www.nature.com/nature/dna50/archive.html

http://www.nature.com/nature/dna50/archive.html


V3.1 23


3.1.a explain that enzymes are globular proteins that catalyse metabolic reactions Key concepts Cells as the units of life, Biochemical processes

Brainstorm or provide multiple choice questions to gauge learner knowledge, including understanding of the terms globular, metabolic and catalyst. Emphasise that previous studies will be extended and name some enzymes they will learn about e.g. DNA polymerase and carbonic anhydrase. (W) (Basic)

State that most enzyme names end with ‘ase’ and discuss the role of enzymes, e.g. synthesising macromolecules; transferring groups such as phosphates; rearranging molecules to form different ones. (W) (Basic).

Online http://highered.mcgraw-

hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html

Textbooks/Publications Bio Factsheet 163: Answering

Questions: enzyme activity. Past Papers Paper 23, Nov 2013, Q6 (c)

3.1.b state that enzymes function inside cells (intracellular enzymes) and outside cells (extracellular enzymes) Key concepts Cells as the units of life, Biochemical processes

Explain that enzymes are produced within cells. Learners volunteer the meanings of ‘intra-‘ and ‘extra- ‘and discuss these with respect to enzymes that remain to function intracellularly and others that are released to act extracellularly (e.g. digestive enzymes) (this links later to role of the Golgi body). (W) (Basic)

Note

Learners will benefit if they know the meaning of prefixes e.g. intra, extra, poly, milli, mono. Explain that some have the same meaning but Latin or Greek origins (e.g. uni versus mono).

Textbooks/Publications Bio Factsheet 24: Human digestion.

3.1.c explain the mode of action of enzymes in terms of an active site, enzyme/substrate complex, lowering of activation energy and enzyme specificity (the lock and key hypothesis and the induced fit hypothesis should be included) Key concepts

Learners make notes on the mode of action of enzymes (remind them of protein structure), highlighting structure to function. (I) (Challenging) o Describe and explain enzyme structure, including the active site. o Include a set of annotated diagrams of the lock and key and induced fit

mechanisms (noting the role of the R groups of amino acids at the active site in binding with the substrate).

o Explain that many/most reactions can be catalysed in both directions.

Learners use paper cut-out models to show how enzymes can break up substrates into smaller molecules or can build up larger molecules from smaller ones. (P) (I) (Basic)

Online http://highered.mcgraw-

hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html


http://www.learnerstv.com/animation/animation.php?ani=161&cat=Biolog

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html














http://www.learnerstv.com/animation/animation.php?ani=161&cat=Biology



V3.1 24


Biochemical processes Discuss the concept of lowering activation energy. (W) (Challenging) o Learners annotate a ‘boulder analogy’ graph to highlight that, although the

energy content of substrate and products is not changed, the reaction pathway follows a lower energy course. (H) (Basic)

o Learners summarise a discussion about the different ways activation energy can be lowered by adding notes to their diagrams or the graph. (I) (Challenging)

Note

Use the term ‘complementary’ to describe how the substrate fits into, and binds at, the active site. ‘Matches’ is incorrect.

Check understanding of the term substrate - some may have used the term reactant.

y Past Papers Paper 23, Nov 2013, Q6 (c)

3.1.d investigate the progress of an enzyme-catalysed reaction by measuring rates of formation of products (for example, using catalase) or rates of disappearance of substrate (for example, using amylase) Key concepts Biochemical processes, Observation and experiment

Explain that the course of an enzyme-catalysed reaction can be shown by substrate disappearance or product formation over time. (W) (Basic)

Emphasise that a rate measurement is given per unit time and that there will be a change in the rate during the course of the reaction. (W) (Basic)

Learners carry out practical work using catalase (e.g. from yeast, potato, celery, lettuce) to investigate the rate of release of oxygen (product) from hydrogen peroxide (substrate). (W) (G) (P) (I) (H) (Basic) (Challenging) o A graph should be constructed of volume produced (or mass lost if using

an electronic balance) over time intervals. o Use the graph to calculate initial rate and explain the initial steep release

of product, which then flattens out.

Practical booklet 5. Learners carry out practical work using amylase to time how long it breaks down starch. Remind learners that using iodine (in potassium iodide) solution on samples shows the loss of starch from the reaction mixture over time. This practical is designed to develop practical skills (itemised in the Teacher’s practical notes) assessed in Paper 3. (W) (G) (P) (I) (H) (Basic)

Extend practical using amylase if a colorimeter is available to get quantitative results. Trials are required to ensure that the colour of resulting solutions is not too intense for the colorimeter for a graph. (P) (I) (Challenging)

Practical booklet 4 (carry out after Practical booklet 5) is a modification of the method described above using catalase.

Practical booklets 4, 5 Online http://www.practicalbiology.org/areas/

advanced/bio-molecules/factors-affecting-enzyme-activity/investigating-an-enzyme-controlled-reaction-catalase-and-hydrogen-peroxide-concentration,47,EXP.html

www.csub.edu/~kszick_miranda/Enzymes%20part2.doc

http://www.saps.org.uk/secondary/teaching-resources/293-learner-sheet-24-microscale-investigations-with-catalase

Textbooks/Publications Bio Factsheet 130: Investigating

catalase Past Papers Paper 21, Nov 2011, Q2 (a)


http://www.practicalbiology.org/areas/advanced/bio-molecules/factors-affecting-enzyme-activity/investigating-an-enzyme-controlled-reaction-catalase-and-hydrogen-peroxide-concentration,47,EXP.html







http://www.csub.edu/~kszick_miranda/Enzymes%20part2.doc

http://www.csub.edu/~kszick_miranda/Enzymes%20part2.doc

http://www.saps.org.uk/secondary/teaching-resources/293-student-sheet-24-microscale-investigations-with-catalase





V3.1 25


3.2.a investigate and explain the effects of the following factors on the rate of enzyme-catalysed reactions:

Temperature

pH (using buffer solutions)

enzyme concentration

substrate concentration

inhibitor concentration Key concepts Organisms in their environment

With prompting, learners explain why measuring the time taken for complete removal of substrate is unsuitable if trying to measure the effect of substrate concentration (with more substrate the rate of reaction is faster, but it takes longer for it all to disappear). (W) (I) (Challenging)

Discuss with learners why, ideally, initial rates should be calculated when comparing enzyme activity under different conditions. (W) (Challenging)

Develop planning skills: learners design an investigation in which several variables need to be controlled and carry this out (ensure that a range of plans is covered). (W) (I) (Basic) (Challenging)

Learners carry out practical activities on factors affecting the rate of an enzyme-catalysed reaction (examples below). (P) (I) (Basic) (Challenging) o Effect of temperature: the catalase experiment in 3.1.d. o Effect of pH: use trypsin to digest protein in a suspension of milk powder. o Effect of enzyme concentration or substrate concentration: use amylase or

diastase to digest a starch suspension. Then learners present their results and contribute to whole class discussion, following up with a written explanation. Construct and annotate graphs showing: o the impact of rate of collisions (temperature, substrate concentration,

enzyme concentration). o the effect on hydrogen bonding, tertiary structure, shape of active site and

complementary fit of substrate (temperature, pH, inhibitors). (W) (I) (Basic) (Challenging)

Possibly demonstrate a practical that uses inhibitors considered to be hazardous to the environment (minimises the volumes used). Check your local authority regulations concerning safe disposal.

Note

Ensure learners can interpret correctly graphs with the same shaped curve, e.g. course of an enzyme-catalysed reaction / the effect of increasing substrate concentration on the rate of a reaction.

For inhibitor concentration, 3.2.b should be covered first or incorporate this part of 3.2.a with 3.2.b.

To show that an inhibitor is competitive is difficult as separate reaction mixtures with different concentrations of the substrate need to be made up.

Practical booklet 5 Online http://www.ncbe.reading.ac.uk/NCBE

/PROTOCOLS/menu.html http://www.ncbe.reading.ac.uk/NCBE

/PROTOCOLS/juice.html http://www.saps.org.uk/secondary/te

aching-resources/95-investigating-the-effect-of-competitive-and-non-competitive-inhibitors-on-the-enzyme-ss-galactosidase

http://www.southernbiological.com/ http://www.saps.org.uk/secondary/te

aching-resources/261-the-inhibition-of-catechol-oxidase-by-lead

Textbooks/Publications King p.64-68 Siddiqui p.69-75. Bio Factsheet 43: Factors affecting

enzyme activity Past Papers Paper 21, June 2011, Q4 Paper 32, June 2013, Q1

3.2.b Explain Vmax and Km (great detail not required) before learners make notes. Online

http://www.ncbe.reading.ac.uk/NCBE/PROTOCOLS/menu.html

http://www.ncbe.reading.ac.uk/NCBE/PROTOCOLS/menu.html

http://www.ncbe.reading.ac.uk/NCBE/PROTOCOLS/juice.html

http://www.ncbe.reading.ac.uk/NCBE/PROTOCOLS/juice.html

http://www.saps.org.uk/secondary/teaching-resources/95-investigating-the-effect-of-competitive-and-non-competitive-inhibitors-on-the-enzyme-ss-galactosidase





http://www.southernbiological.com/

http://www.saps.org.uk/secondary/teaching-resources/261-the-inhibition-of-catechol-oxidase-by-lead




V3.1 26


explain that the maximum rate of reaction (Vmax) is used to derive the Michaelis-Menten constant (Km) which is used to compare the affinity of different enzymes for their substrates Key concepts Biochemical processes, Observation and experiment

(W) (I) (Basic) o Show learners how to obtain Vmax and Km from a graph. o Learners arrive at the idea that the enzyme is saturated with substrate at

the maximum rate of reaction, Vmax. o Show learners how to obtain Km from a graph, the concentration of

substrate that enables the enzyme to achieve half the maximum rate of reaction, or half Vmax

Learners obtain (Vmax) and (Km) using one of the graphs constructed from their practical work. (I) (Basic)

Extend learner understanding of Km by discussion or a worksheet providing some information accompanied by questions. (W) (I) (Challenging) o Explain that (Km) is the affinity of enzyme for its substrate. o Allow learners to suggest that an enzyme with a low Km

has a high affinity for its substrate needs a lower concentration of substrate to reach Vmax than an

enzyme with a high Km. o Explain that an enzyme with a low Km is more likely to be saturated with

substrate in the normal conditions of substrate within a cell, so variations in substrate will have less effect on the rate of formation of product.

o Ask learners to explain why an enzyme with a high Km is likely to vary its activity more (i.e. the concentration of substrate becomes more important).

Learners sketch out two graphs to show the differences between an enzyme with a high Km and an enzyme with a low Km o Annotate graphs with explanations. (I) (Challenging)

http://www.worthington-biochem.com/introbiochem/substrateConc.html

3.2.c explain the effects of reversible inhibitors, both competitive and non-competitive, on the rate of enzyme activity Key concepts Biochemical processes

Following class discussion, learners use resources to make notes and annotated diagrams about enzyme inhibition. (I) (Challenging) o Draw graphs of increasing substrate concentration with and without

inhibitors.

Learners construct a summary table showing the differences between competitive and non-competitive inhibition (include the different graphs). (I) (Challenging)

Extension activity: learners investigate and discuss the use of inhibitors as medicinal drugs, including the different uses of competitive versus non-competitive inhibitors. (G) (P) (I) (Challenging)

Online http://www.wiley.com/college/boyer/0

470003790/animations/enzyme_inhibition/enzyme_inhibition.htm

Textbooks/Publications Bio Factsheet 31: Enzyme control of

metabolic pathways. Past Papers Paper 21, Nov 2011, Q2 (b)




http://www.wiley.com/college/boyer/0470003790/animations/enzyme_inhibition/enzyme_inhibition.htm




V3.1 27


Note

Irreversible inhibition and allosteric regulation could be worth mentioning briefly when covering 3.2.c.

3.2.d investigate and explain the effect of immobilising an enzyme in alginate on its activity as compared with its activity when free in solution Key concepts Observation and experiment

Practical: ‘Better milk for cats’ or similar protocol using a different enzyme. o Discuss how immobilised enzymes are used in everyday applications. (W)

(Basic) o Introduce the use of dipsticks containing glucose oxidase (useful for

14.1.k). (W) (Basic)

Demonstrate the same enzymatic reaction using the enzyme free in solution. Learners suggest the advantages of immobilising the enzyme rather than using it free (not immobilised) and summarise with a comparison table. (W) (Challenging)

Extension practical: learners use immobilised yeast cells to investigate the effectiveness of their sucrase or catalase enzymes. (P) (I) (Challenging)

Learners complete a worksheet prepared by you to interpret and compare graphical and tabulated data for immobilised enzymes with free enzymes. o Data extraction to compare both for the following factors: temperature; pH;

substrate concentration; inhibitor presence. o Learners consider explanations of the differences between free and

immobilised enzymes, e.g. protective and stabilising effect of the alginate matrix; degradation over time; active sites of immobilised enzymes may not all be available; time taken for diffusion to occur; possibility of slightly altered active site shape when immobilised, amongst others. (I) (Challenging)

Note

Experiment and observation, a key concept, has increasingly been used to develop biotechnological applications – here learners can appreciate how biological systems can be used to benefit humans in the everyday world.

Learners should know the method to prepare alginate beads.

Online http://www.rpi.edu/dept/chem-

eng/Biotech-Environ/IMMOB/Immob.htm

http://www1.lsbu.ac.uk/water/enztech/imeconom.html

Textbooks/Publications King p.69-73 Siddiqui p.72-73 Bio Factsheet 148: Industrial uses of

enzymes. Past Papers Paper 32, June 2012, Q1 (b) Paper 43, June 2011, Q2 Paper 43, Nov 2011, Q2 (b)

http://www.rpi.edu/dept/chem-eng/Biotech-Environ/IMMOB/Immob.htm






V3.1 28

Unit 2: Cells as the basic units of life


Little prior knowledge is required but a basic knowledge of cell structure and practical knowledge of the light microscope would be helpful. The ability to carry out simple mathematical calculations is required. Learners should understand kinetic theory (http://www.chemguide.co.uk/physical/kt/basic.html is a good basic introduction). If Unit 1, Biological molecules, is taught after this unit, some knowledge of lipids, proteins and carbohydrates is useful. Context

Unit 1, Biological molecules, leads on to an understanding of the structure of cells and the functions of cell structures, including biological membranes. This unit deals with topics that are fundamental to almost every area of study covered in the AS and A Level course. Cell structure, and the functions of the various organelles, will reappear in numerous contexts. Learners should appreciate the key concept that cells are the basic unit of life and that all living organisms are composed of one or more cells. Learners will need to be reminded, or taught, how to use a light microscope. An understanding of how substances are transported across membranes is essential reference material for other topics in this syllabus, especially those covering plant and animal physiology. Outline

Early on, learners are introduced to the use of the microscope in cell studies, including use of the graticule and micrometer to measure cells. Calculations of magnification and actual sizes are included in this unit. This unit covers the two fundamental types of cell, eukaryotic and prokaryotic. Details of cell structure are studied, including the functions of organelles. The fluid mosaic model of membrane structure highlights how membranes can fulfil their roles. The role of the membrane in cell signalling is introduced. The unit also covers the different mechanisms that enable the movement of substances into and out of cells. Teaching time


http://www.chemguide.co.uk/physical/kt/basic.html


V3.1 29


1.1.d explain and distinguish between resolution and magnification, with reference to light microscopy and electron microscopy Key concepts Observation and experiment

Show images of both microscope types and agree more detail can be obtained about cells / cell structure using microscopes. (W) (Basic)

Agree the meaning of magnification – learners write a worded version and link this later to the formula used in 1.1.c. Explain how the overall magnification is obtained (eyepiece x objective lens). (W) (Basic)

Introduce resolution, explaining why the resolution of electron microscopes is much higher than that of light microscopes (only enough detail of the workings of each to help understanding of resolution). (W) (Basic) (Challenging) o Explain that detail smaller than 200nm (approximately half the wavelength

of light) cannot be resolved by the light microscope. (W) (Challenging)

Explain that increasing magnification is only desirable up to the limit of resolution, e.g. up to approx. x 1000 for the light microscope (electron microscopes vary considerably).

Compare the TEM and SEM (no details of working required) and the micrographs produced, so learners see the difference between, and usefulness of, both.

Learners suggest advantages and disadvantages of the two types of microscope. (G) (Basic)

Learners observe a range of photomicrographs and electron micrographs and explain which type of microscope was used to produce the image. If these have a mixture of magnifications and scale bars on them, they can be used in 1.1.e. (G) (P) (Basic)

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=10 http://www.vcbio.science.ru.nl/en/virtuallessons/#fesemsimulatie http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells2.html http://zeiss-campus.magnet.fsu.edu/articles/basics/index.html Textbooks/Publications King p.39-41 Bio Factsheet 75: Microscopes and

their uses in Biology Past Papers Paper 21, June 2012, Q2 (a) Paper 22, June 2013, Q2 (b) Paper 22, Nov 2012, Q1 (a)

1.1.a compare the structure of typical animal and plant cells by making temporary preparations of live material and using photomicrographs Key concepts Cells as the units of life, Observation and experiment

Practical: learning how to use the light microscope. (I) (Basic) (Challenging)

Brainstorm knowledge of the plant cell structure and animal cell structure and discuss cells as the units of life. (W) (Basic)

Learners construct a comparison table, generalised animal cell v generalised plant cell, the first row containing simple labelled diagrams. (I) (Basic) (Challenging)

Practical: learners make a temporary preparation, check and give comments on technique and slides made of peers. (I) (Basic) (Challenging)

Discuss the slides and compare with the constructed table (links to the ideas in 1.1.d). (W) (Basic)

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=10 Textbooks/Publications Siddiqui p.28-29

http://www.biology4all.com/resources_library/details.asp?ResourceID=10


http://www.vcbio.science.ru.nl/en/virtuallessons/#fesemsimulatie


http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells2.html


http://zeiss-campus.magnet.fsu.edu/articles/basics/index.html






V3.1 30


Note

This may be combined with 1.1.c and 1.1.e.

Diagram-drawing skills may be introduced here.

1.1.c use an eyepiece graticule and stage micrometer scale to measure cells and be familiar with units (millimetre, micrometre, nanometre) used in cell studies Key concepts Cells as the units of life, Observation and experiment

Revise the units of length commonly used during the course (see 1.1.c) with the metre (meter US) as the SI unit of length.

o Learners to perform conversions between nm, m, mm and m. (W) (Basic)

Explain how to use a stage micrometer to calibrate an eyepiece graticule. (W) (Challenging) o Practical booklet 1 is designed to develop the skills required by learners

(see Teacher’s practical notes) when measuring using an eyepiece graticule and a stage micrometer.

o If learners always use the same microscope, then they can calibrate once only for each objective lens, and keep a record of it. (I) (Challenging)

o Learners use the Bioscope to learn the principles of use. (I) (Challenging)

Learners use their calibrated eyepieces to measure a range of microscopic specimens, choosing one specimen to draw (see 1.1.a). (I) (Basic) (Challenging) o Learners measure the actual length of a part of a specimen on the slide

and by measuring the length drawn on their diagram, they can calculate the linear magnification of their drawing. (I) (Basic)

Note

Discourage measuring in cm as many forget to multiply by 10 to convert to

mm before converting to m.

The eyepiece graticules can be fitted permanently into the eyepiece of the microscope.

Inexpensive stage micrometer scale kits and eyepiece graticules can be obtained from the Cambridge publications catalogue www.cie.org.uk/cambridge-for/teachers/order-publications

Practical booklet 1 CD-ROM Bioscope – teaching and learning

tool for the skills required to use a graticule and stage micrometer successfully.

Online http://learn.genetics.utah.edu/content/cells/scale/ http://www.biology4all.com/resources_library/details.asp?ResourceID=10 http://www.vcbio.science.ru.nl/en/virtuallessons/#fesemsimulatie http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells2.html http://zeiss-campus.magnet.fsu.edu/articles/basics/index.html Textbooks/Publications King p.20-22 Siddiqui p.42-43 Past Papers Paper 31, Nov 2012, Q2 (b)(c) Paper 33, Nov 2012, Q2 (b) Paper 35, Nov 2012, Q2 (b) Paper 12, Nov 2011, Q5

1.1.b Hold up an apple, then drawings of the apple: at the same size = Past Papers

http://www.cie.org.uk/cambridge-for/teachers/order-publications

http://learn.genetics.utah.edu/content/cells/scale/

http://learn.genetics.utah.edu/content/cells/scale/











V3.1 31


calculate the linear magnifications of drawings, photomicrographs and electron micrographs Key concepts Observation and experiment

magnification x 1; double the size = x 2; half the size = x 0.5. Discuss the mental calculation learners have made to get the right answer. o magnification = image size / actual size. (Group) (Basic)

Explain how to use scale bars to calculate magnification, emphasising that learners should measure the scale bar length and not the image. (W) (Challenging)

Learners complete a worksheet prepared by you with images of varying stated length (nm to mm) and with scale bars only. Use copyright-free images to prepare the worksheet (e.g. Wikipedia). (P) (I) (Basic) (Challenging)

Paper 22, June 2011, Q4 (b) Paper 21, June 2011, Q1 (a) Paper 23, Nov 2011, Q1 (a) Paper 31, June 2011, Q2 (c)

1.1.e calculate actual sizes of specimens from drawings, photomicrographs and electron micrographs Key concepts Observation and experiment

Discuss how the actual sizes can be calculated using the rearranged formula to calculate magnifications. (W) (Basic) o Explain also how to use scale bars to calculate actual sizes. (W) (Basic) o Learners calculate actual sizes from diagrams and the photomicrographs

and electron micrographs from 1.1.d using the given scale bar or magnification. (P) (I) (Basic) (Challenging)

Learners tackle worksheets prepared by you with exam-style (differentiated) questions to calculate actual sizes and magnifications (use past papers). (I) (H) (F) (Basic) (Challenging)

Online http://www.cellsalive.com/howbig.htm Past Papers Paper 21, Nov 2011, Q5 (a)

1.2.b recognise the following cell structures and outline their functions:

cell surface membrane

nucleus, nuclear envelope and nucleolus

rough endoplasmic reticulum

smooth endoplasmic reticulum

Golgi body (Golgi apparatus or Golgi complex)

mitochondria (including small circular DNA)

ribosomes (80S in the cytoplasm and 70S in chloroplasts and mitochondria)

Interactive session using diagrams and electron micrographs: agree descriptions of the cell structures and discuss their functions. o With reference to plant and animal cells, introduce the terms eukaryote

and eukaryotic, explaining the meaning of ‘true nucleus’. (W) (Basic)

Provide an overview of how different cell structures are linked, e.g. outline sequence of events in protein production and secretion. (W) (Basic)

Learners identify particular cell structures and state their function using electron micrographs and photomicrographs, at various magnifications. Include examples of both plant and animal cells (names of cell types not required). (G) (P) (I) (Basic) (Challenging)

Learners label the cell structures on diagrams drawn from electron micrographs of both plant cell and animal cells, and annotate each with a function. (F)

Note

Online http://publications.nigms.nih.gov/insidethecell/chapter1.html http://www.cellsalive.com/cells/cell_model.htm http://learn.genetics.utah.edu/content/cells/insideacell/ http://www.bscb.org/?url=softcell/index http://cellpics.cimr.cam.ac.uk/ http://library.med.utah.edu/WebPath/HISTHTML/EM/EM006.html Textbooks/Publications Bio Factsheet 4: Structure to function

http://www.cellsalive.com/howbig.htm

http://publications.nigms.nih.gov/insidethecell/chapter1.html

http://publications.nigms.nih.gov/insidethecell/chapter1.html

http://www.cellsalive.com/cells/cell_model.htm

http://www.cellsalive.com/cells/cell_model.htm

http://learn.genetics.utah.edu/content/cells/insideacell/


http://www.bscb.org/?url=softcell/index

http://www.bscb.org/?url=softcell/index

http://cellpics.cimr.cam.ac.uk/

http://library.med.utah.edu/WebPath/HISTHTML/EM/EM006.html



V3.1 32


lysosomes

centrioles and microtubules

chloroplasts (including small circular DNA)

cell wall

plasmodesmata

large permanent vacuole and tonoplast of plant cells

Key concepts Cells as the units of life, Biochemical processes, DNA, the molecule of heredity

Learners should understand (no definition required) that an organelle is a structure within a cell that has a function.

Discuss the idea of the advantages of cellular compartments.

For mitochondria and chloroplasts see also 1.2.c.

in eukaryotic cells. Past Papers Paper 22, Nov 2011, Q6 (a) Paper 21, June 2012, Q2 (b)(c)(e)

1.2.c state that ATP is produced in mitochondria and chloroplasts and outline the role of ATP in cells Key concepts Biochemical processes

Extend 1.2.b so learners know that ATP is produced: in chloroplasts as a result of the absorption of light; in mitochondria in aerobic respiration. (W) (Basic)

Discuss why a cell needs energy and the need for energy transfers within a cell. (W) (Basic) o Explain that ATP is the molecule used for these transfers and is described

as the universal energy currency of the cell. o Stress that ATP is not a form of energy but that energy is released when

ATP is hydrolysed and this energy can be used by the cell.

Note

This sets the scene for other learning objectives, e.g. 4.2.a, 12.1.a, 12.1.b, 13.1.f, 13.1.h and 15.1e, so do not be tempted to give too many details at this stage.

Online http://www.biologyinmotion.com/atp/index.html Textbooks/Publications Bio Factsheet 129: ATP–what it is,

what it does.

1.2.a describe and interpret electron micrographs and drawings of typical animal and plant cells as seen with the electron microscope

Emphasise that although cells are the basic unit of life, they can have different structures depending on their function. (W) (Basic)

State that membranes range from approximately 5-9 nm thick and allow learners to explain that the boundary of the cell /nucleus is only seen with the light microscope because of the contrast (membranes are not visible). (W) (Challenging)

Online http://micro.magnet.fsu.edu/primer/techniques/contrast.html http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMAtlas.html

http://www.biologyinmotion.com/atp/index.html

http://www.biologyinmotion.com/atp/index.html

http://micro.magnet.fsu.edu/primer/techniques/contrast.html

http://micro.magnet.fsu.edu/primer/techniques/contrast.html

http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMAtlas.html




V3.1 33


Key concepts Cells as the units of life

o Learners volunteer that detail such as membranes are visible using the electron microscope. (W) (Basic)

From electron micrographs of different cell types, learners can identify: o whether plant or animal, stating the features that enabled the choice, o all the cell structures seen, adding labels and annotations.

(P) (I) (H) (F) (Basic) (Challenging)

Extension activity: learners compare electron micrograph images and drawings with those obtained with the light microscope. (P) (I) (Basic) (Challenging) o Learners construct a descriptive list of the additional features seen. (G)

(P) (Basic)

http://learn.genetics.utah.edu/content/cells/insideacell/ Past Papers Paper 21, June 2012, Q2 Paper 22, Nov 2012, Q1 (b)

1.2.d outline key structural features of typical prokaryotic cells as seen in a typical bacterium (including: unicellular, 1-

5m diameter, peptidoglycan cell walls, lack of organelles surrounded by double membranes, naked circular DNA, 70S ribosomes) Key concept Cells as the units of life

Short answer test to revise plant and animal cell structural details. (F)

Linking to the key concept of cells as the units of life, explain to learners that there are two fundamental types of cell: eukaryotic and prokaryotic. o Explain how the term ‘prokaryotic’ arose. o Discuss how the single cell comprising a unicellular organism will exhibit

all the characteristics that define life. (W) (Basic)

Build up a typical bacterial cell (example of a prokaryote) by introducing each key structural feature in turn (e.g. overhead transparency overlays/PowerPoint slides). (W) (Basic)

From 1.2.b, learners suggest functions of prokaryotic structures. (I) (Challenging)

Learners label a diagram, or draw a labelled diagram, of a typical bacterium / prokaryote. (I) (Basic) (Challenging)

Annotate the diagram with an outline function. (H) (Basic)

Note

Reference could be made to the bacteria responsible for cholera and TB (see Unit 5).

Archaea as prokaryotes are covered in Unit 7.

You could mention (to prepare for Unit 7), the kingdom Prokaryotae and the four eukaryotic kingdoms, Fungi, Protoctista, Plantae and Animalia.

Online http://www.cellsalive.com/cells/bactcell.htm http://www.ucmp.berkeley.edu/bacteria/bacteria.html Textbooks/Publications Bio Factsheet 73: The prokaryotic

cell Past Papers Paper 22, June 2011, Q4 Paper 23, Nov 2011, Q1

1.2.e Learners examine photomicrographs, electron micrographs and diagrams of



http://www.cellsalive.com/cells/bactcell.htm

http://www.cellsalive.com/cells/bactcell.htm

http://www.ucmp.berkeley.edu/bacteria/bacteria.html

http://www.ucmp.berkeley.edu/bacteria/bacteria.html


V3.1 34


compare and contrast the structure of typical prokaryotic cells with typical eukaryotic cells (reference to mesosomes should not be included) Key concepts Cells as the units of life

typical prokaryotic and eukaryotic cells. (G) (Basic) o Learners discuss the major differences between the two cell types. (G)

(Basic) o Learners give a bullet-point list of similarities and construct a table of

differences. (I) (Challenging)

Note

Mention to learners that mesosomes (in many textbooks) are now considered to be artefacts from preparation for electron microscopy.

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=52 Textbooks/Publications Bio Factsheet 107: Answering exam

questions – cells Past Papers Paper 23, Nov 2011, Q1 (b)

1.2.f outline the key features of viruses as non-cellular structures (limited to protein coat and DNA/RNA) Key concepts Cells as the units of life, Biochemical processes, DNA, the molecule of heredity

Outlining the key features of viruses for learners to produce annotated diagrams. (W) (I) (Basic)

Learners investigate a range of viruses. (H) o A follow-up discussion/debate about viruses as complex entities that do

not fit the cell theory of life (also applies understanding of the key concept of cells as the units of life – are viruses living organisms?). (W) (Challenging)

Note

Mention that some viruses have an additional outer envelope similar in nature to a cell surface membrane (preparation for HIV in Unit 5).

Past Papers Paper 21, June 2012, Q6 (c)

4.1.a describe and explain the fluid mosaic model of membrane structure, including an outline of the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins Key concepts Cells as the units of life, Biochemical processes

Learners make protein, cholesterol and phospholipid (mix of fatty acid tails – both, saturated and unsaturated or one of each) cut-outs from templates provided by you. (H) (Basic)

Learners complete a short test to recall knowledge of phospholipids, proteins and carbohydrates. Go through this and make links to membrane structure. (F) (Challenging) o For a phospholipid, use a symbolised or molecular model to point out the

hydrophilic phosphate ‘head’ portion and the two hydrophobic hydrocarbon tails (fatty acid residues).

o Relate protein structure to the main membrane protein types e.g. enzymes (globular); channel (lining of amino acids with hydrophilic R groups), etc.

o Describe carbohydrate portions of glycolipids and glycoproteins as chains of sugar molecules.

Online http://www.saps.org.uk/secondary/teaching-resources/754-using-beetroot-in-the-lab www.ultranet.com/~jkimball/BiologyPages/C/CellMembranes.html http://www.wisc-online.com/objects/ViewObject.aspx?ID=ap1101 http://www.stolaf.edu/people/giannini/flashanimat/lipids/membrane%20fluidity.swf



http://www.saps.org.uk/secondary/teaching-resources/754-using-beetroot-in-the-lab



http://www.ultranet.com/~jkimball/BiologyPages/C/CellMembranes.html

http://www.ultranet.com/~jkimball/BiologyPages/C/CellMembranes.html

http://www.wisc-online.com/objects/ViewObject.aspx?ID=ap1101



http://www.stolaf.edu/people/giannini/flashanimat/lipids/membrane%20fluidity.swf




V3.1 35


Discuss the basic model to describe the structure of membranes, explaining that the physical boundary is based on phospholipids. (W) (Challenging) o Draw a line indicating a water/air boundary and a diagram of a symbolised

phospholipid. Learners suggest how phospholipids would behave if they were spread as monolayer (tails in the air, heads in water).

o Discuss the behaviour of phospholipids immersed in water (spheres, heads out, tails to centre, natural self-assembly).

o Highlight the idea of a ‘fluid’ phospholipid bilayer forming a compartment (e.g. cell/membranous organelle) and discuss which substances could cross the hydrophobic core.

o Discuss the scattered (hence ‘mosaic’) proteins and their various overall roles, e.g. enzymes, receptors for binding ligands, and the transport of polar molecules and ions.

o Mention interspersed cholesterol molecules (lipids).

Learners use their cut-outs to build a section of a membrane, noting the larger gaps when phospholipids with unsaturated fatty acid tails occur within the bilayer. (P) (I) (Basic)

Discuss and explain factors affecting membrane fluidity, including: the role of unsaturated and saturated fatty acids; how cholesterol acts to regulate; temperature. (W) (Challenging)

Learners label the different membrane components on a range of different diagrams (prepared by you) of the fluid-mosaic model. (I) (Basic).

Learners make notes to explain why the fluid mosaic model is an appropriate term to use. (I) (Basic)

Link the presence of glycolipids and glycoproteins to the cell surface membrane and outline their roles. (W) (Basic)

Learners practise drawing a labelled diagram of a section of a membrane that can be completed under exam conditions in 3-4 minutes. (I) (F) (Challenging) o Learners can annotate with the roles of the components. (F)

Note

Learners should know the terms given in the notes in 2.3.d (Unit 1) to explain transport of substances across the phospholipid bilayer or using membrane proteins.

Textbooks/Publications Bio Factsheet 8: The cell surface

membrane. Past Papers Paper 21, Nov 2011, Q1 (a) Paper 22, Nov 2012, Q2 (a)


V3.1 36


4.1.b outline the roles of cell surface membranes including references to carrier proteins, channel proteins, cell surface receptors and cell surface antigens Key concepts Cells as the units of life, Biochemical processes

Learners suggest and list the desired features of cell surface membranes. Explain that there are some specialised cells that can engulf e.g. bacteria to introduce phagocytosis / endocytosis. (W) (I) (Basic)

Brainstorm a list of materials/substances entering and leaving cells. (W) (Basic)

Learners give a written explanation of the role of phospholipids and proteins in controlling the passage of substances across the cell surface membrane, making reference to its partially permeable nature. (I) (Challenging)

Learners research and note the differences between carrier and channel proteins (how they act to transport solutes across the membrane), and explain how aquaporins increase the membrane permeability to water. (I) (Basic)

Question and answer session revising protein structure, discussing cell surface receptors for learners to make notes. (W) (Basic) o Learners suggest / research examples of ligands, e.g. hormones,

neurotransmitters. (I) (Basic)

Outline how glycoproteins and glycolipids can act as antigens (also in Unit 5). (W) (Basic)

Learners write out a summary of this learning objective. (F)

Online http://www.biologymad.com/cells/cellmembrane.htm http://www.ncbi.nlm.nih.gov/books/NBK9847/ Past papers Paper 22, June 2013, Q4 (c)

4.1.c outline the process of cell signalling involving the release of chemicals that combine with cell surface receptors on target cells, leading to specific responses Key concepts Cells as the units of life, Biochemical processes

A reminder of cell receptors introduces the idea of cell signalling. (W) (Basic)

Learners draw one or more annotated diagrams to show the general sequence of events occurring in cell signalling. (I) (Challenging)

Extension work: learners apply knowledge to specific examples. (I) (Challenging)

Online http://www.open.edu/openlearn/science-maths-technology/cell-signalling/content-section-0#

4.2.a (v) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations

Only the fifth part of this learning objective is included here: describe and explain the processes of endocytosis and exocytosis

Learners refer to the list of substances that enter/leave cells (4.1.b) o State that there is also ‘unwanted’ entry of, e.g. bacteria. o Discuss how the nature of the substance and its size will direct which

Online http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/

http://www.biologymad.com/cells/cellmembrane.htm

http://www.biologymad.com/cells/cellmembrane.htm

http://www.ncbi.nlm.nih.gov/books/NBK9847/


http://www.open.edu/openlearn/science-maths-technology/cell-signalling/content-section-0



http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/




V3.1 37


involving water potential will be set) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set) Key concepts Cells as the units of life, Biochemical processes

mechanism of transport across the membrane is used. o Learners place each item on the list into the correct group: through the

phospholipid bilayer; through membrane proteins; neither (too large/bulk transport). (W) (I) (Challenging)

Learners recall membrane fluidity and read about bulk transport across membranes. (I) (Challenging) o Explain pinocytosis and phagocytosis (see 11.1.a in Unit 5) as forms of

endocytosis. o Learners draw diagrams showing the sequence of events involved in

endocytosis and exocytosis (revise Golgi vesicle formation). o Point out that endocytosis and exocytosis are active (energy-requiring)

mechanisms of movement of substances across membranes.

Textbooks/Publications Biological Nomenclature. Explains

the terminology that should be used when teaching osmosis.

Bio Factsheet 54: Water potential Bio Factsheet 116: Transport

Mechanisms in cells Past Papers Paper 21, Nov 2011, Q1 (b) Paper 22, June 2012, Q1

4.2.c calculate surface areas and volumes of simple shapes (e.g. cubes) to illustrate the principle that surface area to volume ratios decrease with increasing size Key concepts Observation and experiment

Learners use cubes to build 'organisms' of the same shape, with different numbers of blocks, and calculate surface area to volume ratios. (I) (Basic) o Discuss the discovery that SA:V decreases as size of organism (same

shape) increases. o Highlight the relative distances from the outside to the inside.

Note

This serves as an introductory exercise before considering diffusion (4.2.a (i)).

Textbooks/Publications Bio Factsheet 165: Surface Area and

Volume.

4.2.a (i) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set)

Only the first part of this learning objective is included here: describe and explain the processes of diffusion Explain that diffusion is a passive (thermodynamic) method of movement

across membranes. (W) (Basic)

Learners write a definition, make bullet-pointed notes to expand and draw simple diagrams. (I) (Basic)

Online http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/ Textbooks/Publications Bio Factsheet 116: Transport

Mechanisms in cells





V3.1 38


Key concepts Cells as the units of life, Biochemical processes

4.2.d investigate the effect of changing surface area to volume ratio on diffusion using agar blocks of different sizes Key concepts Observation and experiment

Practical: to represent ‘cubic’ organisms, learners cut different-sized agar (technical agar better) or gelatine blocks, coloured using a pH indicator (e.g. cresol red or phenolphthalein), then lower them carefully into dilute hydrochloric acid. Learners time how long it takes for the cube to change colour to measure the effect of surface area to volume ratio on diffusion. (P) (Basic)

Learners note the implications of a changing SA:V on the needs of multicellular plants and animals (size too great; distances too far; diffusion too slow) and the need for transport systems. (I) (Basic)

Discuss shapes that give a large surface area for the same volume (e.g. cube, flattened to give a leaf lamina, with branching to give a plant shape). (W) (Basic) o Explain how this means that in plants diffusion alone is sufficient for

gases, so no transport system is required (presence of stomata and lenticels mentioned). (W) (Challenging)

Online http://teachers.net/lessons/posts/2518.html http://www.neiljohan.com/projects/biology/sa-vol.htm

4.2.b investigate simple diffusion using plant tissue and non-living materials, such as glucose solutions, Visking tubing and agar Key concepts Cells as the units of life

Practical: learners add glucose solution and/or starch suspension to lengths of Visking tubing tied at one end, tie at the other end and place in water (and vice versa) for a set time. The appearance of the tubing and the results of biochemical tests on the internal and external solutions is recorded and results explained. (P) (I) (Basic) (Challenging)

Practical: in agar (in Petri dishes) containing starch, learners cut out a central well, add amylase solution (or use a soaked filter paper disc) and after incubation observe the changes that occur when iodine (in potassium iodide) solution is added. (I) (Basic)

Past Papers Paper 35, Nov 2011, Q1

4.2.a (ii) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations

Only the second part of this learning objective is included here: describe and explain the processes of facilitated diffusion Emphasise that facilitated diffusion is also a passive method of movement

across membranes and that it is diffusion through a channel or carrier protein. Learners make notes and use textbooks/internet. (W) (Challenging)

Online http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/

http://teachers.net/lessons/posts/2518.html

http://teachers.net/lessons/posts/2518.html

http://www.neiljohan.com/projects/biology/sa-vol.htm

http://www.neiljohan.com/projects/biology/sa-vol.htm





V3.1 39


involving water potential will be set) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set) Key concepts Cells as the units of life, Biochemical processes

Textbooks/Publications Bio Factsheet 54: Water potential. Bio Factsheet 116: Transport

Mechanisms in cells Past Papers Paper 22, June 2012, Q1

4.2.a (iii) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set) Key concepts Cells as the units of life, Biochemical processes

Only the third part of this learning objective is included here: describe and explain the processes of osmosis (no calculations involving water potential will be set)

Remind learners that movement of water molecules by crossing the bilayer or via aquaporins is passive. (W) (Basic)

Explain water potential. (W) (Challenging)

Learners define osmosis, make bullet-point notes and draw simple diagrams. (I) (Basic)

Learners write a paragraph stating the similarities and differences between osmosis and (passive) diffusion. (F)

Note

Terminology to use: partially permeable; water potential; solute potential; pressure potential. Learners should ignore other terms that they come across such as hypotonic and hypertonic, osmotic potential, etc.

Online http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/ Textbooks/Publications Biological Nomenclature. Explains

the terminology that should be used when teaching osmosis.

Bio Factsheet 54: Water potential. Bio Factsheet 116: Transport

Mechanisms in cells Past Papers Paper 22, June 2012, Q1

4.2.f explain the movement of water between cells and solutions with different water potentials and explain the different effects on plant and animal cells Key concepts

Recall the different permeabilities of the cell surface membrane, partially permeable and cell wall, (freely- or fully-) permeable. (W) (Basic)

Discuss the terms that can be used to describe cells: plasmolysis / plasmolysed, flaccid, turgid / turgidity and lysis / haemolysis.

Learners describe what happens when animal and plant cells are placed into different external solutions at the same, lower and higher water potential than that of the cells. Diagrams drawn and explanation given in terms of osmosis and water potential.

Practical booklet 3 Online http://www.kscience.co.uk/animations/plasmolysis.htm http://www.biotopics.co.uk/life/osmdia.html http://www.s-cool.co.uk/a-




http://www.kscience.co.uk/animations/plasmolysis.htm

http://www.kscience.co.uk/animations/plasmolysis.htm

http://www.biotopics.co.uk/life/osmdia.html

http://www.biotopics.co.uk/life/osmdia.html

http://www.s-cool.co.uk/a-level/biology/cells-and-organelles/revise-it/movement


V3.1 40


Cells as the units of life, Observation and experiment

Learners complete a worksheet (prepared by you) with the cellular environment and the external solutions identified only with values of water potential. (I) (Basic) (Challenging)

Practical: learners use water and different concentrations of salt solutions to observe onion cells and make high power drawings. (I) (Challenging)

Extension practical: as above, learners observe changes in red blood cells (use a safe, acceptable source). Making estimates of cell numbers makes this a semi-quantitative investigation. (I) (Challenging)

level/biology/cells-and-organelles/revise-it/movement http://www.biologymad.com/resources/ch%202%20-%20getting%20in%20and%20out%20of%20cells.pdf Past papers Paper 52, June 2011, Q1

4.2.e investigate the effects of immersing plant tissues in solutions of different water potential, using the results to estimate the water potential of the tissues Key concepts Cells as the units of life, Observation and experiment

Learners immerse pieces of root or stem (e.g. potato tuber tissue) in sucrose solutions of different concentrations. The water potential of the solution in which there is no change in length or mass is the estimate of water potential of the tissue. (I) (Basic)

Practical booklet 3 develops skills for Paper 3 (see Teacher’s practical notes), followed up by Q1 in Paper 52, June 2011 (data interpretation).

Practical booklet 3 Online http://www.biotopics.co.uk/life/carrot.html#top http://www.saps.org.uk/secondary/teaching-resources/286-measuring-the-water-potential-of-a-potato-cell Textbooks/Publications King p.60-63 Siddiqui p.38, 40-43. Past papers Paper 52, June 2011, Q1

4.2.a (iv) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport,

Only the fourth part of this learning objective is included here: describe and explain the processes of active transport Discuss examples of active transport to show why it is necessary to transport

substances against the concentration gradient. (W) (Basic)

Learners make notes on active transport, including the role of membrane (carrier) proteins. (I) (Basic)

Learners write a paragraph stating the similarities and differences between facilitated diffusion and active transport. (I) (Challenging)

Learners construct a summary chart with main points (see below), and then

Online http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/ Textbooks/Publications Bio Factsheet 116: Transport

Mechanisms in cells



http://www.biologymad.com/resources/ch%202%20-%20getting%20in%20and%20out%20of%20cells.pdf




http://www.biotopics.co.uk/life/carrot.html#top

http://www.biotopics.co.uk/life/carrot.html#top

http://www.saps.org.uk/secondary/teaching-resources/286-measuring-the-water-potential-of-a-potato-cell







V3.1 41


endocytosis and exocytosis (no calculations involving water potential will be set) Key concepts Cells as the units of life, Biochemical processes

add details. (H) (F) (Challenging)

Past Papers Paper 22, June 2012, Q1

transport mechanism

passive active

passive

diffusion

facilitated

diffusion

bulk

transport

active

transport

endocytosis exocytosis

phagocytosis pinocytosis


V3.1 42

Unit 3: DNA and the mitotic cell cycle


Learners should have covered cell structure in Unit 2. Building on the key concept of cells as the basic unit of life, they should be familiar with the terms unicellular and multicellular and know the definition of a tissue. Knowledge of the cell structures involved in protein synthesis and in mitotic cell division is essential so that learners understand where and when the biological processes described in this unit occur. The role of enzymes in biological processes should be appreciated. Context

This unit brings together important ideas from Units 1 and 2. Eukaryotic cells can divide by mitosis and meiosis. Cells arising as a result of mitosis are genetically identical to each other and their parent cell, owing to faithful DNA replication during the cell cycle. DNA transcription and translation occurs during the cell cycle and results in protein synthesis. Learners will have studied the structure of nucleic acids and proteins and will know the cell structures involved in protein synthesis. DNA as the molecule of heredity, a key concept, contains coded information for the synthesis of proteins. The central dogma describes the flow of genetic information in a cell and is a concept that works at a molecular level to help explain the more general statement that “the nucleus controls the cell’s activities”. Mitotic division by stem cells allows multicellular organisms to develop and to maintain their programmed structure and organisation. Malfunctioning of cells may cause uncontrolled growth and division and lead to tumours, or could cause the early death of cells. An understanding of the processes involved in the cell cycle will underpin later studies of genetic control and detailed knowledge of mitotic division will facilitate understanding of the events occurring in meiotic division, studied later in the scheme of work. Outline

This unit covers the mitotic cell cycle and begins with detail of the structure of chromosomes. After gaining an overview of the cell cycle, DNA replication by the semi-conservative mechanism is tackled as part of late interphase of the cell cycle and then consideration is given to the importance of mitosis to unicellular and multicellular organisms. Stem cells are introduced and an explanation of how uncontrolled division can lead to tumours is given. To aid understanding of the events occurring during mitosis, especially of chromosome behaviour, learners also have the opportunity to study cells in stages of mitosis in prepared or temporary slides. The unit finishes with a molecular definition of a gene and a gene mutation, and provides detail of DNA transcription and translation, which gives learners further insight into processes occurring during interphase of the mitotic cell cycle. Teaching time



V3.1 43


5.1.a describe the structure of a chromosome, limited to DNA, histone proteins, chromatids, centromere and telomeres Key concepts Biochemical processes, DNA, the molecule of heredity

State that the structure of chromatin alters during the cell cycle and explain that in a non-dividing cell, chromatin is in its least condensed state. (W) (Basic) o Learners describe a chromosome in a non-dividing cell or a cell in

interphase as a molecule of DNA complexed with histone protein. o Remind/explain that the length of DNA in a chromosome is organised into

functional units, genes.

Learners draw and annotate a chromosome at prophase/metaphase to include two sister chromatids, the centromere and telomeres o Learners write a paragraph to explain that an identical sister chromatid is

formed before cell division. (W) (I) (Basic)

Extension: learners find out more about euchromatin and heterochromatin. (I) (Challenging)

Online http://www.dnalc.org/resources/3d/07-how-dna-is-packaged-basic.html http://ghr.nlm.nih.gov/handbook/basics/chromosome

5.1.c outline the cell cycle, including interphase (growth and DNA replication), mitosis and cytokinesis Key concepts Cells as the units of life, DNA, the molecule of heredity

Explain that only some cells carry out mitotic cell division (most remain in the interphase state) and one mitotic cell cycle results in two cells, following a nuclear division (mitosis) and a cell division. (W) (Basic)

Learners research and produce an outline, annotated diagram of a cell cycle. (I) (Challenging) o Include the two main phases, interphase and a mitotic phase and note that

the timing of cell division is controlled by a number of genes. o Indicate that DNA replication takes place in late interphase and that protein

synthesis occurs throughout interphase. o Indicate that cell growth occurs in interphase. o Include for the mitotic phase (mitosis) the main stages: prophase,

metaphase, anaphase, telophase and also indicate cytokinesis following telophase.

Add background information, e.g. cytokinesis only takes place if new cells are to be formed (without cytokinesis a multinucleate cell is formed); notes on the G1, S and G2 phases (use a key to indicate background information only).

Learners label incomplete diagrams (prepared by you). (F)

Introduce and give a general outline of stem cells (for 5.1.e), explaining that they divide to become more stem cells and cells that differentiate. o Discuss the location of stem cells in the bone marrow and within epithelial

tissue (describe this as lining or surface tissue).

Online http://www.cellsalive.com/cell_cycle.htm Past Papers Paper 22, June 2011, Q1 Paper 23, June 2011, Q1 (c)

http://www.dnalc.org/resources/3d/07-how-dna-is-packaged-basic.html

http://www.dnalc.org/resources/3d/07-how-dna-is-packaged-basic.html

http://ghr.nlm.nih.gov/handbook/basics/chromosome

http://ghr.nlm.nih.gov/handbook/basics/chromosome

http://www.cellsalive.com/cell_cycle.htm

http://www.cellsalive.com/cell_cycle.htm


V3.1 44


o For plants, use the terms ‘meristem’, ‘meristematic’ and ‘cambium’ and discuss locations within plants where this tissue occurs. (W) (Basic)

6.1.c describe the semi-conservative replication of DNA during interphase Key concepts Biochemical processes, DNA, the molecule of heredity

Revise 5.1.a and 5.1.c so learners understand the need for interphase chromosomes (and hence DNA) to replicate before mitosis occurs. (W) (Basic)

Learners match events/descriptions (printed on strips of card) to unlabelled diagrams of semi-conservative replication to correctly describe the sequence of events that occur in the process (you’ll need to prepare this in advance). (P) (I) (Challenging) o Ensure learners are clear about the role of DNA polymerase and DNA

ligase and the concept of activated nucleotides. o Include a description pointing out that replication occurs in opposite

directions for each strand.

Learners explain what is meant by (define) semi-conservative replication. (I) (Basic)

Learners use their cut-outs of DNA nucleotides to simulate DNA replication. o Use very short sections of double strands, separate them to show the

template strands and build up the two complementary strands. (P) (I) (Basic)

o Extension: simulate as it occurs – one strand built-up in one direction as a continuous process and the other in Okazaki fragments (not required knowledge). (P) (I) (Challenging)

Discuss how this process allows for faithful replication to produce identical DNA molecules and hence genetically identical sister chromatids, ready for mitotic cell division. (W) (Basic)

Note

The Meselsohn and Stahl investigation is not required learning but learners could be given the information to test application of knowledge and understanding.

The poster (from Unit 1, DNA as the ideal molecule of inheritance) should remain visible as this unit is covered.

Online http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html http://highered.mcgraw-hill.com/sites/dl/free/0072437316/120076/bio23.swf Textbooks/Publications Bio Factsheet 207: How science

works: Meselson and Stahl’s classic experiment.

Past Papers Paper 22, Nov 2011, Q4 (c)(d) Paper 23, Nov 2011, Q5 (b)

5.1.d outline the significance of telomeres

Explain that DNA replication results in loss of a short section of the ends of the chromosome and that telomeres are made from repeating sequences of

Online http://learn.genetics.utah.edu/conte

http://www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html



http://highered.mcgraw-hill.com/sites/dl/free/0072437316/120076/bio23.swf



http://learn.genetics.utah.edu/content/chromosomes/telomeres/


V3.1 45


in permitting continued replication and preventing the loss of genes Key concepts DNA, the molecule of heredity

nucleotides. (W) (Basic)

Learners suggest how telomeres are useful, with a follow-up outline of their role discussed and notes made: (W) (I) (Challenging) o Telomeres serve to prevent the ends of chromosomes from being

degraded. o Without telomeres the ends would appear damaged to the cell’s repair

machinery so they prevent the ends from being joined to the ends of other chromosomes.

o Telomeres protect genes and the integrity of the genetic material and allow continued replication.

Extension: learners investigate the shortening of telomeres with age and the role of telomerase. (I) (Challenging)

nt/chromosomes/telomeres/

5.1.b explain the importance of mitosis in the production of genetically identical cells, growth, cell replacement, repair of tissues and asexual reproduction Key concepts Cells as the units of life, DNA, the molecule of heredity

Ensure that learners know the definition of a tissue. (W) (Basic)

Discuss with learners how their own growth occurs and how damaged tissue is repaired. Remind them that replacement of cells can occur when cells are old/die thorough programmed cell death.

Refer to the poster (DNA as the ideal molecule of inheritance) and agree that it is essential that each daughter cell contains the same complete set of instructions and the same number of chromosomes as the parent (i.e. genetically identical). (W) (Basic)

Discuss how cells could be rejected (attack by the immune system) if the daughter cells were genetically different and not recognised as ‘self’ (link to antigens in Unit 2 and see Unit 5). (W) (Challenging)

Learners investigate simple examples where mitosis is involved in reproduction e.g. Hydra, or a plant that reproduces asexually. (H) (Basic)

Discuss briefly the terms clone and vegetative propagation. (W) (Basic)

Learners make brief notes summarising the discussions. (H) (F)

Online http://www.nature.com/scitable/topicpage/replication-and-distribution-of-dna-during-mitosis-6524841 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC256985/pdf/03-10-043_p214.pdf http://sciencecases.lib.buffalo.edu/cs/collection/ Past Papers Paper 23, June 2011, Q1 (b)

5.1.e outline the significance of mitosis in cell replacement and tissue repair by stem cells and state that uncontrolled cell division can result in the formation of a tumour

Learners research examples, e.g. the repair of damage to intestinal epithelial cells, replacement of old cells in the gas exchange system. (I) (Basic) o Extend learning to discuss how cells that are structurally and functionally

the same need to be genetically identical. (W) (Basic) o Remind learners that all cells in the body have the same set of instructions

and explain that control of cell function is by the organised ‘switching on’ of

Online http://stemcells.nih.gov/info/basics/pages/basics4.aspx http://www.medicalnewstoday.com/info/stem_cell/

http://learn.genetics.utah.edu/content/chromosomes/telomeres/

http://www.nature.com/scitable/topicpage/replication-and-distribution-of-dna-during-mitosis-6524841



http://www.ncbi.nlm.nih.gov/pmc/articles/PMC256985/pdf/03-10-043_p214.pdf



http://sciencecases.lib.buffalo.edu/cs/collection/

http://sciencecases.lib.buffalo.edu/cs/collection/

http://stemcells.nih.gov/info/basics/pages/basics4.aspx

http://stemcells.nih.gov/info/basics/pages/basics4.aspx

http://www.medicalnewstoday.com/info/stem_cell/

http://www.medicalnewstoday.com/info/stem_cell/


V3.1 46


Key concepts Cells as the units of life, DNA, the molecule of heredity

relevant genes. (W) (Challenging)

Explain (see 5.1.c) that the timing of cell division is under genetic control; an alteration in a gene could lead to the cell dividing uncontrollably to form a tumour – an example of how a cell malfunctioning upsets the delicate balance. (W) (Challenging)

Learners sequence a set of diagrams (prepared by you) showing changes that occur to result in a tumour (should include an abnormal mass from which two arrows emerge to a benign growth and a cancerous (malignant) growth (see Unit 5). (I) (Basic). o Following research, learners add brief annotations to the diagrams. (H)

(Challenging) o Extension: learners research differences between the two types of tumour.

(I) (Challenging)

Extend 5.1.c to discuss the statement: "Stem cells allow multicellular organisms to develop and to maintain their programmed structure and organisation”. (W) (G) (Challenging)

Extension: learners investigate biotechnological applications, e.g. the use of adult stem cells in research and therapy. (I) (Challenging)

Past Papers Paper 21, Nov 2011, Q4 (b)

5.2.a describe, with the aid of photomicrographs and diagrams, the behaviour of chromosomes in plant and animal cells during the mitotic cell cycle and the associated behaviour of the nuclear envelope, cell surface membrane and the spindle (names of the main stages of mitosis are expected) Key concepts Cells as the units of life, DNA, the molecule of heredity

Demonstrate using a model of a cell (2n=4) (2 short and 2 long pipe cleaners = chromosomes; cell surface membrane and nuclear envelope = string). (W) (Basic) o Model the events as a continuous process. o Model replication by attaching a second pipe cleaner to the first. Simulate

nuclear envelope disassembly by cutting the string into smaller lengths. o Cytokinesis should be described for both animal and plant cells. o Learners describe and make suggestions as to why various events occur.

(W) (Basic) (Challenging)

From a list (prepared by you), learners match an event that occurs in relation to the spindle fibres and spindle (centrioles in animal cells only) to the behaviour of the chromosomes during the mitotic cell cycle. (W) (Basic)

Learners work with their own models and talk through each stage. (P) (Challenging)

Learners make annotated diagrams of stages in mitosis. (I) (Challenging)

Learners practise identification of the stages and description of events using a

CD-ROM Bioscope – has material which

covers this Online http://faculty.nl.edu/jste/mitosis.htm http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/main.html http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html Textbooks/Publications Bio Factsheet 76: The eukaryotic

cell cycle and mitosis

http://faculty.nl.edu/jste/mitosis.htm

http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/main.html

http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/main.html

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html





V3.1 47


range of photomicrographs and diagrams of both plant and animal cells. (I) (Basic) (Challenging)

Learners sequence images of a cell at various stages during the cycle, naming the stages and noting chromosome behaviour. (F)

Note

Condensation/coiling of DNA to form the prophase chromosome can be simulated by taking a very long piece of thin wire that is then wrapped round a pencil (which is removed) to make a coiled, string-like structure that is now much shorter, fatter and more visible.

Past Papers Paper 21, June 2011, Q1 (c) Paper 23, June 2011, Q1 (a) Paper 21, Nov 2011, Q4 (c)

5.2.b observe and draw the mitotic stages visible in temporary root tip squash preparations and in prepared slides of root tips of species such as those of Vicia faba and Allium cepa Key concepts Cells as the units of life

Learners draw from a prepared slide a plan diagram of a root tip to indicate: the root cap; meristematic area (zone of cell division); zone of elongation (expansion); and zone of differentiation. (I) (Basic)

Learners identify, draw and annotate cells (high power) in all stages of mitosis. (I) (Challenging)

Learners prepare a root tip squash (e.g. garlic or onion root tips with acetic orcein or toluidine blue) and examine their slide and those of others for stages of mitosis. (G) (I) (Basic)

Learners use the eyepiece graticule by measuring the relative length and width of chromosomes and cells. (I) (Challenging) o Learners use the calibrated eyepiece graticule to measure the size of

chromosomes in m. (I) (Challenging)

Extension: learners investigate why each step of the procedure in the root tip squash preparation is necessary. (I) (Challenging)

Online http://www.microscopy-uk.org.uk/micropolitan/index.html http://www.saps.org.uk/secondary/teaching-resources/552-floating-garlic-growing-roots- http://www.saps.org.uk/secondary/teaching-resources/288-investigating-mitosis-in-allium-root-tip-squash Textbooks/Publications King p.236, 207, 209 Siddiqui p.79-81.

6.2.a state that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms part of a DNA molecule Key concepts Biochemical processes, DNA, the molecule of heredity

Learners recall primary structure and a polypeptide (Unit 1) and suggest a definition of a gene from previous learning objectives. o Refer to the ‘DNA as the ideal molecule’ poster and ensure learners

understand the idea of the term ‘coded’ (see 6.2.c, 6.2.d). (W) (Basic) o Discuss the fact that the sequence of nucleotides comprising a gene codes

for the amino acid sequence in a polypeptide chain. (W) (Basic)

Background discussion/extension research about the human genome project. (W) (I) (Basic) (Challenging)

Note

Online http://evolutionlist.blogspot.co.uk/2006/10/new-definitions-of-gene.html http://www.sanger.ac.uk/ http://www.yourgenome.org/

http://www.microscopy-uk.org.uk/micropolitan/index.html

http://www.microscopy-uk.org.uk/micropolitan/index.html

http://www.saps.org.uk/secondary/teaching-resources/552-floating-garlic-growing-roots-



http://www.saps.org.uk/secondary/teaching-resources/288-investigating-mitosis-in-allium-root-tip-squash




http://evolutionlist.blogspot.co.uk/2006/10/new-definitions-of-gene.html

http://evolutionlist.blogspot.co.uk/2006/10/new-definitions-of-gene.html

http://www.sanger.ac.uk/

http://www.yourgenome.org/


V3.1 48


If learners query the origin of RNA, explain that there are genes that code for tRNAs and rRNAs and that mRNA is an intermediate molecule in producing the polypeptide. (W) (Basic).

For A Level, learners should understand that these proteins, including enzymes, will ultimately allow development and control of cells and hence organisms (i.e. they determine the nature of organisms).

6.2.b state that a gene mutation is a change in the sequence of nucleotides that may result in an altered polypeptide Key concepts Biochemical processes, DNA, the molecule of heredity, Natural selection

After learners write this definition, use question and answer to recall (from Unit 1) that primary structure determines secondary and tertiary structure, which then determine the shape and shape of, e.g. active site, specific channel, receptor site. This determines the function of the protein. (W) (Basic)

Stress to learners that the gene is responsible for a particular feature, trait or characteristic and that a mutation is just an alternative form of the gene, an allele. (W) (Basic)

Note

Online resources may be best understood after learning about the genetic code and transcription and translation

Learners do not need to define an allele at this point, see 16.2.a.

Online http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/genemutation http://www.yourgenome.org/dgg/general/var/var_3.shtml

6.2.c describe the way in which the nucleotide sequence codes for the amino acid sequence in a polypeptide with reference to the nucleotide sequence for Hb

A (normal)

and HbS (sickle cell) alleles of the

gene for the -globin polypeptide Key concepts Cells as the units of life, Biochemical processes, DNA, the molecule of heredity, Natural selection

Learners write out definitions of a gene and a gene mutation. (F)

Learners suggest why DNA needs to remain in the nucleus (large size, less prone to degradation). o Lead the discussion to explain that a ‘messenger’ molecule needs to be

formed, in transcription, to take the information to the ribosomes. (W) (Basic)

Discuss the concepts involved in the central dogma (http://en.wikipedia.org/wiki/Central_dogma_of_molecular_biology overlap with ideas in 6.2.d). (W) (Basic) o Learners produce an annotated flow chart representing the flow of

information, beginning with DNA and ending in a functioning protein. o Learners identify the point at which the nucleotide sequence becomes an

amino acid sequence. o State that the process is termed translation (details in 6.2.d).

Learners study a DNA genetic dictionary/ DNA triplet table to work out, from

Online http://www.yourgenome.org/dgg/general/proteins/proteins_2.shtml http://www.kumc.edu/gec/ http://www.youtube.com/watch?v=J3HVVi2k2No Past Papers Paper 23, June 2011, Q2 (b)(c) Paper 21, Nov 2011, Q3 (b) Paper 21, Nov 2013, Q5

http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/genemutation

http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/genemutation

http://www.yourgenome.org/dgg/general/var/var_3.shtml

http://www.yourgenome.org/dgg/general/var/var_3.shtml

http://en.wikipedia.org/wiki/Central_dogma_of_molecular_biology

http://www.yourgenome.org/dgg/general/proteins/proteins_2.shtml

http://www.yourgenome.org/dgg/general/proteins/proteins_2.shtml

http://www.kumc.edu/gec/

http://www.youtube.com/watch?v=J3HVVi2k2No

http://www.youtube.com/watch?v=J3HVVi2k2No


V3.1 49


specific nucleotide base sequences, specific amino acid sequences. (P) (I) (Basic) (Challenging) o Explain this is the sequence on the strand (the template strand) that is used

to produce the polypeptide o Include the sections where the nucleotide sequences of normal and sickle-

cell alleles differ.

Note

Learners should also be able to use the sequence on the non-template strand to work out the amino acid sequence (using the DNA triplet table)

The sickle cell -globin polypeptide and sickle cell anaemia also occur in Units 5 and 7.

It is a common error for learners to state that DNA is a chain of amino acids. When learners guess or are given incorrect matches, many will learn the incorrect match, so only reinforce the correct relationship between nucleotides and DNA / RNA, and between amino acids and protein.

6.2.d describe how the information in DNA is used during transcription and translation to construct polypeptides, including the role of messenger RNA (mRNA), transfer RNA (tRNA) and the ribosomes Key concepts Biochemical processes, DNA, the molecule of heredity

Previous learning objectives have included enough additional information to prepare learners for the details of transcription and translation.

Learners sequence a set of events to describe and explain the process of transcription. (P) (I) (Basic) (Challenging) o Ensure learners realise that mRNA transcripts pass out through the nuclear

pores to the ribosomes. (W) (Basic) o Explain post-transcriptional modification: sections not required, introns (now

known to have a role, not ‘genetic junk’ as previously believed), may be cut out of the initial transcript and the ‘meaningful’ sections, exons, re-sealed to give shorter mRNA transcripts. (W) (Challenging)

Formalise knowledge of the genetic code (universal, non-overlapping, degenerate, sequential), by introducing the mRNA genetic dictionary / mRNA codon table.

For translation, provide learners with a set of diagrams (prepared by you) that can be annotated and discussed.

Learners research the different ways the polypeptide formed can be modified in post-translational modification. (I) (Challenging)

Learners write a paragraph on each of mRNA, tRNA and the ribosomes,

Online http://learn.genetics.utah.edu/conte

nt/molecules/transcribe/ http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/protein_synthesis/protein_synthesis.html http://www.pbs.org/wgbh/aso/tryit/dna/ Textbooks/Publications Bio Factsheet 22: Protein synthesis

I – nucleic acids Bio Factsheet 49: Protein synthesis

II – mechanisms Past Papers Paper 21, June 2011, Q3 (c) Paper 23, June 2011, Q2 (d)

http://learn.genetics.utah.edu/content/molecules/transcribe/

http://learn.genetics.utah.edu/content/molecules/transcribe/

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/protein_synthesis/protein_synthesis.html




http://www.pbs.org/wgbh/aso/tryit/dna/

http://www.pbs.org/wgbh/aso/tryit/dna/


V3.1 50


explaining their roles in transcription and translation. (H) (F) (Challenging)

Find the DNA nucleotide sequences of sections of proteins (choose from the syllabus) to produce a worksheet (and mark scheme). o Learners use the genetic code and one or more pieces of information to

work out missing information. Completed worksheets show the tRNA molecules involved and the sequences of template and non-template DNA strands, mRNA and amino acids. (H) (F) (Basic) (Challenging)

o Extension: learners explain why a DNA nucleotide sequence worked out only using an amino acid sequence may not represent the actual DNA. (I) (Challenging)

Learners produce a large annotated diagram to show transcription and translation in relation to the different locations within the cell. (H) (Challenging)

Extension: learners research how post-transcriptional modification (removal of introns and resealing of exons) allows one gene to be able to produce variations of the protein product. (I) (Challenging)

Note

TransCription comes before transLation alphabetically as well as in protein synthesis.

With website animations, check the level of detail before recommending to learners.

Paper 23, Nov 2011, Q5 (c) Paper 22, Nov 2011, Q4 (b) Paper 22, Nov 2011, Q4 (c)(d)


V3.1 51

Unit 4: Transport and gas exchange


Knowledge of cell structure, as covered in Unit 2, will enable learners to apply knowledge to cells involved in transport and gas exchange. An understanding of diffusion, osmosis and active transport from Unit 2 is required, including confidence in understanding the movement of water in terms of differences in water potential. Learners will need to have an understanding of haemoglobin structure and of hydrogen bonding between water molecules from Unit 1. It will be helpful if learners have acquired basic knowledge of the mammalian circulatory system in previous studies. Context

This unit extends the key concept of cells as the units of life by looking at the way in which cells and tissues of plants and mammals, multicellular organisms, are provided with their requirements and how humans, as multicellular organisms, exchange gases in the lungs. The unit builds on learner knowledge of cell structure and movement into and out of cells and highlights the importance of water as a transport medium. The work on blood in this unit leads into the immunity section in Unit 5. Much of this unit lays the foundations for further work on physiology at A Level. In Unit 9, learners will study the way in which oxygen is used by cells for the biochemical process of aerobic respiration, and how carbon dioxide is produced as a result of this process. Outline

The topic of transport in plants is introduced by improving learner knowledge of plant anatomy and histology and their understanding of the relation between the structure and function of transport tissues. Details of transport of water and minerals are covered, including a consideration of the factors affecting the rate of transpiration, which gives learners the opportunity to carry out investigative practical work. Adaptations of organisms to their environment are exemplified by reference to xerophytes. The transport of assimilates by phloem tissue is also covered. The topic of mammalian transport is introduced by considering the meaning of a closed double circulation and then progresses to structure and function of the blood vessels, blood and heart. A comparison of blood, tissue fluid and lymph is made. The carriage of respiratory gases is covered, which includes revisiting the structure and function of haemoglobin from Unit 1. Detail of gas exchange at the alveolus is covered. The gross and fine structure of the human gas exchange system will allow learners to see the link between structure and function. Learners will make comparisons in this unit, for example between xylem and phloem tissue, between an artery and vein, between blood, tissue fluid and lymph, and between the two sides and upper and lower chambers of the heart .There are many good opportunities within this unit for learners to improve their microscope handling, observational and diagram-drawing skills, and to develop manipulative and dissection skills if they choose to dissect a mammalian heart. Teaching time



V3.1 52


7.1.a draw and label from prepared slides plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants using an eyepiece graticule to show tissues in correct proportions (see 1.1.c) Key concepts Cells as the units of life, Observation and experiment

Revise a simple diagram of a plant: leaves and petioles, stem, (soil level), root(s) and piliferous / root hair region. (W) (Basic) o Explain the difference between: tissue and organ; transverse and longitudinal

sections (TS and LS). o Explain what is meant by a herbaceous (i.e. non-woody) dicotyledon.

Discuss tissue distribution in leaves, roots and stem sections by projecting an electronic image onto a screen. (W) (Basic) o Learners see what they should observe later using the microscope (revise

use). o Describe how to draw the image as a plan diagram.

Learners identify tissues (especially the distribution of the vascular tissue) and make plan diagrams (low power) from slides of TS of a leaf, stem or root (dicotyledonous plants e.g. Ranunculus and Ligustrum), using the eyepiece graticule to gauge the correct proportions. (I) (Challenging)

Learners draw labelled diagrams of stem and leaf sections and construct a table comparing the two; similarities run across the columns, differences in separate columns. (I) (Challenging)

Note

Learners should be able to recognise: epidermis, endodermis, mesophyll, xylem, phloem, cambium, cortex, pith.

High quality microscope slides are available to order, including those used in previous practical examinations from the Cambridge publications catalogue www.cie.org.uk/cambridge-for/teachers/order-publications

CD-ROM Bioscope Online University biology department and microscope manufacturer websites, e.g.: http://micro.magnet.fsu.edu/index.html http://images.botany.org Textbooks/Publications Siddiqui p.5-7, 112, 115-124, 135-139 Past Papers Paper 23, June 2011, Q3 Paper 35, June 2011, Q2 Paper 31, June 2011, Q2 Paper 34, June 2011, Q2 Paper 33, June 2013, Q2

7.1.b draw and label from prepared slides the cells in the different tissues in roots, stems and leaves of herbaceous dicotyledonous plants using transverse and longitudinal sections Key concepts Cells as the units of life, Observation and experiment

Learners observe slides showing LS. An eyepiece graticule and stage micrometer can be used for measurement. (I) (Challenging)

Learners draw and label individual cells under high power (from TS and LS slides). (I) (Challenging)

Extension: learners practise using the eyepiece graticule and stage micrometer to estimate actual dimensions of the cells. (I) (Challenging)

Background: discuss briefly differences between monocotyledons and dicotyledons. (W) (Basic)

An extension discussion: outlining the anatomical transition in the area where the root becomes the stem.

CD-ROM Bioscope – Superb slides and learning tasks, including chloroplasts in Elodea, a variety of leaf sections, including sun and shade leaves. Online University biology department and microscope manufacturer websites, e.g.


http://micro.magnet.fsu.edu/index.html


http://images.botany.org/


V3.1 53


Note

High quality microscope slides are available to order, including those used in previous practical examinations from the Cambridge publications catalogue www.cie.org.uk/cambridge-for/teachers/order-publications

http://www.vcbio.science.ru.nl/en/virtuallessons/leaf/ http://www.mhhe.com/biosci/pae/botany/histology/html/ptmodov.htm http://leavingbio.net/FLOWERING%20PLANTS.htm http://images.botany.org/ Textbooks/Publications Siddiqui p.5-7, 112, 115-124, 135-139 Bio Factsheet 19: Plant tissues Past Papers Paper 23, Nov 2011, Q3 (a)

7.1.c draw and label from prepared slides the structure of xylem vessel elements, phloem sieve tube elements and companion cells and be able to recognise these using the light microscope Key concepts Cells as the units of life, Observation and experiment

Use photomicrographs and diagrams to illustrate and discuss, with teacher prompts, the structure of xylem vessel elements, phloem sieve tube elements and companion cells. (G) (I) (Challenging)

Learners add annotations to labelled diagrams of these three cell types. (F)

CD-ROM Bioscope – useful for this section. Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PlantTissues.html http://leavingbio.net/FLOWERING%20PLANTS.htm http://www.mhhe.com/biosci/pae/botany/histology/html/ptmodov.htm Textbooks/Publications Siddiqui p.5-7, 112, 115-124, 135-139 Bio Factsheet 19: Plant tissues Bio Factsheet 146: Tracheids, vessels and sieve tubes


http://www.vcbio.science.ru.nl/en/virtuallessons/leaf/

http://www.vcbio.science.ru.nl/en/virtuallessons/leaf/

http://www.mhhe.com/biosci/pae/botany/histology/html/ptmodov.htm



http://leavingbio.net/FLOWERING%20PLANTS.htm


http://images.botany.org/

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PlantTissues.html









V3.1 54


Bio Factsheet 132: Phloem

7.2.a explain the movement of water between plant cells, and between them and their environment, in terms of water potential (see 4.2. No calculations involving water potential will be set) Key concepts Cells as the units of life, Organisms in their environment

Provide learners with an overview diagram of the movement of water down a water potential gradient from soil to air. (W) (Basic) o Learners add given numerical values of water potential to the different

locations, for comparison, and annotate the diagram. (I) (Challenging)

Learners recall osmosis and the concept of water potential. o Learners complete a worksheet (prepared by you) containing examples of

adjacent cells / cells and their environment with water potential values. Learners work out and explain which way water will flow. (H) (F) (Basic) (Challenging)

Online http://www.biologymad.com/resources/transpiration.swf Textbooks/Publications Bio Factsheet 225: Synoptic biology: water potential.

7.2.c describe the pathways and explain the mechanisms by which water and mineral ions are transported from soil to xylem and from roots to leaves (include reference to the symplastic pathway and apoplastic pathway and Casparian strip) Key concepts Cells as the units of life, Biochemical processes

From a diagram, learners suggest how a root hair cell is adapted for water and mineral ion uptake (e.g. large surface area, lack of cuticle, thin cell walls, membrane transport proteins, mitochondria). (W) (G) (Challenging)

Learners suggest how mineral ions are taken up by the root hair cell. (W) (Basic)

Learners research the most important mineral ions that are required, giving reasons. (H)

Ensure that learners know the difference between the apoplastic pathway and symplastic pathway (include the vacuolar pathway). o Agree that osmosis is not involved in the apoplast pathway (no membranes). o Use a model to explain why water has to take a symplastic pathway at the

endodermis (suberised Casparian strip). o Learners use arrows and labels to show the different pathways on diagrams

and annotate, using the terms water potential and water potential gradient. (W) (I) (Basic) (Challenging)

Learners stand small plants (intact root systems, soil washed off) in dye (e.g. eosin) for 10-30 minutes, then cut thin sections to investigate the distribution of the dye and show the position and continuous nature of xylem vessels (the dye collects in the leaf as water is lost by transpiration). (I) (Challenging)

Learners use cut petioles of variegated leaves to make sections and observe xylem tissue. (P) (I) (Basic)

Discuss briefly the concept of root pressure (outline only). (W) (Basic)

Online http://www.microscopy-uk.org.uk/mag/artmar00/watermvt.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/X/Xylem.html http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::600::480::/sites/dl/free/007353224x/788092/Water_Uptake.swf::Water%20Uptake Textbooks/Publications Bio Factsheet 82: Transport in flowering plants Bio Factsheet 108: Water movement across the root Past Papers Paper 23, June 2011, Q3 (a)

http://www.biologymad.com/resources/transpiration.swf

http://www.biologymad.com/resources/transpiration.swf

http://www.microscopy-uk.org.uk/mag/artmar00/watermvt.html



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/X/Xylem.html


http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::600::480::/sites/dl/free/007353224x/788092/Water_Uptake.swf::Water%20Uptake






V3.1 55


Note

Root hairs can be seen clearly on newly-germinated seedlings, such as mung beans, if these are grown on damp filter paper or cotton wool.

Do not discuss the concept of capillarity.

Learners are better to explain water movement in terms of water potential gradients to avoid confusion with mass flow in phloem.

7.2.b explain how hydrogen bonding of water molecules is involved with movement in the xylem by cohesion-tension in transpiration pull and adhesion to cellulose cell walls Key concepts Biochemical processes

Tackle cohesion-tension first: use a question and answer session to help learners make the link between hydrogen bonding of water molecules (cohesive forces) and the concept of transpiration pull. (W) (Basic)

Discuss the concept of adhesion. Remind learners that the attraction of water molecules to the secondary cell wall of xylem vessel elements is mainly as a result of hydrophilic cellulose (which is impregnated with lignin). (W) (Basic)

Learners write a paragraph explaining the difference between cohesion and adhesion in the movement of water up the xylem. (F)

Learners research what is meant by a transpiration stream. (H) (Basic)

Online http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Intermolecular_Forces/Cohesive_And_Adhesive_Forces http://www.microscopy-uk.org.uk/mag/artmar00/watermvt.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/X/Xylem.html. http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::600::480::/sites/dl/free/007353224x/788092/Water_Uptake.swf::Water%20Uptake Textbooks/Publications Bio Factsheet 82: Transport in flowering plants Bio Factsheet 108: Water movement across the root Past Papers Paper 23, June 2011, Q3 (a)

http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Intermolecular_Forces/Cohesive_And_Adhesive_Forces

















V3.1 56


7.2.d define the term transpiration and explain that it is an inevitable consequence of gas exchange in plants Key concepts Cells as the units of life

Learners write a definition of transpiration. (I) (Basic)

Learners draw a large diagram of a vertical section through part of a leaf, adding numbered annotations to show the pathway of water (beginning with water leaving xylem vessels) and the sequence of events occurring, using correct water potential terminology. (I) (Challenging) o Emphasise the need to refer to water evaporated from the moist cell walls of

the spongy mesophyll cells as water vapour.

Discuss the association between transpiration (reduces the water potential at the top of the plant) and tension (of cohesion-tension). (W) (Basic)

Learners explain the differences between transpiration and evaporation. (F)

Discuss cuticular transpiration (links to 7.2.f, leaves of xerophytes). (W) (Basic)

Learners study a graph showing how the rate of transpiration varies during a 24-hour day and interpret using a word list (stomata, open, closed, photosynthesis, oxygen, carbon dioxide, gas exchange, transpiration). (I) (Basic)

Extension: take climate into account and interpret a graph (prepared by you) with transpiration varying over a few days. (I) (Challenging)

Learners research the advantages of transpiration and produce a list. (H) (Basic)

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transpiration.html Textbooks/Publications Bio Factsheet 64: Transpiration Bio Factsheet 81: Gas exchange in plants Past Papers Paper 23, Nov 2011, Q3 (b) Paper 22, Nov 2013, Q3 (a)

7.2.e investigate experimentally and explain the factors that affect transpiration rate using simple potometers, leaf impressions, epidermal peels, and grids for determining surface area Key concepts Observation and experiment

Demonstrate the use (or show diagrams) of a standard commercial potometer to measure water uptake (e.g. Thoday). (W) (Basic) o Discuss the reasons for: a slanting cut across the leafy shoot; submerging in

water; use of petroleum jelly round the joint; drying leaves. (W) (Challenging)

Practical: learners make a simple potometer using a long piece of capillary tubing that has a short length of rubber tubing attached at one end. The whole apparatus can be supported vertically. o Learners record the height of the air/water meniscus at suitable time

intervals. (P) (I) (Basic) o Discuss how to make results quantitative, e.g. using grids to determine the

surface area of leaves; using the volume of a cylinder to calculate the volume of water taken up. (W) (Basic)

Extension practical: learners enclose part of a plant inside a plastic bag and use data-logging equipment and a humidity-recording sensor to investigate the effect of transpiration on humidity. (P) (I) (Challenging)

Learners plan and/or carry out a controlled investigation into the effect of wind speed, temperature or light on the rate of transpiration.

Practical booklet 6 Online http://www.mhhe.com/biosci/genbio/virtual_labs/BL_10/BL_10.html http://www.mikecurtis.org.uk/Potometer/potometer.html http://www.saps.org.uk/secondary/teaching-resources/299-measuring-stomatal-density- Textbooks/Publications King p.142-146 Siddiqui p. 140-144, 146-147

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transpiration.html



http://www.mhhe.com/biosci/genbio/virtual_labs/BL_10/BL_10.html

http://www.mhhe.com/biosci/genbio/virtual_labs/BL_10/BL_10.html

http://www.mikecurtis.org.uk/Potometer/potometer.html

http://www.mikecurtis.org.uk/Potometer/potometer.html

http://www.saps.org.uk/secondary/teaching-resources/299-measuring-stomatal-density-




V3.1 57


o Learners present results (or are given results) in graphical form and give explanations for the shape of the graph. (P) (I) (Challenging)

Learners make temporary slides of epidermal strips from leaves of different species (use nail varnish or ‘new skin’ liquid plaster and peel off when dry). (I) (Basic)

Practical booklet 6 is designed to develop some of the practical skills (listed in the Teacher’s practical notes) assessed in paper 3.

Note

Remind learners that potometers measure rates of water uptake only and that a cut end of a stem is not the same as uptake via root hairs.

If a potometer is placed on a balance sensitive to small changes in mass, then it is possible to measure water uptake and transpiration.

7.2.f make annotated drawings, using prepared slides of cross-sections, to show how leaves of xerophytic plants are adapted to reduce water loss by transpiration Key concepts Natural selection, Organisms in their environment

Explain the terms mesophyte, hydrophyte and xerophyte and discuss ways in which plants can reduce their water loss. (W) (Basic)

Learners consider the mesophyte leaf and give comparative descriptions (e.g. thicker waxy cuticle, fewer stomata per unit area of leaf, etc.) using diagrams of leaves from a range of xerophytes. (P) (I) (Basic)

Learners use prepared slides of cross-sections of leaves of xerophytes to make annotated plan diagrams and detailed drawings. (I) (Basic) o Learners describe features and explain how each helps to reduce water loss.

(I) (Challenging) o Extend this to a circus of activities with, e.g. living examples; photographs

and photomicrographs; Bioscope; microscope slides; electron micrographs. (P) (I) (Challenging)

Learners make temporary slides of epidermal strips from leaves of mesophytes and xerophytes and estimate the number of stomata per unit area to make quantitative comparisons. (I) (Challenging) o Extension: some may know how to use the t-test to see if differences are

significant (not required at AS Level). (P) (I) (Challenging)

CD-ROM Bioscope – has suitable images. Online www.worldofteaching.com/powerpoints/biology/Xerophytes.ppt Textbooks/Publications Bio Factsheet 29: Plant and animal adaptations to dry habitats Bio Factsheet 84: Xerophytes and hydrophytes

7.2.g state that assimilates, such as sucrose and amino acids, move between sources (e.g. leaves and

Explain the term assimilates and discuss examples. (W) (Basic)

Introduce translocation as the movement of assimilates from the source (area where they are produced) to the sink (area where they are used / stored). o As an example, state that sucrose is loaded into phloem at the source, and

Online http://leavingbio.net/FLOWERING%20PLANTS.htm

http://www.worldofteaching.com/powerpoints/biology/Xerophytes.ppt

http://www.worldofteaching.com/powerpoints/biology/Xerophytes.ppt




V3.1 58


storage organs) and sinks (e.g. buds, flowers, fruits, roots and storage organs) in phloem sieve tubes Key concepts Cells as the units of life, Biochemical processes

then removed at the sink. o Learners suggest source and sink locations within the plant. (W) (Basic)

Note

Learners should also be familiar with the term photosynthates.

Textbook/Publications King p.146-147 Siddiqui p.135-136 Past Papers Paper 23, June 2011, Q5 (b)(ii)

7.2.h explain how sucrose is loaded into phloem sieve tubes by companion cells using proton pumping and the co-transporter mechanism in their cell surface membranes Key concepts Cells as the units of life, Biochemical processes

Use learner knowledge of membranes and transport mechanisms to describe and explain the events that occur. (W) (Challenging)

Learners write out a set of cards containing relevant points and practise re-ordering them to give a sequential account. o These could range from main points to a detailed account (see table for

examples). (P) (I) (Basic) (Challenging) o Learners write an account from memory. (F)

H+ actively pumped out of companion

cells ATP required

concentration of H+ builds up outside

the membrane membrane impermeable to H

+ so

they cannot diffuse back in

H+ diffuses back in via a membrane

carrier protein down the electrochemical gradient

cotransport of sucrose occurs H+ and sucrose bind to the

protein (conformational change occurs)

sucrose diffuses into phloem sieve tube element

via plasmodesmata

Note

Emphasise that the entry of sucrose into the phloem sieve tube is passive but the whole process is sometimes described as ‘active loading’.

Online http://www.uic.edu/classes/bios/bios100/lectf03am/sucrosepump.jpg Past Papers Paper 23, June 2011, Q5 (c) Paper 21, Nov 2011, Q5 (b) Paper 22, Nov 2011, Q6 (b)

7.2.i explain mass flow in phloem sap down a hydrostatic pressure gradient from source to sink

Learners sort out cards (prepared by you) containing details such as below before making notes. (P) (I) (Basic)

Online http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter38/animation_-

http://www.uic.edu/classes/bios/bios100/lectf03am/sucrosepump.jpg



http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter38/animation_-_phloem_loading.html




V3.1 59



at the source, sucrose enters the phloem sieve tube

this lowers the water potential

this draws (extra) water into the sieve tube by osmosis

this increases the hydrostatic pressure

at the sink, sucrose leaves the phloem sieve tube

water follows osmotically

the hydrostatic pressure at the source is higher than at the sink

fluid / phloem sap moves from source to sink

down this pressure gradient

by mass flow

Note

Learners should understand that phloem translocates soluble organic compounds.

_phloem_loading.html Textbook/Publications Bio Factsheet 132: Phloem. Past Papers Paper 23, June 2011, Q5 (c) Paper 21, Nov 2011, Q5 (b)

7.1.d relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions Key concepts Cells as the units of life

For xylem vessel elements, use diagrams to aid a ‘structure to function’ discussion. Recall the role of xylem in the transport of water and mineral ions and introduce the need for lignification (see also 7.2.a) because of the tension created by the transpiration pull. o Learners suggest other functions of lignin and continue to provide other

examples of structure to function. (W) (Challenging) o Learners match statements about structure to statements about function. The

activity could be divided into the main points and additional points. (P) (I) (Basic) (Challenging)

Learners use resources (see also 7.1.c) to label diagrams of phloem sieve tube elements and companion cells. (I) (Basic) o Learners point out the relationship between structure and function for these

two cell types. (W) (Basic) o Learners make bullet-pointed notes, using one colour for a structural detail

and a different colour for a link to a function. (I) (Challenging)

Note

It is now believed that protein strands are not present in living, functioning

CD-ROM Bioscope – useful for this section. Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PlantTissues.html http://leavingbio.net/FLOWERING%20PLANTS.htm http://www.mhhe.com/biosci/pae/botany/histology/html/ptmodov.htm Textbooks/Publications Bio Factsheet 19: Plant tissues Bio Factsheet 146: Tracheids, vessels and sieve tubes











V3.1 60


phloem tissue. Bio Factsheet 132: Phloem Past Papers Paper 23, June 2011, Q5 (a) Paper 22, June 2013, Q2 (a)

8.1.a state that the mammalian circulatory system is a closed double circulation consisting of a heart, blood vessels and blood Key concepts Cells as the units of life

Display an image giving an overview of the whole circulatory system and check that learners can describe what is meant by pulmonary and systemic circulations. (W) (Basic)

Use a question and answer session to determine that arteries carry blood away from the heart and veins towards the heart. (W) (Basic)

Extension (useful for later studies): discuss names given to blood vessels serving organs e.g. pulmonary + lungs; coronary + heart, hepatic + liver; renal + kidney. (W) (Basic)

Learners make brief written notes explaining closed circulation and double circulation. (I) (Basic)

Learners label diagrams of double circulation, including the heart chambers, the two types of circulation and the names of the main blood vessels. (I) (Basic)

Learners describe the journey made by a red blood cell in one complete circuit of the mammalian blood system. (H) (F) (Basic)

Extension: learners research and contrast the mammalian circulatory system with organisms organised differently, e.g. insect, squid, fish and amphibians. Search online for images of diagrams of insect, fish, amphibians and squid circulatory systems. (I) (Challenging)

Online http://www.bbc.co.uk/schools/gcsebitesize/pe/appliedanatomy/0_anatomy_circulatorysys_rev1.shtml http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AnimalHearts.html

http://www.bbc.co.uk/schools/gcsebitesize/pe/appliedanatomy/0_anatomy_circulatorysys_rev1.shtml



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AnimalHearts.html




V3.1 61


8.1.b observe and make plan diagrams of the structure of arteries, veins and capillaries using prepared slides and be able to recognise these vessels using the light microscope Key concepts Cells as the units of life, Observation and experiment

Gauge learner knowledge of the basic structure of arteries, veins and capillaries with a brainstorming session before providing labelled diagrams. (W) (Basic)

Learners study photomicrographs of (muscular) arteries and veins (TS), and an electron micrograph of capillaries. Learners label the layers and, with prompting, annotate with details. (W) (I) (Basic)

Learners observe prepared TS slides, and draw labelled plan diagrams. Practise measurement using an eyepiece graticule. (I) (Basic) (Challenging)

Extension: learners investigate the elasticity of blood vessels by suspending weights on sections of arteries and veins. (P) (Challenging)

Learners carry out research into other types of blood vessels, including elastic arteries, arterioles and venules (stress this is not required learning). (H) (Challenging)

Learners sort out statements (prepared by you) into three columns for each of the three blood vessel types. (F)

CD-ROM Bioscope – has appropriate slides. Online http://sln.fi.edu/biosci/vessels/vessels.html http://www.histology.leeds.ac.uk/circulatory/arteries.php http://www.nuffieldfoundation.org/practical-biology/elastic-recoil-

arteries-and-veins

http://library.med.utah.edu/WebPath/CVHTML/CVIDX.html Textbooks/Publications Siddiqui p.175-177

8.1.c explain the relationship between the structure and function of arteries, veins and capillaries Key concepts Cells as the units of life

Learners construct a table showing the relationship between structure to function for each of the three blood vessel types. (I) (Challenging)

Learners label the layers on diagrams of an artery, vein and capillary in TS, and then annotate to link structure to function. (F)

Online http://nsb.wikidot.com/2-2-3-compare-the-structure-of-arteries-capillaries-and-vein

http://sln.fi.edu/biosci/vessels/vessels.html

http://sln.fi.edu/biosci/vessels/vessels.html

http://www.histology.leeds.ac.uk/circulatory/arteries.php

http://www.histology.leeds.ac.uk/circulatory/arteries.php

http://www.nuffieldfoundation.org/practical-biology/elastic-recoil-arteries-and-veins



http://library.med.utah.edu/WebPath/CVHTML/CVIDX.html


http://nsb.wikidot.com/2-2-3-compare-the-structure-of-arteries-capillaries-and-vein




V3.1 62


8.1.d observe and draw the structure of red blood cells, monocytes, neutrophils and lymphocytes using prepared slides and photomicrographs Key concepts Cells as the units of life, Observation and experiment

Learners observe blood cells using the light microscope or use other images. (I) (Basic) o Learners draw labelled diagrams of the different cell types and make tables to

compare: red blood cells with white blood cells; monocytes with neutrophils. (I) (Challenging)

Learners use resources to explain how the structural features of a red blood cell are related to the function of oxygen transport. (I) (Challenging)

Note

The terms erythrocyte and leucocyte should also be mentioned (not required learning).

The function of the white blood cells and details of B-lymphocytes compared to T-lymphocytes are covered in Unit 5.

To help later understanding, explain that monocytes take on a different appearance when they mature to become macrophages, and that these cells are usually in locations other than blood tissue.

CD-ROM Bioscope – has appropriate images. Online http://micro.magnet.fsu.edu/index.html http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab6/Lab6.htm Textbooks/Publications King p.120-122, 164-165 Siddiqui p. 179-182 Bio Factsheet 62: Animal tissues I – epithelia and blood Bio Factsheet 36: Structure and function of blood and lymph Past Papers Paper 22, June 2011, Q3 (a)(b)

8.1.e state and explain the differences between blood, tissue fluid and lymph Key concepts Cells as the units of life

Brainstorm the composition of blood and discuss the need for exchange with cells. (W) (Basic) o Discuss how and why the concentrations of substances in blood, such as

oxygen, carbon dioxide and dissolved glucose, can vary. (W) (Challenging)

Explain how pressure changes from the arterial to the venous end of the capillary network. Ask for suggestions, with reasons, as to which of the components would be able to leave the network. (W) (Challenging)

Learners use resources to label and annotate a diagram of a capillary network, including explanations of how tissue fluid and lymph are formed and arrows to show direction of blood flow, formation of tissue fluid and formation of lymph. (I) (Challenging) o Learners add arrows of different colours or styles (use a key) to represent the

movement of substances such as dissolved glucose and amino acids, oxygen and carbon dioxide. (I) (Basic)

Textbooks/Publications Bio Factsheet 36: Structure and function of blood and lymph Bio Factsheet 89: Tissue fluid Bio Factsheet 171: Answering exam questions: the formation and drainage of lymph Past Papers Paper 21, June 2011, Q2 (b)



http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab6/Lab6.htm




V3.1 63


Learners construct a comparative table of differences between blood, tissue fluid and lymph. (H) (F)

Note

Highlight the difference between blood and blood plasma.

8.2.a describe the external and internal structure of the mammalian heart Key concepts Cells as the units of life

Learners check their knowledge of the internal structure of the heart by adding as many labels as possible to a diagram. Go through this, allowing learners to add any missing e.g. tendinous cords and papillary muscles, sinoatrial node, atrioventricular node and Purkyne tissue. (I) (Basic)

Show learners images of the external structure of the heart and agree labels. (W) (Basic)

Learners match up a set of labels with a set of descriptions. (I) (Basic)

Learners practise adding labels, with descriptive features, to a range of internal and external diagrams of the heart. (H) (F) (Basic) (Challenging)

Learners study models of the heart or dissect a heart (or observe) obtained from butchers, abattoirs or suppliers. (G) (P) (I) (Basic) (Challenging) o Heart models are useful for learners to get a 3-D understanding if dissection

is not carried out.

Note

Hearts obtained for dissection have often lost their blood vessels and some or all of their atria. Obtaining heart and lungs may provide a more complete heart (useful for the gross structure of the gas exchange system, studied later).

Online http://www.learnerstv.com/animation/animation.php?ani=321&cat=biology http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_anatomy.html http://www.sciencelearn.org.nz/Contexts/See-through-Body/Sci-Media/Animations-and-Interactives/Label-the-heart http://library.med.utah.edu/WebPath/CVHTML/CVIDX.html Textbooks/Publications King p.128-130 Siddiqui p.173-174 Bio Factsheet 35: Structure and function of the mammalian heart

http://www.learnerstv.com/animation/animation.php?ani=321&cat=biology



http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_anatomy.html

http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_anatomy.html

http://www.sciencelearn.org.nz/Contexts/See-through-Body/Sci-Media/Animations-and-Interactives/Label-the-heart







V3.1 64


8.2.b explain the differences in the thickness of the walls of the different chambers in terms of their functions with reference to resistance to flow Key concepts Cells as the units of life

Learners complete a short test or sort statements into the correct order to remind them about the pathway of blood in one complete circuit of the body. (F)

Explain that the differences in pressure between the left and right ventricles are related to the ability to overcome resistance to flow by the blood vessels as blood travels to the body tissues. o Learners volunteer that there is a far lower resistance to flow in the

pulmonary circulation than in the systemic. o Remind learners that the thicker the wall of a heart chamber, the more

cardiac muscle there is to generate force when it contracts.

Relate the thinner atrial walls (compared to the thicker ventricle walls) to the much lower resistance that blood has to overcome to travel the short distance to the ventricles. (W) (Basic)

Note Pulmonary capillaries are very delicate (very small diameter) so an increase from normal pressure of blood leaving the right ventricle increases the likelihood of damage.

Online http://www.physiologymodels.info/cardiovascular/arterioles.htm Past Papers Paper 22, June 2013, Q6 (b)

http://www.physiologymodels.info/cardiovascular/arterioles.htm

http://www.physiologymodels.info/cardiovascular/arterioles.htm


V3.1 65


8.2.c describe the cardiac cycle (including blood pressure changes during systole and diastole) Key concepts Cells as the units of life

A discussion should switch the focus from a description of one complete circuit of the body to one cardiac cycle. o Remind learners that a decrease in volume of a heart chamber when the

cardiac muscle contracts means an increase in blood pressure within the chamber. (W) (Basic)

o Associate the events occurring during one cardiac cycle to changes in blood pressure , explaining that valves are pushed open and shut by differences in pressure on either side. (W) (Challenging)

Learners produce a table describing the sequence of events (including the status of the valves) occurring in one cardiac cycle and highlighting that both sides of the heart contract and relax in unison: (I) (Challenging)

right side of heart left side of heart

Learners annotate a set of diagrams (prepared by you) showing the heart during one cardiac cycle. (F)

Use OHP overlays / PowerPoint presentation to build up a graph showing the pressure and volume changes on one side of the heart (left side is most commonly shown). o Add heart diagrams below the x-axis in the different stages of the cycle,

corresponding to the correct times on the graph. o Learners volunteer explanations throughout. (W) (Challenging)

Learners annotate a pressure change graph describing the event in the cardiac cycle that correlates to the change shown on the graph (including points at which named valves open and shut). (I) (Challenging)

Learners practise extracting information and interpreting questions based on pressure change graphs (prepared by you). (I) (F) (Basic) (Challenging)

Note ECGs (not required learning), accompanied by explanations, may be given as stimulus material in a question.

Online http://www.pbs.org/wgbh/nova/eheart/human.html http://library.med.utah.edu/kw/pharm/hyper_heart1.html Past Papers Paper 23, Nov 2011, Q2 (b)

http://www.pbs.org/wgbh/nova/eheart/human.html

http://www.pbs.org/wgbh/nova/eheart/human.html

http://library.med.utah.edu/kw/pharm/hyper_heart1.html

http://library.med.utah.edu/kw/pharm/hyper_heart1.html


V3.1 66


8.2.d explain how heart action is initiated and controlled (reference should be made to the sinoatrial node, the atrioventricular node and the Purkyne tissue, but not to nervous and hormonal control) Key concepts Cells as the units of life

Use explanations, interspersed with questions requiring thoughtful suggestions, to present the following ideas: o The heart is myogenic (initiates heart beat without receiving nerve impulses

from outside). o The sinoatrial node (SAN - primary pacemaker) initiates muscle cell

depolarisation and atrial systole.

The insulating ring of non-conducting (connective) tissue (fibrous ring): prevents the atria and ventricles from contracting at the same time; forces the wave of depolarisation to pass through the atrioventricular node (AVN), delaying its passage so the atria complete systole before ventricular systole begins.

The Purkyne tissue passes the depolarisation down to the apex of the heart so that the ventricles contract from the bottom up, squeezing blood out up the arteries. (W) (Challenging)

In the correct locations on a diagram of the heart, learners number the events occurring in sequence, making notes underneath for each number. (I) (Basic)

Learners place in sequence statements of each of the events occurring, starting with the SAN. (P) (I) (Basic) o Create a second column so that statements of cardiac cycle events

correspond with the timing. (P) (I) (Challenging)

Note

‘Wave of excitation’ or ‘impulses’ are acceptable terms, not signal, wave, pulse, message or nerve impulse.

Learners should understand that the wave of depolarisation spreads across the network of cardiac muscle fibres to bring about systole, and that the fibres do not fatigue (no other details of cardiac muscle required).

Online http://hyperphysics.phy-astr.gsu.edu/hbase/biology/sanode.html http://www.nhlbi.nih.gov/health/health-topics/topics/hhw/ Textbooks/Publications Bio Factsheet 139: Answering exam questions on the heart Bio Factsheet 7: Comparing transport in plants and animals. Past Papers Paper 23, Nov 2011, Q2 (a)

9.1.a describe the gross structure of the human gas exchange system. Key concepts Cells as the units of life

Agree that the mammalian transport system carries the respiratory gases, oxygen and carbon dioxide and contrast this with plant vascular tissue (not involved with gas transport). Explain that the gas exchange system facilitates exchange with the external environment. (W) (Basic)

Learners revise previous knowledge by labelling familiar structures on a diagram of the human gas exchange system, using resources to complete labelling and add annotations. (I) (Basic) o Ensure learners know that the specialised gas exchange surface is the

alveolus. (I) (Basic)

Textbooks/Publications Siddiqui p.183

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/sanode.html



http://www.nhlbi.nih.gov/health/health-topics/topics/hhw/

http://www.nhlbi.nih.gov/health/health-topics/topics/hhw/


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9.1.b observe and draw plan diagrams of the structure of the walls of the trachea, bronchi, bronchioles and alveoli indicating the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle, squamous epithelium and blood vessels Key concepts Cells as the units of life

Project images or show photomicrographs of the named structures and give guidance as to how to identify the named structures and learn about the distribution of the named features. (W) (Basic)

Learners observe, interpret, and draw plan diagrams of prepared slides. (I) (Challenging) o Learners also identify cilia, mucous glands and elastic fibres to prepare for

9.1.c. (I) (Challenging) o Learners complete a table (tick = present, cross = absent) such as below. (I)

(Challenging) o Learners compare their diagrams and table with textbook versions. (I) (Basic)

structure cartilage ciliated epithelium

goblet cells smooth muscle

squamous epithelium

blood vessels

trachea

bronchus

bronchiole

alveoli

Learners label diagrams of sections through the trachea, bronchus and bronchiole and complete blank tables as above. (F)

Note

Learners should know the singular and plural: bronchus and bronchi; alveolus and alveoli.

Explain that there are only a few goblet cells in the bronchiole (some textbooks may state none are present) and discuss the reason for this, i.e. avoiding mucus hindering gas exchange in the alveoli.

Online http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/Histo15.html http://micro.magnet.fsu.edu/index.html http://library.med.utah.edu/WebPath/HISTHTML/EM/EM040.html Textbooks/Publications King p.89-91 Siddiqui p.184-185

9.1.c describe the functions of cartilage, cilia, goblet cells, mucous glands, smooth muscle and elastic fibres and recognise these cells and tissues in prepared slides, photomicrographs and electron micrographs of the gas exchange system

Discuss the reasons for the distribution of the various features within the gas exchange system by explaining their functions. (W) (Basic)

Learners match statements: features with correct functions. (I) (Basic)

Reinforce learning by providing photomicrographs and electron micrographs for learners to identify the features. (P) (I) (Challenging)

Learners give written explanations linking the presence / location of the features in the different areas of the gas exchange system to their function. (F)

Online http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/Histo15.html http://micro.magnet.fsu.edu/index.html http://library.med.utah.edu/WebPath/HISTHTML/EM/EM040.html

http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/Histo15.html















V3.1 68



Textbooks/Publications King p.89-91 Siddiqui p.184-185 Past Papers Paper 21, June 2011, Q1 Paper 22, Nov 2011, Q1

9.1.d describe the process of gas exchange between air in the alveoli and the blood Key concepts Cells as the units of life

Discuss the roles of blood flow and ventilation in maintaining diffusion gradients for oxygen and carbon dioxide between the alveoli and blood. o Incorporate a question and answer session so learners can apply knowledge

of the function of haemoglobin (Unit 1). (W) (Basic)

Learners draw and annotate diagrams with key features of the process, adding arrows to indicate the direction of exchange of oxygen and carbon dioxide. (I) (Challenging)

Learners write a short account of how concentration gradients are maximised for efficient gas exchange. (I) (Basic)

Learners produce a written description explaining gas exchange in terms of the structure of the alveolus and capillary and diffusion across cell surface membranes. (I) (Challenging) o The account should make clear the difference between diffusion across

alveolar and capillary walls and diffusion across membranes.

Using a diagram of an alveolus and associated capillaries, learners give an account of how the structure of the gas exchange surface is adapted for its function. (F)

Note

A common written error in examinations is to state that diffusion occurs across ‘epithelial cell walls’ or ‘the cell walls of the capillary’.

It is not sufficient to state that red blood cells take up oxygen: learners should refer to oxygen uptake by haemoglobin in red blood cells.

Online http://www.johnwiley.net.au/highered/interactions/media/Respiration/content/Respiration/resp1a/frameset.htm http://www.johnwiley.net.au/highered/interactions/media/Respiration/content/Respiration/resp2a/bot.htm Textbooks/Publications Bio Factsheet 26: Gas exchange in animals

8.1.f describe the role of haemoglobin in carrying oxygen and carbon dioxide

Use a question and answer session to revise haemoglobin structure (Unit 1) before providing further details of oxygen binding and carriage and oxygen release. (W) (Challenging)

Online http://www.biology4all.com/resources_library/details.asp?ResourceI

http://www.johnwiley.net.au/highered/interactions/media/Respiration/content/Respiration/resp1a/frameset.htm




http://www.johnwiley.net.au/highered/interactions/media/Respiration/content/Respiration/resp2a/bot.htm







V3.1 69


with reference to the role of carbonic anhydrase, the formation of haemoglobinic acid and carbaminohaemoglobin (details of the chloride shift are not required) Key concepts Cells as the units of life, Biochemical processes

With teacher prompting, learners construct a diagram summarising the carriage of carbon dioxide by haemoglobin at the respiring tissue (ensure they understand that the reverse happens in the lung tissue). (I) (Challenging) o The labelled diagram to include the red blood cell, the endothelium with

pores, and the body cells. o Discuss in stages, with learners adding information, the sequence of events

occurring.

Discuss the importance of carbonic anhydrase (recall enzyme knowledge), also highlighting that haemoglobin is not the only protein found in red blood cells. (W) (Basic)

Learners produce a written explanation of the events occurring in the: respiring tissues, using a diagram as stimulus material; in the lungs. (H) (F) (Challenging)

Learners explain the roles of haemoglobin in the carriage of carbon dioxide in buffering hydrogen ions and transporting carbon dioxide directly as carbaminohaemoglobin. (I) (Challenging)

Note Learners should not describe oxygen binding to haemoglobin as ‘bonding’.

D=8 http://www.mrothery.co.uk/circulation/circulationotes.htm#BLOOD Textbooks/Publications Bio Factsheet 175: Haemoglobin: structure & function Past Papers Paper 21, June 2011, Q2 (a)(c) Paper 22, June 2011, Q3 (d)(e)

8.1.g describe and explain the significance of the oxygen dissociation curves of adult oxyhaemoglobin at different carbon dioxide concentrations (the Bohr effect) Key concepts Cells as the units of life, Biochemical processes

Introduce the oxygen dissociation curve step-by-step (a difficult concept to grasp), returning to previous steps if necessary. o Introduce partial pressure as a measure of concentration and ‘availability’ of

oxygen and the percentage saturation of haemoglobin as ‘affinity’ for oxygen. o Explain that the oxygen dissociation curve is constructed from results of

experimental measurements. o Explain the loading of oxygen in the lung (see 8.1.f). o Explain the release of oxygen (i.e. oxyhaemoglobin dissociation) as a result

of the lower partial pressure in other body tissue (resting). (W) (Challenging)

Learners annotate their own diagrams of the oxygen dissociation curve of adult haemoglobin. (I) (Challenging)

Learners suggest why the steep part of the curve is important and beneficial (efficient unloading in partial pressures common in respiring tissues). (W) (Challenging)

Explain the Bohr shift in relation to carbon dioxide carriage by haemoglobin, using a summary diagram from 8.1.f. o Explain that haemoglobin dissociates to a greater extent in working tissue as

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=8 http://www.mrothery.co.uk/circulation/circulationotes.htm#BLOOD http://www.wiley.com/college/fob/anim/ http://www.wiley.com/college/fob/quiz/quiz07/7-7.html http://www.wiley.com/college/fob/quiz/quiz07/7-12.html Textbooks/Publications Bio Factsheet 175: Haemoglobin: structure & function Bio Factsheet 9: Oxygen


http://www.mrothery.co.uk/circulation/circulationotes.htm#BLOOD







http://www.wiley.com/college/fob/anim/

http://www.wiley.com/college/fob/anim/

http://www.wiley.com/college/fob/quiz/quiz07/7-7.html





V3.1 70


the presence of increased carbon dioxide concentrations facilitates the unloading of ‘more’ oxygen by haemoglobin.

o Ask learners to suggest the significance of the greater dissociation (greater need of tissues for oxygen as they are more actively respiring). (W) (Challenging)

Learners complete worksheets involving data extraction and interpretation of the curve. (P) (I) (F) (Challenging)

Extension: learners research (using textbooks/internet), consider and explain the oxygen dissociation curves of myoglobin and foetal haemoglobin. (H) (Challenging)

dissociation curves Past Papers Paper 21, June 2011, Q2 (a)(c) Paper 22, June 2011, Q3 (d)(e) Paper 21, June 2011, Q2 (d) Paper 23, June 2011, Q4

8.1.h describe and explain the significance of the increase in the red blood cell count of humans at high altitude Key concepts Cells as the units of life, Organisms in their environment

Learners make bullet-point notes after discussing how an increase in red blood cell count is linked to an increase in haemoglobin, and how this compensates for the lower saturation that occurs at high altitudes (hence ensuring that body tissues receive sufficient oxygen). (W) (I) (Basic)

Learners complete a worksheet (prepared by you) to make comparisons of red blood cell counts at different altitudes, including giving percentage changes. (H) (Basic) (Challenging)

Extension: learners research the benefits to athletes of training at high altitude, or investigate if communities who have always lived at high altitude are different to others. (I) (H) (Challenging)

Online http://www.sportsci.org/traintech/altitude/wgh.html Textbooks/Publications Bio Factsheet 149: High altitude biology

http://www.sportsci.org/traintech/altitude/wgh.html

http://www.sportsci.org/traintech/altitude/wgh.html


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Unit 5: Disease and protection against disease


Some introductory knowledge of sickle cell anaemia would be useful, which may have arisen from additional information acquired when learning about sickle cell haemoglobin in Unit 1, or about mutations in Unit 3. Also from Unit 1, an appreciation of protein structure to function will help when studying antibody structure and function. Learners should have a good understanding of cell structure, the role of cell surface membrane receptors and the mechanism of endocytosis from Unit 2. They should appreciate the difference between eukaryotes, prokaryotes and viruses. An understanding of how uncontrolled cell division may result in a tumour, studied in Unit 3, is required. From Unit 4, learners should be familiar with the histology of the gas exchange system and have knowledge of white blood cells. Context

Previous units have looked at living organisms on the molecular and cellular scale, before moving on to organs and systems. Disease is an outcome of the malfunctioning of cells through altered biochemical processes. Infectious diseases show how humans interact with pathogens. These interactions are one component of the key concept Organisms in their environment. A multicellular organism must organise, control and coordinate activities so that they have defence mechanisms and can develop immunity from disease. A link is provided to another key concept, Natural selection, with a consideration of the development of antibiotic resistance by bacteria. Learners are also introduced to monoclonal antibodies, one important aspect of biotechnology. Monoclonal antibodies are the result of observation and experiment, which is a key concept. Outline

An understanding is gained of what is meant by disease and what the differences are between infectious and non-infectious diseases. Learners are provided with examples of non-infectious disease by learning more about sickle cell anaemia and considering how tobacco smoking affects the gas exchange and cardiovascular systems. Five infectious diseases of global importance are studied in some detail: cause; transmission; prevention and control, including the use of antibiotics. The unit continues with a consideration of the factors that influence the global patters of TB, malaria and HIV/AIDS. Smallpox is introduced as an infectious disease so that learners can appreciate how vaccination programmes have helped to eradicate the disease. Penicillin is studied as an example of an antibiotic and learners then progress to study antibiotic resistance and consider the steps taken to alleviate this problem. There are good opportunities within this unit for learners to develop their skills in data analysis, particularly with respect to disease statistics. Natural and artificial immunity is studied, including the structure and function of antibodies. Learners will be provided with more detail about phagocytes and the way in which they function to protect against disease. The events occurring during a specific immune response are covered. A brief consideration is given to the outcome to the body when the immune system fails to work correctly, using myasthenia gravis as an example. An account of the production of monoclonal antibodies and how they are used in the diagnosis of disease and treatment of disease is included. The unit concludes with a study of vaccination and a comparison of the effectiveness of vaccination programmes in the prevention and control of the infectious diseases studied. Teaching time



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10.1.a define the term disease and explain the difference between an infectious disease and non-infectious disease (limited to sickle cell anaemia and lung cancer) Key concepts Cells as the units of life, Biochemical processes, Natural selection

Ask learners for their ideas for the definition of disease (see examples below). o An abnormal condition affecting an organism, which reduces the

effectiveness of its function. o An absence of one or more of physical, social and mental well-being. (W)

(Basic)

Learners name common infectious diseases and suggest the type of causative organism, the pathogen (use both terms). o Add examples to cover bacteria, viruses and fungi. o Introduce protoctists as pathogens (causative pathogen of malaria) using

simple ideas (e.g. eukaryotes, many are unicellular, organisms not fitting into other groups / kingdoms). (W) (Basic)

Learners give examples of non-infectious diseases. o Ensure they include diseases of the gas exchange system (linked with

tobacco smoking) and sickle cell anaemia. o Discuss the cause of sickle cell anaemia (see 6.2.c), Unit 3)). (W) (Basic)

Learners explain why lung cancer and sickle cell anaemia are not considered to be infectious diseases.

Learners summarise discussions in a comparison table or in comparative sentences. (I) (Basic)

Extension: learners research the term pathogen, e.g. ‘a biological agent (e.g. a virus, bacterium, fungus or protoctist) that causes disease and has proteins (foreign/non-self antigens) as part of its structure that are different from those of the human host’.

Note

‘Germs’ as an alternative to ‘pathogens’ is not acceptable.

A common error is to use the term disease rather than pathogen, e.g. “the disease enters cells” or to name the disease instead of the pathogen e.g. “malaria enters red blood cells”.

Online http://edis.ifas.ufl.edu/in722 Textbooks/Publications Bio Factsheet 40: Disease and defence Past Papers Paper 21, Nov 2011, Q4 (b) Paper 22, Nov 2011, Q2 (b)(i)

9.2.a describe the effects of tar and carcinogens in tobacco smoke on the gas exchange system with reference to lung cancer and chronic

In a question and answer session, learners explain why chronic bronchitis and emphysema are also non-infectious diseases (in addition to lung cancer). (W) (Basic)

Check learner knowledge of the terms carcinogen and carcinogenic. (W) (Basic)

Online http://www.lung.ca/diseases-maladies/index_e.php http://library.med.utah.edu/WebPath/LUNGHTML/LUNGIDX.html

http://edis.ifas.ufl.edu/in722

http://www.lung.ca/diseases-maladies/index_e.php

http://www.lung.ca/diseases-maladies/index_e.php

http://library.med.utah.edu/WebPath/LUNGHTML/LUNGIDX.html

http://library.med.utah.edu/WebPath/LUNGHTML/LUNGIDX.html


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obstructive pulmonary disease (COPD) Key concepts Cells as the units of life, DNA, the molecule of heredity, Observation and experiment

Learners volunteer examples before projecting/showing the long list of carcinogens in tobacco smoke. (W) (Basic) o Explain that lung cancer may happen naturally, but the risk is increased by

a range of different environmental factors, identifying tar as a main causative agent. (W) (Basic)

Relate back to Unit 3 and ask learners to write out an outline sequence of consequential events leading to a tumour and the development of cancer. (W) (I) (Basic)

Discuss the imprecision in the statement: “Cigarettes cause lung cancer” and ask learners to suggest improvements, e.g. “There is a correlation between tobacco smoking and the development of lung cancer”, “Tar in tobacco smoke is known to be a cause of lung cancer”. (W) (Challenging)

Learners investigate how carcinogens can promote the mutation of two important types of genes involved in the control of cell division, proto-oncogenes (form oncogenes, associated with the development of cancer) and tumour suppressor genes (may mutate so that they can no longer act as a control). (W) (I) (H) (Challenging)

Name chronic bronchitis and emphysema as the two diseases of COPD. (W) (Basic) o For each, learners make short notes summarising the changes that occur

in the gas exchange system that lead to the symptoms of disease. (I) (Challenging)

Extension: learners use data from the WHO website to practise data handling and investigate the occurrence of deaths from cancers. (P) (I) (Basic) (Challenging)

Learners collect, display and analyse data about a smoking-related disease of the gas exchange system and give a short presentation to the class. (W) (H) (Challenging)

Note

Explain the difference between a mutagen (an agent that increases the mutation rate of DNA) and a carcinogen (an agent that can cause cancer).

To help make links to changes that occur in the gas exchange system, learners will benefit from an outline of the signs and symptoms that the diseases share in common and those that are characteristic for each disease.

http://www.ash.org.uk/information/facts-and-stats http://www.insidecancer.org/ http://www.cancer.org/cancer/cancercauses/geneticsandcancer/oncogenesandtumorsuppressorgenes/oncogenes-tumor-suppressor-genes-and-cancer-mutations-and-cancer http://www.who.int/en/ http://www.sanger.ac.uk/genetics/CGP/Census/ http://www.parliament.the-stationery-office.co.uk/pa/cm199900/cmselect/cmhealth/27/9120907.htm Textbooks/Publications Bio Factsheet 104: Biological basis of cancer. Past Papers Paper 22, Nov 2011, Q1 (c)(d)(e)

http://www.ash.org.uk/information/facts-and-stats

http://www.ash.org.uk/information/facts-and-stats

http://www.insidecancer.org/

http://www.cancer.org/cancer/cancercauses/geneticsandcancer/oncogenesandtumorsuppressorgenes/oncogenes-tumor-suppressor-genes-and-cancer-mutations-and-cancer





http://www.who.int/en/

http://www.sanger.ac.uk/genetics/CGP/Census/

http://www.sanger.ac.uk/genetics/CGP/Census/

http://www.parliament.the-stationery-office.co.uk/pa/cm199900/cmselect/cmhealth/27/9120907.htm




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9.2.b describe the short-term effects of nicotine and carbon monoxide on the cardiovascular system Key concepts Cells as the units of life, Biochemical processes

Explain what is meant by the term cardiovascular. (W) (Basic)

Introduce carbon monoxide and nicotine as two components of smoke that can easily pass across the alveolar wall to the bloodstream. o Discuss how the presence of these components can cause short-term

effects, which may lead to other short-term effects (consequential outcomes) and to long-term effects. (W) (Basic)

Explain the affinity of haemoglobin to carbon monoxide (links to Unit 4) and the permanency of this association. (W) (Basic) o Learners discuss the consequences of this with respect to: uptake of

oxygen; delivery to tissues (especially the extremities); effect on heart rate. (W) (G) (Basic)

State that carbon monoxide can also cause damage to the endothelial lining, which is a starting point for vascular disease (atheroma/atherosclerosis). (W) (Basic)

Learners make bullet-point notes about the effects of carbon monoxide. (F)

Learners research the short-term effects of nicotine and produce a concept map or spider diagram (with links to consequential effects). o Examples: damage to endothelial lining, which can cause turbulent blood

flow and increase risk of clotting (thrombosis); increase in blood pressure owing to release of adrenaline (can also damage the endothelial lining); making platelets ‘sticky’(increasing platelet aggregation), so increasing thrombosis risk; increased heart rate; vasoconstriction, which can reduce blood flow to extremities; increase in LDLs (low-density lipoprotein). The summary could be in the form of a concept map/spider diagram. (P) (I) (Challenging)

Extension: learners research how the short-term effects can lead to longer term effects (e.g. atheroma and atherosclerosis, peripheral arterial disease). (H) (Challenging)

Note

The addictive effects of nicotine are not related to the cardiovascular system, so are not required.

Online http://www.ash.org.uk/files/documents/ASH_111.pdf http://www.bhf.org.uk/ http://library.med.utah.edu/WebPath/ATHHTML/ATHIDX.html http://library.med.utah.edu/WebPath/CVHTML/CV005.html Textbooks/Publications Bio Factsheet 218: Biology of risk factors 1: Smoking Bio Factsheet 37: Ischaemic (coronary) heart disease (for extension work) Past Papers Paper 22, June 2011, Q6 Paper 22, Nov 2013, Q6 (b)

10.1.b state the name and type of causative

Explain the convention for naming the organisms: upper case (capital) letter for the first letter of the generic name, lower case letter for the specific epithet.

Online http://textbookofbacteriology.net/tube

http://www.ash.org.uk/files/documents/ASH_111.pdf

http://www.ash.org.uk/files/documents/ASH_111.pdf

http://www.bhf.org.uk/

http://library.med.utah.edu/WebPath/ATHHTML/ATHIDX.html

http://library.med.utah.edu/WebPath/ATHHTML/ATHIDX.html

http://library.med.utah.edu/WebPath/CVHTML/CV005.html

http://library.med.utah.edu/WebPath/CVHTML/CV005.html

http://textbookofbacteriology.net/tuberculosis.html


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organism (pathogen) of each of the following diseases: cholera, malaria, tuberculosis (TB), HIV/AIDS, smallpox and measles (detailed knowledge of structure is not required. For smallpox (Variola) and measles (Morbillivirus) only the name of genus is needed) Key concepts Cells as the units of life, Organisms in their environment

(W) (Basic)

You may wish to concentrate on one disease and work through 10.1.b to 10.1.e before moving onto the next disease. Alternatively two to four learners work together (lesson and homework), to research information about one disease and prepare a presentation for the class, sharing notes. (G) (H) (Challenging) o Learners then make learning notes on each of the five diseases. (I) (H)

(Basic)

Learners research the required information and complete the first two columns of a large summary headed table. (I) (H) (Basic)

Learners carry out a mix and match card exercise (prepared by you) with the name of disease, type of causative organism/pathogen, name of causative organism / pathogen. (F)

Note

In their own handwriting learners should underline the species name, in print they are in italics.

A brief discussion of the term species will help understanding (defined in Unit 6).

Learners should spell species names correctly.

For malaria, parasite will be seen in addition to pathogen.

rculosis.html http://textbookofbacteriology.net/cholera.html http://library.med.utah.edu/WebPath/HISTHTML/EM/EM018.html Past Papers Paper 22, Nov 2012, Q4 (a)

10.1.c explain how cholera, measles, malaria, TB and HIV/AIDS are transmitted Key concepts Cells as the units of life, Organisms in their environment

See 10.1.b for group work.

Discuss what is meant by a transmission cycle, noting that the causative organism is transmitted when a disease spreads. o Learners suggest reasons for some diseases spreading more rapidly than

others. o Summarise on a poster learner suggestions as to main modes of

transmission. o Learners assign a mode of transmission to each named disease and write

a paragraph for each. (W) (Basic)

Learners add key points to their summary table. (I) (Challenging)

Note

Ensure learners know the difference between the causative organism of malaria, the protoctist Plasmodium, and the mosquito vector, Anopheles.

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=36

http://textbookofbacteriology.net/tuberculosis.html

http://textbookofbacteriology.net/cholera.html

http://textbookofbacteriology.net/cholera.html






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10.1.d discuss the biological, social and economic factors that need to be considered in the prevention and control of cholera, measles, malaria, TB and HIV/AIDS (a detailed study of the life cycle of the malarial parasite is not required) Key concepts Cells as the units of life, Organisms in their environment, Observation and experiment


Begin with a general discussion, learners suggesting what is meant by ‘social’ factors (relating to human society and interdependence - the idea of benefit to all as a result of cooperation). o Discuss the distinction between prevention and control. (W) (Basic)

Learners study information (provided by you), including statistics, about a recent outbreak of one of the named diseases. (G) (Basic) o Discuss the availability of vaccines and treatments (including drugs) for

the disease. (W) (Basic)

Outline what antibiotics are and when they are useful in the treatment of disease. (W) (Basic)

Learners use information sheets to suggest ways of breaking the transmission cycle for each disease, and the difficulties in making this happen. o Learners consider biological, social and economic factors in relation to

prevention and control. (G) (P) (Challenging)

Learners research where these diseases are currently prevalent and how this affects people in different parts of the world. (I) (Challenging)

Note

Learners should be aware that antibiotics can be antifungal.

Online http://www.who.int/en/ http://www.who.int/research/en/ http://www.cdc.gov/ Past Papers Paper 23, Nov 2011, Q4

10.1.e discuss the factors that influence the global patterns of distribution of malaria, TB and HIV/AIDS and assess the importance of these diseases worldwide Key concepts Cells as the units of life, Organisms in their environment, Observation and experiment


From 10.1.d, learners give reasons why some countries are better able to prevent and control a particular disease. (I) (Basic)

Learners choose one of the named diseases to research and produce a short report. (H) (Challenging) o Learners contribute from their report to a group discussion. (W) (Basic) o Point out how there is often a correlation in disease pattern, e.g. high

incidence of TB in people with HIV/AIDS. (W) (Basic) o Learners make summary learning notes on each disease. (I) (Basic)

Learners fill in details on a partially completed table summarising all the main points for 10.1.b to 10.1.e (see Note). (F)

Note

Display world maps showing the areas most affected by each disease.

Online http://www.cdc.gov/malaria/malaria_worldwide/impact.html http://www.ncbi.nlm.nih.gov/pubmed/21728152 http://www.who.int/hiv/mediacentre/news60/en/

http://www.who.int/en/

http://www.who.int/research/en/

http://www.cdc.gov/

http://www.cdc.gov/malaria/malaria_worldwide/impact.html

http://www.cdc.gov/malaria/malaria_worldwide/impact.html

http://www.ncbi.nlm.nih.gov/pubmed/21728152

http://www.ncbi.nlm.nih.gov/pubmed/21728152

http://www.who.int/hiv/mediacentre/news60/en/

http://www.who.int/hiv/mediacentre/news60/en/


V3.1 77


10.2.a outline how penicillin acts on bacteria and why antibiotics do not affect viruses Key concepts Cells as the units of life, Biochemical processes

Outline the difference between bacteriostatic and bactericidal antibiotics. (W) (Basic)

Explain that the penicillin group of antibiotics are also known as beta lactams (describes their structure). (W) (Basic)

Review learner knowledge of bacterial cell wall structure and use a question and answer session to build up the action of penicillin. o Explain that transpeptidase enzymes (glycoprotein peptidases) catalyse

formation of peptide cross links between peptidoglycan chains, which complete the strength of the cell wall.

o Prompt learners to recall knowledge of enzyme inhibition before they suggest how penicillin acts to inhibit transpeptidases.

o Learners suggest why penicillin is only active against growing bacteria that are laying down new cell wall components. (W) (Challenging)

Display key terms and key points for learners to write a summary of the discussion. (F)

Extension: learners research the other main ways in which antibiotics act and explain why penicillin and other antibiotics do not harm human cells. (I) (Challenging)

Microbiology practical: learners place filter paper discs impregnated with different antibiotics (e.g. Mast rings), or different concentrations of the same antibiotic, onto a Petri dish with nutrient agar inoculated with non-hazardous bacteria (e.g. Bacillus subtilis). o Learners measure zones of inhibition created around the discs on the

lawn of bacteria and compare to determine the efficacy of each antibiotic (or antibiotic concentration). (P) (I) (Challenging)

Learners write a paragraph explaining why antibiotics do not affect viruses (see Unit 2, viral structure), extending this to use HIV as an example. (I) (Challenging) o Remind learners that there are anti-viral drugs effective against HIV. (W)

(Basic)

Online http://www.cellsalive.com/pen.htm http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/penicill.htm http://textbookofbacteriology.net/antimicrobial.html Textbooks/Publications King p.172-173 Siddiqui p.52 Past Papers Paper 22, June 2013, Q3 (b)

10.2.b explain in outline how bacteria become resistant to antibiotics with reference to mutation and selection

Learners suggest changes in bacteria that could lead to the ‘inactivation’ of penicillin. (W) (Challenging) o Ensure the discussion covers: mutations in genes lead to new proteins;

the new protein can be an enzyme; the enzyme can breakdown penicillin;

Online http://www.tufts.edu/med/apua/index.shtml http://www.antibioticresistance.org.uk

http://www.cellsalive.com/pen.htm

http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/penicill.htm

http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/penicill.htm

http://textbookofbacteriology.net/antimicrobial.html

http://textbookofbacteriology.net/antimicrobial.html

http://www.tufts.edu/med/apua/index.shtml

http://www.tufts.edu/med/apua/index.shtml

http://www.antibioticresistance.org.uk/


V3.1 78


Key concepts DNA, the molecule of heredity, Natural selection, Organisms in their environment

hence antibiotic resistance. o Introduce beta lactamase (formerly penicillinase) as the enzyme. o Mention that plasmids often carry genes for antibiotic resistance.

Learners suggest how new proteins could act in other ways to provide resistance, e.g. membrane proteins pumping out antibiotics (efflux pumps) or inactivating them. (W) (Challenging)

Learners recall why it is important to complete a course of antibiotics in the treatment of TB. o Discuss how the presence of antibiotic acts as a selection pressure, so

resistant bacteria (with a mutation) are selected for, and those that are killed are selected against.

o Explain the different ways (vertical and horizontal transmission) that resistance can be passed. (W) (Challenging)

Learners write a summary of the discussions. (F)

Note

Two common errors: stating that resistance to the antibiotic develops in people, not in bacteria; confusing resistance with immunity.

/ http://www.s-cool.co.uk/a-level/biology/evolution/revise-it/evolution-in-action http://textbookofbacteriology.net/resantimicrobial.html Textbooks/Publications Bio Factsheet 100: Antibiotics and antibiotic resistance Bio Factsheet 71: The control of bacteria. Past Papers Paper 22, June 2011, Q4 (c)(d)

10.2.c discuss the consequences of antibiotic resistance and the steps that can be taken to reduce its impact Key concepts Natural selection, Organisms in their environment, Observation and experiment

Learners cover this learning objective by researching a chosen bacterium that shows multiple drug resistance and present their findings to the rest of the group. o Points to consider in reducing impact: dosage; length of treatment; use of

narrow spectrum antibiotics; identify correctly the causative organism; hygiene and aseptic conditions in areas such as hospitals; measures to reduce the impact of antibiotic therapy with farm animals. (W) (I) (H) (Challenging)

11.1.d explain the meaning of the term immune response, making reference to the terms antigen, self and non-self Key concepts

Learners suggest mechanisms considered as ‘first line of defence’ (e.g. skin, stomach acid). o Explain that the next defence will be responses to invasion of body tissue. o Discuss how the body can distinguish between non-self and self and recall

previous work on antigens. (W) (Basic)

Learners write a definition of antigen, referring to self and non-self, the production of specific antibody to form an antigen-antibody complex and

Past Papers Paper 21, Nov 2011, Q6 (c)

http://www.antibioticresistance.org.uk/

http://www.s-cool.co.uk/a-level/biology/evolution/revise-it/evolution-in-action



http://textbookofbacteriology.net/resantimicrobial.html

http://textbookofbacteriology.net/resantimicrobial.html


V3.1 79


Cells as the units of life including examples (e.g. a molecule on the outside of a bacterium, virus, parasite, allergen or tumour cell). (I) (Basic)

Discuss the meaning of immune response (a complex series of reactions of the body, involving white blood cells, to a non-self antigen) before learners make notes. (W) (I) (Challenging) o Ensure learners understand that the non-specific (innate) response

involves phagocytes and the specific (adaptive) response involves lymphocytes, and that the responses interact.

o Explain that the reactions result in destruction of the foreign invader and prepare the body for a faster response to a second invasion (so the person will have few or no symptoms).

11.1.a state that phagocytes (macrophages and neutrophils) have their origin in bone marrow and describe their mode of action Key concepts Cells as the units of life

Remind learners that all blood cells have their origin in the bone marrow (Unit 3, 5.1.c): stem cells) and that some mature elsewhere in the body. o Learners recall that monocytes mature into macrophages, which are

phagocytes (see Note 8.1.d, Unit 4). (W) (Basic)

Learners draw annotated labelled diagrams of a neutrophil, a monocyte, and a macrophage (arrow pointing from monocyte). Learners include a label to (Fc) receptors that can bind to antibodies. (I) (Basic)

Explain that phagocytes can respond to isolated pathogens or to antibodies bound to antigens of pathogens. (W) (Basic)

Learners sequence and label diagrams (provided by you) showing events occurring during phagocytosis, recalling studies on endocytosis, the role of receptors and function of lysosomes. o Learners should know the term antigen presenting cell (APC). (I) (Basic)

(Challenging)

Learners match cards of descriptive text (provided by you) to diagrams of stages. (F)

Learners compare and contrast phagocytes and lymphocytes on microscope slides. (I) (Basic)

CD-ROM Bioscope – has relevant images. Online http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab6/Lab6.htm http://micro.magnet.fsu.edu/index.html http://library.med.utah.edu/WebPath/HISTHTML/EM/EM001.html http://library.med.utah.edu/WebPath/HISTHTML/EM/EM002.html http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__phagocytosis.html Textbooks/Publications King p.164-165 Siddiqui p.181-182 Past Papers Paper 21, Nov 2011, Q6









http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__phagocytosis.html





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Paper 22, Nov 2011, Q2 (a)

11.1.b describe the modes of action of B-lymphocytes and T-lymphocytes Key concepts Cells as the units of life

Discuss how the non-specific response of phagocytes to infection differs from the specific response of B-lymphocytes and T-lymphocytes, which each have different modes of action. (W) (Basic)

Using a step-by-step teacher-prompted approach or by individual research, learners draw an annotated flow diagram to show how specific B-lymphocytes respond (humoral response): o Recognition and binding of specific antigen. o Activation/sensitisation followed by clonal expansion (mitotic division). o Differentiation to produce (i) plasma cells that make antibodies in a

primary immune response and (ii) memory cells (see 11.1.e). o There are important interactions with the T-lymphocytes response. (I)

(Challenging)

Discuss the similarity of the T-lymphocyte response (cell-mediated immunity) to the humoral response, before outlining other key points. o T-helper cells activation produces a clone of cells that release cytokines,

which stimulate and strengthen both the humoral response and macrophage response.

o T-killer (cytotoxic) cells activation produces a clone of cells that can directly kill, for example, infected cells.

o Both types produce memory cells. (W) (Basic)

Learners choose to show the information in a flow diagram or with written notes. (I) (Challenging)

Distinguish between receptors of B-lymphocytes and T-lymphocytes that bind non-self antigen: for B-lymphocytes the receptor is immunoglobulin (slightly different to a secreted antibody); the T-receptor recognises antigens displayed on the surface of APCs (see T-helper cells) or infected or foreign cells (see T-killer cells). (W) (Challenging)

Extension: learners research the effect of active HIV in human T-lymphocytes (also attacks phagocytes) and see the consequences of a reduction in numbers of white blood cells (helps to explain why people with HIV/AIDS are prone to opportunistic infections). (I) (Challenging)

Note

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/B_and_Tcells.html http://www.merckmanuals.com/home/immune_disorders/biology_of_the_immune_system/acquired_immunity.html?qt=immune%20response&alt=sh http://www.cellsalive.com/antibody.htm http://library.med.utah.edu/WebPath/HEMEHTML/HEMEIDX.html http://www.bu.edu/histology/p/21001ooa.htm Past Papers Paper 23, Nov 2013, Q.1 (b) Paper 21, Nov 2011, Q6 (c)

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/B_and_Tcells.html



http://www.merckmanuals.com/home/immune_disorders/biology_of_the_immune_system/acquired_immunity.html?qt=immune%20response&alt=sh




http://www.cellsalive.com/antibody.htm

http://www.cellsalive.com/antibody.htm

http://library.med.utah.edu/WebPath/HEMEHTML/HEMEIDX.html

http://library.med.utah.edu/WebPath/HEMEHTML/HEMEIDX.html

http://www.bu.edu/histology/p/21001ooa.htm



V3.1 81


Refer to humoral and cell-mediated responses (not required knowledge) as learners will see these terms in resources used.

11.1.e can be incorporated into this learning objective.

11.1.e explain the role of memory cells in long-term immunity Key concepts Cells as the units of life

Discuss why the presence of memory cells means that a secondary immune response will be faster and stronger than a primary response. (W) (Basic)

Learners suggest meanings for the term immunity and write out an agreed explanation of immunity and long-term immunity.

Learners could draw and annotate a sketch graph showing antibody concentrations against time during an immune response. (I) (Basic) o Learners reproduce this graph at a later date, with more detailed

annotations. (F)

Note

Encourage use of scientific terminology and explanations: phrases such as ‘remembers the disease’ and ‘fights the disease’ are unacceptable.

Online http://www.biology.arizona.edu/immunology/tutorials/immunology/09t.html

11.1.c describe and explain the significance of the increase in white blood cell count in humans with infectious diseases and leukaemias Key concepts Cells as the units of life

Provide learners with information about leukaemias. Learners write an account explaining the difference between an increase in white blood cell count accompanying infectious diseases with that of leukaemias. (F)

Learners explain why people with leukaemia are susceptible to infections. (I) (Basic)

Extension: learners research the difference between acute and chronic leukaemias. (H) (Challenging)

Online http://www.lls.org/diseaseinformation/managingyourcancer/newlydiagnosed/understandingdiagnosis/labimagingtests/bloodtests/bloodcounts/ Textbooks/Publications Siddiqui p.182-183

11.1.f explain, with reference to myasthenia gravis, that the immune system sometimes fails to distinguish between self and non-self Key concepts Cells as the units of life

Use myasthenia gravis as an example to explain what is meant by autoimmune disease, provide learners with a straightforward information sheet from which they can make their own bullet-pointed notes. (I) (Basic)

Extension: learners research other auto immune diseases to highlight the range of immune dysfunctions that can exist. (H)

Online http://www.nlm.nih.gov/medlineplus/ency/article/000816.htm https://www.mga-charity.org/information-mg

http://www.biology.arizona.edu/immunology/tutorials/immunology/09t.html

http://www.biology.arizona.edu/immunology/tutorials/immunology/09t.html

http://www.lls.org/diseaseinformation/managingyourcancer/newlydiagnosed/understandingdiagnosis/labimagingtests/bloodtests/bloodcounts/




http://www.nlm.nih.gov/medlineplus/ency/article/000816.htm

http://www.nlm.nih.gov/medlineplus/ency/article/000816.htm

https://www.mga-charity.org/information-mg

https://www.mga-charity.org/information-mg


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11.2.a relate the molecular structure of antibodies to their functions (see 2.3.b) Key concepts Biochemical processes

Revise protein structure with a short written test. (F)

Discuss the basic structure of an immunoglobulin (e.g. IgG) and how these molecules interact with antigens. (W) (Basic)

Explain that the variable regions in different antibodies have different sequences of amino acids and ask for suggestions as to how this related to the specificity of antibodies. (W) (Basic)

Learners use, for example, a ribbon diagram of IgG to explain how primary, secondary, tertiary and quaternary structures of proteins are shown. (P) (I) (Challenging)

Learners draw a labelled, annotated diagram linking the structure of an antibody to its function, reproducing this diagram at a later stage. (I) (F) (Challenging)

Note

Learners may be interested to know that antibodies are glycoproteins.

Mention the different antibody classes and refer to the term antitoxins (not required learning) for interest.

There is potential confusion between antibodies and antibiotics – apply error-free learning.

Online http://www.biology.arizona.edu/immunology/tutorials/antibody/structure.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AntigenReceptors.html Past Papers Paper 21, June 2013, Q2 Paper 23, Nov 2013, Q1

11.2.b outline the hybridoma method for the production of monoclonal antibodies Key concepts DNA, the molecule of heredity, Observation and experiment

Learners review antigens, antibodies, specificity, B-lymphocytes, plasma cells and cancer cells with a brainstorming session. (W) (Basic) (Challenging)

With guidance, learners work through the hybridoma method and produce either a summary flow diagram, set of notes, or completed table. Learners highlight the main stages of the process and the steps that occur within each stage are described and explained. (I) (Challenging)

Ask learners to state the desirable features which are contributed by each cell that become incorporated into the hybridoma cell (this contains the genetic material of both cells). (W) (Basic)

Learners describe the distinction between the hybridoma cell and the monoclonal antibody (see Note). (W) (Challenging)

Learners could make a list of all the cells involved in the production and state the role of each. (I) (Basic)

Discuss why there has been a move to produce humanised antibody rather than mouse antibody. (W) (Challenging)

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Monoclonals.html http://www.bio.davidson.edu/Courses/molbio/MolLearners/01rakarnik/mab.html http://www.nap.edu/openbook.php?record_id=9450&page=8 Past papers Paper 41, June 2012, Q2

http://www.biology.arizona.edu/immunology/tutorials/antibody/structure.html



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AntigenReceptors.html



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Monoclonals.html



http://www.bio.davidson.edu/Courses/molbio/MolStudents/01rakarnik/mab.html



http://www.nap.edu/openbook.php?record_id=9450&page=8

http://www.nap.edu/openbook.php?record_id=9450&page=8


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Note

Ensure learners understand that: o a clone (group of genetically identical cells formed from one original

‘ancestor’ cell) of hybridoma cells produces one type of specific antibody, monoclonal antibody;

o the ‘ancestor’ cell forms from the fusion of a specific plasma cell (B-lymphocyte) and a myeloma cell.

In this rapidly-developing area of biotechnology, learners need to apply biological principles and concepts to new situations.

11.2.c outline the use of monoclonal antibodies in the diagnosis of disease and in the treatment of disease Key concepts Observation and experiment

Explain that a sample of fluid taken from a person with an infectious disease could contain both pathogen (with non-self antigens) and specific antibody. (W) (Basic)

Learners study a set of diagrams showing the steps occurring in a direct enzyme-linked immunosorbent test (ELISA) and answer a set of questions that require application of the principles of immune response and knowledge of monoclonal antibody. (I) (Challenging) o Extension: learners describe what is occurring in an indirect ELISA test for

the presence of circulating specific antibody. (I) (Challenging)

Learners research one example of the use of monoclonal antibody in the treatment of disease and present their findings to the class. (H) (W) (Basic) (Challenging)

Note

Learners do not need to know the term ELISA or the details of the test.

Online http://www.mayoclinic.com/health/monoclonalantibody/CA00082 http://www.hhmi.org/biointeractive/immunology/vlab.html. http://web.archive.org/web/20080329002645/http://www.molecular-plant-biotechnology.info/hybridoma-and-monoclonal-antibodies-mabs/uses-of-monoclonal-antibodies.htm http://www.sumanasinc.com/webcontent/animations/content/pregtest.html Textbooks/Publications Bio Factsheet 112: Monoclonal antibodies Bio Factsheet 219: Monoclonal antibodies: An update Past papers Paper 41, June 2012, Q2 (b)(c)

11.2.d distinguish between active and passive, natural and artificial

Discuss the principles behind passive immunity before learners produce an account explaining why (i) passive immunity is immediate but short-lived and active immunity is delayed but longer-term, and (ii) passive immunity does

Online http://www.polioeradication.org/ http://www.who.int/features/factfiles/p

http://www.mayoclinic.com/health/monoclonalantibody/CA00082

http://www.mayoclinic.com/health/monoclonalantibody/CA00082

http://www.hhmi.org/biointeractive/immunology/vlab.html

http://www.hhmi.org/biointeractive/immunology/vlab.html

http://web.archive.org/web/20080329002645/http:/www.molecular-plant-biotechnology.info/hybridoma-and-monoclonal-antibodies-mabs/uses-of-monoclonal-antibodies.htm





http://www.sumanasinc.com/webcontent/animations/content/pregtest.html

http://www.sumanasinc.com/webcontent/animations/content/pregtest.html

http://www.polioeradication.org/

http://www.who.int/features/factfiles/polio/en/


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immunity and explain how vaccination can control disease Key concepts Cells as the units of life, Organisms in their environment, Observation and experiment

not produce memory cells whereas active immunity does. (W) (I) (Basic) (Challenging)

Learners draw an annotated version of the immune response curve to show how vaccines act to give immunity. (I) (Challenging)

Learners construct a summary chart, leaving enough room to add features and examples to show the differences between the categories, or, the chart of immunity is divided into active and passive, each divided into natural and artificial. (I) (Basic)

Discuss briefly how vaccination can provide immunity to avoid the spread of

disease. Include the term herd immunity. (W) (Basic)

Extension (highly relevant): learners access current information on the programme to eradicate polio.

olio/en/ Textbooks/Publications Bio Factsheet 99: Vaccines Bio Factsheet 71: The control of bacteria. Past Papers Paper 21, June 2011, Q6

11.2.e discuss the reasons why vaccination programmes have eradicated smallpox, but not measles, tuberculosis (TB), malaria or cholera Key concepts Cells as the units of life, Organisms in their environment

Discuss the features that contributed to the success of the smallpox vaccination programme, which was considered the main factor in the eradication of the disease. (W) (Basic) o Learners contribute information about the progress of vaccination

programmes for the other diseases. (W) (Basic)

Working in groups of four, each member researches one of the four named diseases, making comparisons with the smallpox vaccination programme. o Provide a list of terms to be incorporated into the group study, e.g.

antigenic concealment, antigenic drift, boosters, long/short-term, etc. (G) (Challenging)

Online http://www.who.int/features/2010/smallpox/en/ http://en.wikipedia.org/wiki/Ali_Maow_Maalin http://www.who.int/topics/vaccines/en/ http://www.s-cool.co.uk/a-level/biology/immunity/revise-it/problems-with-vaccines http://www.who.int/immunization/en/

Immunity

Natural

Active Passive

Artificial

Active Passive

http://www.who.int/features/factfiles/polio/en/

http://www.who.int/features/2010/smallpox/en/

http://www.who.int/features/2010/smallpox/en/

http://en.wikipedia.org/wiki/Ali_Maow_Maalin

http://en.wikipedia.org/wiki/Ali_Maow_Maalin

http://www.who.int/topics/vaccines/en/

http://www.who.int/topics/vaccines/en/

http://www.s-cool.co.uk/a-level/biology/immunity/revise-it/problems-with-vaccines



http://www.who.int/immunization/en/


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Past Papers Paper 22, Nov 2011, Q2 (b)(ii)(iii)


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Unit 6: The diversity of life


Learners should have a good understanding of the difference between plant and animal cells and of the difference between prokaryotes and eukaryotes from Unit 2. Also from Unit 2, learners should know the basic structure of viruses. They should also be familiar with ecological concepts, such as: the meaning of the terms population and community; the flow of energy through the different trophic levels of the ecosystem; and interactions between organisms. Context

This unit, above all the others, belongs to the learner. This is their opportunity to get to know the local environment, with opportunities for fieldwork and for research into local conservation issues and local conservation projects, allowing a practical application of the key concepts of organisms in their environment and of observation and experiment. Stimulating an interest in biodiversity will lead appropriately to the next unit, Unit 7, Genetics, population genetics and evolutionary processes. Outline

The unit begins with a discussion of the meaning of the terms species, ecosystem and niche so that learners will have a good grounding for later ecological studies, and then continues with a more detailed study of classification and taxonomy. Biodiversity is considered at three different levels, and species biodiversity is further explored by fieldwork opportunities in a local area. Spearman’s rank correlation and Pearson’s linear correlation, together with Simpson’s diversity of index are introduced as analytical tools for the data collected from fieldwork. The unit also covers the threats to the maintenance of biodiversity and discusses both issues concerning conservation and practical ways to conserve endangered species and restore degraded habitats. One aspect of the key concept of organisms in their environment is how humans can interact with their environment in ways that can have a great impact on ecosystems. Here, consideration is given to the part humans may play in the extinction of species. Teaching time



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18.1.a define the terms species, ecosystem and niche Key concepts Natural selection, Organisms in their environment

Carry out a brainstorming exercise to indicate how much learners can recall of each term. (W) (Basic)

Discuss the species concept (and difficulties in defining the term – there are over 20 definitions) before learners make notes. o Expand ideas of: reproductively isolated; production of fertile offspring;

members have the same (very similar) features in morphology, anatomy, physiology, behaviour and biochemistry; occupy the same niche; defined by same (very similar) DNA. (W) (I) (Basic)

Extension: learners explore difficulties in defining species in terms of fertile offspring by researching examples, e.g. between plant species or between mammalian species (polar bear and brown bear - rare; canid hybrids - common). (H) (Challenging)

Extension: learners consider how the species concept works for asexually reproducing organisms and for interspecific plasmid transfer between bacteria. (H) (Challenging)

Learners write a definition of an ecosystem, incorporating the following ideas and the same (or equivalent) terminology: (I) (Basic) o a self-sustaining unit consisting of abiotic and biotic factors interacting

together o includes all organisms of all populations (in a given area) o energy flows through and cycling of minerals occur.

Learners make notes on (ecological) niche, the functional role of a species, to include: a description of its habitat; how it is adapted to its environment; interactions with other organisms; features of its life-cycle. (I) (Basic)

Learners visit an ecosystem to place into context these terms and concepts, describing in terms of: energy flow / trophic levels; interactions between organisms; interactions between organisms and the physical environment. Examples of species and of niche are described. (G) (P) (Basic) (Challenging)

Explain that an ecosystem can vary in size and could be temporary or permanent. (W) (Basic)

Note

A niche is often described in terms of an organism or a population.

Online http://purchon.com/ecology/ http://www.ecologydictionary.org/ Textbooks/Publications Bio Factsheet 131: Ecological niche Past Papers Paper 22, June 2011, Q2 Paper 41, June 2012, Q1 (a)

http://purchon.com/ecology/

http://www.ecologydictionary.org/


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A field trip should be considered before covering 18.1.c) to 18.1.f). If a trip is not possible, visiting any suitable area populated by plants and animals, within or near to school, will be a rewarding experience for learners.

18.2.a describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family, genus and species Key concepts Cells as the units of life, DNA, the molecule of heredity

Learners suggest a method to sort all the different organisms in the world and then share ideas. (W) (G) (Basic)

Introduce the idea of sorting as ‘classification’ and agree that a hierarchical approach is sensible. o State that levels in the hierarchy are termed taxonomic ranks, with each

example of a rank known as a taxon (plural: taxa). o Explain that the members of a group share common (homologous)

features based on phylogenetic / evolutionary patterns (more details in Unit 7). (W) (Basic)

Display a ‘tree of life’ with the three domains and briefly outline the other taxonomic ranks, asking for suggestions why the species taxon is considered to be the only natural classification group. o Outline the classification of humans, with learners contributing their ideas.

(W) (Basic)

Learners note down the taxonomic ranks listed and decide a good mnemonic to help remember the hierarchical order. (P) (I) (Basic)

Extension: choose one or more organisms to classify from domain through to the species, for example, organisms encountered during fieldwork. (H) (Basic) (Challenging)

Extension: learners research classification systems based on analogous features. (I) (Basic)

Online http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artmay98/classif.html http://www.biologymad.com/master.html?http://www.biologymad.com/Classification/classification.htm Textbooks/Publications Bio Factsheet 91: Taxonomy and classification. Bio Factsheet 170: Answering Exam Questions: Classification and Keys

18.2.b outline the characteristic features of the three domains Archaea, Bacteria and Eukarya Key concepts Cells as the units of life, DNA, the molecule of heredity, Organisms in their environment

Learners complete a short written test (produced by you, with mark scheme) about prokaryotes and eukaryotes. (F)

Explain that the Archaea and Bacteria are both prokaryotic but have quite different features, reflecting their evolutionary history. o State some features of the Archaea that contrast with Bacteria: e.g.

different cell wall structure, which can be quite varied (not murein); different types of membrane lipids (not phospholipids); differences in tRNA and ribosomes.

o Discuss the specialised habitats of some members of the Archaea: high

Online http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Evolution/index.htm http://www.ucmp.berkeley.edu/alllife/threedomains.html

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artmay98/classif.html




http://www.biologymad.com/master.html?http://www.biologymad.com/Classification/classification.htm



http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Evolution/index.htm




http://www.ucmp.berkeley.edu/alllife/threedomains.html

http://www.ucmp.berkeley.edu/alllife/threedomains.html


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temperatures, extreme saline, and anaerobic environments. (W) (Basic)

Learners use resources (textbooks, internet, etc.) to produce a list of the main features of each domain. (I) (Basic)

Note For this syllabus learners should use ‘Bacteria’ and not ‘Monera’.

18.2.c outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia Key concepts Cells as the units of life, DNA, the molecule of heredity, Organisms in their environment

Learners brainstorm the names of the kingdoms. Write down all ideas so any incorrect can be put into context (i.e. see 18.2.a). o Agree the kingdoms and discuss criteria used for classification into Fungi,

Animalia or Plantae kingdom, e.g. animals are eukaryotic, multicellular, feed as heterotrophs. Point out that absent features also helps confirm the classification, e.g. no cells with cell walls, don’t photosynthesise.

o Discuss the Protoctista as the kingdom that contains organisms that do not quite fit into the other kingdoms.

o Learners make notes using resources. (W) (Basic)

Learners make up an imaginary ‘named’ organism and produce a sticky note or label with enough of a description for it to be classified into a kingdom. The notes could be stuck around the class for a class activity, learners revealing their answers at the end of the activity. (W) (I) (Basic) (Challenging).

Online http://www.ucmp.berkeley.edu/plants/plantae.html Textbooks/Publications Bio Factsheet 91: Taxonomy and classification Bio Factsheet 170: Answering Exam Questions: Classification and Keys Past Papers Paper 43, June 2011, Q1 (c) Paper 43, Nov 2011, Q1 (c) Paper 41, Nov 2012, Q11 (a)

18.2.d explain why viruses are not included in the three domain classification and outline how they are classified, limited to type of nucleic acid (RNA or DNA) and whether these are single stranded or double stranded Key concepts Cells as the units of life, DNA, the molecule of heredity

Check learner knowledge of the main features of viruses (1.2.f) with a question and answer session. o Add more information about the genetic material: either single or double-

stranded RNA or single or double-stranded DNA, but never both RNA and DNA.

o Learners produce a generalised diagram that is annotated. (W) (I) (Basic)

Learners suggest why viruses are not included in the three domain classification. o Remind learners of the Unit 2 discussion (viruses do not fit the key

concept of cells as the basic units of life) and see if they have any other points to contribute. (W) (Basic)

Online http://www.eoearth.org/view/article/51cbef267896bb431f69cb9a/?topic=51cbfc78f702fc2ba8129e70 http://www.johnkyrk.com/virus.html Textbooks/Publications Bio Factsheet 32: Viruses made simple.

18.1.b explain that biodiversity is considered

A discussion about the term biodiversity will highlight that a simple definition may be difficult. Introduce the idea of three different ‘levels’ of biodiversity,

Online http://www.eoearth.org/topics/view/49

http://www.ucmp.berkeley.edu/plants/plantae.html

http://www.ucmp.berkeley.edu/plants/plantae.html

http://www.eoearth.org/view/article/51cbef267896bb431f69cb9a/?topic=51cbfc78f702fc2ba8129e70



http://www.johnkyrk.com/virus.html

http://www.eoearth.org/topics/view/49480/


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at three different levels:

variation in ecosystems or habitats

the number of species and their relative abundance

genetic variation within each species

Key concepts DNA, the molecule of heredity, Organisms in their environment

ecosystem, species, and genetic. (W) (Challenging) o Point out the transition from an ecological to a molecular biological

approach. o Explain that ecosystem biodiversity is more difficult to measure, as

ecosystems may merge at their ‘boundaries’ (so not easy to define) and vary greatly in size.

Explain that biodiversity can be considered at a local, national and global level. (W) (Basic)

Give a definition of a habitat, for reference only, e.g. the particular location and type of local environment occupied by a population or organism, characterised by its physical features or by its dominant producers. (W) (Basic)

Learners volunteer the different types of medium-scale (meso) ecosystems in their region: e.g. wood/forest, lake/river, field, rocky shore (ecosystem biodiversity). o To understand how biodiversity can be reduced, learners suggest an

occurrence for each ecosystem that would lead to its loss. (W) (Basic)

In groups, volunteer states a habitat within one of the named ecosystems, choosing the next person to give another habitat and so on. (G) (Basic) (Challenging)

Reinforce, using examples, learner understanding of the differences between ecosystem and habitat, e.g. the habitat of a catfish is a freshwater stream versus the catfish is part of the freshwater ecosystem; removal of boulders from the stream bed reduces the variety/number of different habitats in the ecosystem. (W) (Basic)

Learners consider species biodiversity within a community. o Give a definition of community (reference only), e.g. all of the populations

of all of the different species within a specified area at a particular time. o Explain, using examples, the difference between number of species

(count of how many species exist within a particular community), and relative abundance of species (count how many members of each species there are - the population size).

o Expand the discussion to consider species diversity on a global scale. (W) (Challenging)

For genetic biodiversity, explain that a genome is the sum total of all the

480/ http://www.bbsrc.ac.uk/web/FILES/Exhibitions/pod2-factsheet.pdf http://www.geography.learnontheinternet.co.uk/topics/ecosystem.html http://wwf.panda.org/about_our_earth/biodiversity/what_is_biodiversity/ http://www.iucn.org/iyb/about/?gclid=CJ7n2a2576QCFQsGbAodI3nz1A


http://www.bbsrc.ac.uk/web/FILES/Exhibitions/pod2-factsheet.pdf


http://www.geography.learnontheinternet.co.uk/topics/ecosystem.html

http://www.geography.learnontheinternet.co.uk/topics/ecosystem.html

http://wwf.panda.org/about_our_earth/biodiversity/what_is_biodiversity/

http://wwf.panda.org/about_our_earth/biodiversity/what_is_biodiversity/

http://www.iucn.org/iyb/about/?gclid=CJ7n2a2576QCFQsGbAodI3nz1A

http://www.iucn.org/iyb/about/?gclid=CJ7n2a2576QCFQsGbAodI3nz1A


V3.1 91


hereditary information in an organism, and discuss how, although each species can be identified by a characteristic genome, there will still be variation (link to Unit 7). o Learners recall from Unit 3, the different nucleotide sequences for Hb

A

(normal) and HbS (sickle cell) alleles and their definition of a mutation

(6.2.b). o Explain that genetic biodiversity (variation) can be within a population or

between populations. (W) (Basic)

Learners summarise discussions with their own notes, using examples to help their explanation. (F)

Extension: learners consider further examples of how ecosystem biodiversity can be affected by different factors: trophic levels, food chains/webs and energy flow; the cycling of nutrients; interactions. (H) (Challenging)

Note When tackling variation in ecosystems or habitats, reference to some of the issues in 18.3.a and 18.3.h will help for later studies.

18.1.c explain the importance of random sampling in determining the biodiversity of an area Key concepts Organisms in their environment, Observation and experiment

Random sampling is best demonstrated by holding up one page from a large newspaper that contains words of different sized fonts, images and blank areas. o Explain that this simulates a field, which has no more than 26 species

living there, each species represented by a letter of the alphabet. (W) (Basic)

o Learners discuss a method to determine how many different species and how many individuals of each species there are (and only 30 minutes to carry out the task). (G) (Challenging)

o Discuss a suitable strategy, highlighting the importance of: having to sample; taking a number of samples (the sample may be unrepresentative, e.g. a photograph could represent a bare rock, so no individuals would be found); choosing the correct size/area of each sample; random sampling (biased sampling - any measurements can only apply to the sample, not to the whole area). (W) (Basic)

Note

Learning objectives 18.1.c to 18.1.f are best understood, and could be carried

Practical booklet 11 Online http://www.countrysideinfo.co.uk/howto.htm http://fua.field-studies-council.org/media/59629/how_to_carry_out_a_random_sample.pdf

http://www.countrysideinfo.co.uk/howto.htm


http://fua.field-studies-council.org/media/59629/how_to_carry_out_a_random_sample.pdf




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out, in the context of fieldwork. Practical booklet 11 may provide suitable protocols and should be consulted first.

18.1.d use suitable methods, such as frame quadrats, line transects, belt transects and mark-release-recapture, to assess the distribution and abundance of organisms in a local area Key concepts Organisms in their environment, Observation and experiment

See Note for 18.1.c.

Learners use resources to note the difference between distribution and abundance. (I) (Basic)

Discuss different techniques for estimating, e.g. counting numbers of each of the different species within the quadrat; ‘by eye’ estimation of percentage of quadrat covered by each particular plant species; using an abundance scale (e.g. ACFOR). o Learners suggest what to do with their data in order to make calculations

of estimates of population size. (W) (Basic)

Discuss how quadrats of a known area can be used for random sampling and the importance of: choosing the right size of frame quadrat (e.g. size of organisms, area to cover; reducing edge effects); when to use a quadrat with a grid. (W) (Basic)

Explain line and belt transects for systematic sampling. o Learners suggest advantages and disadvantages of belt versus line

transects. o Explain the difference between interrupted belt transects (quadrats placed

at regular intervals) or continuous belt transects (quadrats laid side by side). (W) (Basic)

Learners consider different (theoretical) fieldwork tasks and choose whether frame quadrats randomly placed, line transects, interrupted belt transects or continuous belt transects would be most the appropriate, justifying their answers. (H) (F) (Basic) (Challenging)

Discuss the concept behind the mark-release-recapture technique and situations where mark-release-recapture would be appropriate. Show the formula to use:

number in the first sample x number in second sample number marked in second sample

o Explain the problem if there is a low rate of recapture, e.g. 20 animals caught and marked, 1 marked in 10 captured the second time, estimate of total number =200/1 = 200, but 2 marked individuals recaptured makes the estimate only 100. (W) (Basic)

Practical booklet 11 Online http://www.countrysideinfo.co.uk/howto.htm http://fua.field-studies-council.org/media/59629/how_to_carry_out_a_random_sample.pdf http://fua.field-studies-council.org/teaching-equipment-and-methods.aspx http://www.biologymad.com/resources/RevisionM5Ch4.pdf http://www.nuffieldfoundation.org/applied-science/distribution-and-abundance-species Textbooks/Publications King Chapter 11 Siddiqui, Chapter 7 Bio Factsheet 5: An idiot’s guide to populations. Bio Factsheet 68: Fieldwork techniques Bio Factsheet 184: Investigating sand dunes.






http://fua.field-studies-council.org/teaching-equipment-and-methods.aspx



http://www.biologymad.com/resources/RevisionM5Ch4.pdf

http://www.biologymad.com/resources/RevisionM5Ch4.pdf

http://www.nuffieldfoundation.org/applied-science/distribution-and-abundance-species




V3.1 93


o Learners practise this using a container of beans or beads. Remove a small handful to be marked for the first sample, add them back to the container (shake them up), remove a second sample for the ‘recapture’ (closed eyes) and record results, obtaining the estimate using the formula. (P) (I) (Basic)

Learners obtain estimates of population size from several different sets of data using the mark-release-recapture formula. (I) (Basic) o Learners extract the required numerical data from paragraphs of prose to

estimate the population size (no formula provided). (F)

Learners make notes on the mark-release-recapture technique, annotating the formula to use and explaining some of the assumptions made: marked animals returned to the population mix randomly; the marking had no effect (e.g. non-toxic, more visible to predators); the marking remained on individuals; equal chance of capturing marked and unmarked individuals; no immigration or emigration during the sampling. (I) (Challenging)

Learners carry out fieldwork, using each of the methods listed to assess the distribution and abundance of organisms. (G) (P) (Basic) (Challenging)

18.1.e use Spearman’s rank correlation and Pearson’s linear correlation to analyse the relationships between the distribution and abundance of species and abiotic or biotic factors Key concepts Organisms in their environment, Observation and experiment


Discuss instances in fieldwork where differences in species abundance or distribution occurred (or provide examples). Explain that the next step is to find out if these correlate with some factor, either biotic or abiotic (see 18.1.a). o Explain the measure of association between two variables ranges from

completely negatively correlated, -1, to completely positively correlated, +1; the closer to these values, the stronger the relationship.

o Explain that a statistical test cannot confirm a relationship between the two, but can lends support to it. (W) (Basic)

Discuss situations when Pearson’s linear coefficient calculation is carried out: when there is interval (quantitative) data that shows a linear relationship and a statistical assessment of the strength of the correlation is required (e.g. data plotted on a scattergraph; a ‘by-eye’ judgment of correlation is not always reliable). (W) (Challenging) o Learners work through an example, with guidance, starting with a null

hypothesis statement before using the formula to calculate the Pearson product moment correlation. Learners use a table of critical values to

Practical booklet 11 Online http://www.statstutor.ac.uk/topics/correlation/pearsons-correlation-coefficient/ http://www.statstutor.ac.uk/topics/correlation/spearmans-correlation-coefficient/ http://www.heckgrammar.co.uk/index.php?p=10310 Textbooks/Publications Bio Factsheet 144: Spearman’s rank correlation coefficient.

http://www.statstutor.ac.uk/topics/correlation/pearsons-correlation-coefficient/



http://www.statstutor.ac.uk/topics/correlation/spearmans-correlation-coefficient/



http://www.heckgrammar.co.uk/index.php?p=10310

http://www.heckgrammar.co.uk/index.php?p=10310


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reject or accept the null hypothesis and make a statistically valid statement about the strength of the correlation and its significance. (W) (I) (Basic) (Challenging)

Explain that if one variable increases and the other increases (or decreases) then Spearman’s rank correlation can be carried out, even if the relationship is non-linear, and that ordinal data can also be used with this test. (W) (Challenging) o Work through examples with learners, as with Pearson’s test, and discuss

how to use Spearman’s table. (W) (I) (Basic) (Challenging)

Learners analyse relationships by practising a number of different examples using either Spearman’s rank correlation or Pearson’s linear correlation. o Learners then work with calculated values to analyse the data and make

judgements about the strength of the relationship. (I) (Basic) (Challenging)

Discuss how correlation does not imply causation, e.g. abundance of a plant species appears to decrease with increasing altitude. Applying caution with cause and effect would consider other factors that change with altitude (oxygen concentration, temperature, soil nutrients etc.). (W) (Basic)

Note

Learners should work through examples themselves before using other resources available to them.

Learners could use spreadsheet software to enter the relevant figures and obtain a scattergraph and the final calculated value, and then explain what the results are showing. You could set up spreadsheets of data for learners to access (see learning resources).

Practical booklet 11 includes the chi-squared test for association. This is another use in addition to the ‘goodness of fit’ test (see 16.2.d).

18.1.f use Simpson’s Index of Diversity (D) to calculate the biodiversity of a

habitat, using the formula D = 1–

(Σ(n/N)2) and state the significance of

different values of D


Explain that Simpson’s Index of Diversity gives an overall measure of diversity by taking into account the number of different species in a sample and the abundance of each species. o Explain that a high D value represents high biodiversity, indicating a high

number of species, evenly spread for abundance. The value of D goes

Practical booklet 11 Online http://www.countrysideinfo.co.uk/simpsons.htm http://www.nuffieldfoundation.org/applied-science/ecology-and-simpsons-

http://www.countrysideinfo.co.uk/simpsons.htm

http://www.countrysideinfo.co.uk/simpsons.htm

http://www.nuffieldfoundation.org/applied-science/ecology-and-simpsons-diversity-index



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Key concepts Organisms in their environment, Observation and experiment

down if there are fewer species, or if, for example, one or a few species are very abundant and others are very rare.

o Discuss how this can be used to compare biodiversity over time in any one area. (W) (Basic)

Learners use their fieldwork data (or be given data) to calculate a biodiversity value and state its significance. (I) (Challenging)

diversity-index Textbooks/Publications Bio Factsheet 34: Species diversity

18.3.a discuss the threats to the biodiversity of aquatic and terrestrial ecosystems (see 18.1 b) Key concepts Organisms in their environment, Observation and experiment

To check understanding of the terms, learners give examples of specific local terrestrial and aquatic ecosystems. (W) (Basic)

Discuss the global food and energy demands (from increasing population size, developing nations and increasing industrialisation) that may affect ecosystems (also to a lesser extent, demand for ‘living’ space). (W) (Basic) o Learners consider these factors on a local basis, suggest ways to satisfy

these demands and consider the consequential effects of this action on one chosen local terrestrial or aquatic ecosystem. (P) (Challenging)

o Point out that global effects, such as climate change and global warming can still affect at a local level. (W) (Basic)

o Learners add their ideas to master sheets headed, ‘demand for food’, ‘demand for energy’ and ‘demand for living space’ (each sheet divided vertically into ‘terrestrial ecosystems’ and ‘aquatic ecosystems’) and follow up with a class discussion. It is highly likely that their ideas will reflect what is happening globally. (W) (Basic)

Learners produce a general list, using local and global examples to help explain each point. (H) (Challenging)

Note

The effect of introducing alien species into an ecosystem is also an important feature, covered in 18.3.f (you may prefer to teach 18.3.f with 18.3.a).

Online http://evolution.berkeley.edu/evolibrary/news/120301_chipmunks http://www.wri.org/resources/maps http://www.iucnredlist.org/initiatives/freshwater/panafrica/threats http://www.biodiv.be/biodiversity/threats http://environment.nationalgeographic.co.uk/environment/ Textbooks/Publications Bio Factsheet 27: Biological effect of deforestation Bio Factsheet 203: Climate change and ecological decoupling Bio Factsheet 197: Biology of coral reef ecosystems Past Papers Paper 41, June 2011, Q8 (a)(b)

17.3.e explain why organisms become extinct, with reference to climate change, competition, habitat loss and killing by humans

Discuss what is meant by extinction, pointing out that it is a natural process and part of the theory of evolution by natural selection (see Unit 7). o Explain that there is a threshold number below which extinction is

inevitable. o Learners suggest why species become extinct (check that those

referenced in 17.3.e are covered). (W) (Basic)

Online http://www.bbc.co.uk/lastchancetosee/sites/about/extinction.shtml http://www.iucnredlist.org/ Past Papers


http://evolution.berkeley.edu/evolibrary/news/120301_chipmunks

http://evolution.berkeley.edu/evolibrary/news/120301_chipmunks

http://www.wri.org/resources/maps

http://www.iucnredlist.org/initiatives/freshwater/panafrica/threats

http://www.iucnredlist.org/initiatives/freshwater/panafrica/threats

http://www.biodiv.be/biodiversity/threats

http://www.biodiv.be/biodiversity/threats

http://environment.nationalgeographic.co.uk/environment/

http://environment.nationalgeographic.co.uk/environment/

http://www.bbc.co.uk/lastchancetosee/sites/about/extinction.shtml

http://www.bbc.co.uk/lastchancetosee/sites/about/extinction.shtml

http://www.iucnredlist.org/


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Key concepts Natural selection, Observation and experiment

Learners find examples (relevant to them) of plant and animal species that have become extinct or are near extinction for the reasons listed in 17.3.e and produce poster displays. (G) (P) (Basic)

Paper 43, June 2011, Q1 (a)

18.3.b discuss the reasons for the need to maintain biodiversity Key concepts Organisms in their environment, Observation and experiment

Learners research the reasons to maintain biodiversity. (H) (Basic) o In a follow-up discussion include the following ideas: maintenance of gene

pools; preservation of genetic diversity; applications of the use of gene technology (see Unit 8); current and new uses of organisms; discovery of new species (may have use in the future); aesthetic and spiritual benefits; practical value of animals (e.g. dolphins helping autistic children); the awe of the vast range of organisms, their attractive or unusual appearances and different methods of survival. (W) (Basic)

Agree some main categories, e.g. genetic, future uses, current uses, spiritual / aesthetic, etc. (W) (Basic) o Learners place each idea on the list in the correct category, with an

accompanying explanation. (I) (Challenging)

Online http://www.nationalgeographic.com/xpeditions/lessons/08/g68/preserve.html http://www.davidsuzuki.org/search/?q=biodiversity&x=0&y=0 http://wwf.panda.org/about_our_earth/biodiversity/biodiversity/ Textbooks/Publications Bio Factsheet 224: Why we need biodiversity Past Papers Paper 41, June 2012, Q6 (b)(ii) Paper 41, June 2013, Q9 (a) Paper 43, Nov 2013, Q5 (a)(iii)

18.3.g discuss the roles of non-governmental organisations, such as the World Wide Fund for Nature (WWF) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), in local and global conservation Key concepts Organisms in their environment, Observation and experiment

Learners suggest what is meant by ‘NGOs’. Discuss the advantages of non-governmental organisations, such as greater cooperation between nations, international agreements that can be reached sooner than inter-governmental agreements. o Introduce WWF and CITES. o Learners are shown or browse CITES Appendices I, II and III. (W) (Basic)

Learners check the websites or read summary print-out sheets to become familiar with a variety of NGOs active in conservation. o Agree a definition for the term ‘conservation’. (W) (Basic) o Learners write a short account summarising the role of the WWF and

CITES and the benefits of NGOs in general. They could also add details of a local conservation group. (H) (Basic)

Online http://wwf.panda.org/ http://www.cites.org/

http://www.nationalgeographic.com/xpeditions/lessons/08/g68/preserve.html



http://www.davidsuzuki.org/search/?q=biodiversity&x=0&y=0

http://www.davidsuzuki.org/search/?q=biodiversity&x=0&y=0

http://wwf.panda.org/about_our_earth/biodiversity/biodiversity/

http://wwf.panda.org/about_our_earth/biodiversity/biodiversity/

http://wwf.panda.org/

http://www.cites.org/


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18.3.c discuss methods of protecting endangered species, including the roles of zoos, botanic gardens, conserved areas (national parks and marine parks), ‘frozen zoos’ and seed banks Key concepts Organisms in their environment, Observation and experiment

Introduce the International Union for Conservation of Nature (IUCN). Discuss what is meant by the term ‘endangered’ (refer learners to work on biodiversity). o Discuss (or display the IUCN web page) the criteria used to classify an

organism as endangered. (W) (Basic) o Learners write a definition of the term ‘endangered’, researching a named

example and include the species name and the reasons for it being endangered. (H) (Basic)

o Learners findings are shared in a class presentation. (W) (Basic)

Learners refer to the species identified in their fieldwork for 18.1.d and use the IUCN Red List to determine their category. (I) (Basic)

Discuss what is meant by a frozen zoo and a seed bank. (W) (Basic) o Learners research the variety of methods employed to help protect

endangered species in one of: zoos, botanic gardens, national parks, marine parks. Include any advantages or disadvantages of each method. (G) (Basic) (Challenging)

o Learners produce a summary sheet of their research to share with the class. (W) (G) (Challenging)

o Produce one card for each member of the group. On each card write one of the categories listed (zoo, national park etc.). Give out the cards randomly. Learners give a written outline of methods used to protect endangered species. (F)

Learners research local and national efforts to protect endangered named species. (H) (Basic)

With reference to genetic improvement and the maintenance of the gene pool, learners research examples of wild relatives of crop plants, landraces of crop plants and rare breeds of livestock. (H) (Basic)

A visit to a national park, nature reserve, zoo or botanic garden will enable learners to see the work that is being done locally or nationally.

Note

Point out that the IUCN list does not cover all groups of organisms.

Online http://www.iucn.org/knowledge/tools/ http://www.iucnredlist.org/ https://worldwildlife.org/species/directory?direction=desc&sort=extinction_status http://www.kew.org/index.htm http://www.zsl.org/conservation/ http://www.petermaas.nl/extinct/index.html http://www.eoearth.org/topics/view/49513/ http://www.sandiegozooglobal.org/what_we_do_banking_genetic_resources/frozen_zoo/ http://animals.nationalgeographic.co.uk/animals/conservation/ Textbooks/Publications Bio Factsheet 65: Conservation Bio Factsheet 208: Captive breeding and the role of zoos Past Papers Paper 43, Nov 2011, Q1 (a)(b) Paper 42, June 2012, Q6 (a)

18.3.d discuss methods of assisted

Explain that humans can assist reproduction in endangered mammals and, with learner input, discuss the techniques involved.

Online http://users.rcn.com/jkimball.ma.ultra

http://www.iucn.org/knowledge/tools/

http://www.iucnredlist.org/

https://worldwildlife.org/species/directory?direction=desc&sort=extinction_status



http://www.kew.org/index.htm

http://www.zsl.org/conservation/

http://www.petermaas.nl/extinct/index.html

http://www.petermaas.nl/extinct/index.html



http://www.sandiegozooglobal.org/what_we_do_banking_genetic_resources/frozen_zoo/



http://animals.nationalgeographic.co.uk/animals/conservation/

http://animals.nationalgeographic.co.uk/animals/conservation/

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Sexual_Reproduction.html#ART


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reproduction, including IVF, embryo transfer and surrogacy, used in the conservation of endangered mammals Key concepts Organisms in their environment, Observation and experiment

o Learners suggest the considerations when deciding that assisted reproduction should be used, such as: research to decide on appropriate method (not always easy to study reproduction in rare mammals); modify technique to be specific to the mammal; evaluating success. (W) (Basic)

Learners make notes, using resources, outlining the main stages and the main principles involved. (I) (Challenging) o Learners apply the principles to examples they have been given or have

researched. (H) (Basic)

Learners could be asked to sort statements, some irrelevant to be discarded, to end up with a set of notes that could be used as a summary of assisted reproduction. (I) (Basic)

Note

Learners may have included ideas from this in their research for 18.3.c.

Although this learning objective is about endangered mammals, not about assisted reproduction for humans, the techniques are similar and learners may gain useful information by researching them.

net/BiologyPages/S/Sexual_Reproduction.html#ART http://www.eplantscience.com/index/biotechnology/animal_biotechnology/manipulation_of_reproduction_and_transgenic_animals/biotech_in_vitro_fertilization_technology.php http://nationalzoo.si.edu/SCBI/reproductivescience/consendangeredcats/ Textbooks/Publications Bio Factsheet 105: Manipulation and control of reproduction. Some parts of this are relevant. Past Papers Paper 41, June 2011, Q3 (a) Paper 42, June 2013, Q5

18.3.e discuss the use of culling and contraceptive methods to prevent overpopulation of protected and non-protected species Key concepts Organisms in their environment, Observation and experiment

Ensure learners know what is meant by the two terms, and then explain that there are frequently debates about the issue, including deciding when a population is considered to be ‘over-populated’. (W) (Basic)

Learners research examples meaningful to them, including the different reasons given to either culling or use of contraceptive methods, and explaining why one method was favoured. (I) (Basic)

Provide new examples: learners write a short article weighing up the advantages and disadvantages of culling versus contraceptive methods. (F)

Organise a mini debate. (W) (H) (Basic) (Challenging)

Note

Stress that learners will need to develop the ability to apply principles to new situations

Online http://www.egzac.org/whyusecontraception.aspx http://www.ceru.up.ac.za/elephant/faqs.php Textbooks/Publications Bio Factsheet 65: Conservation.

18.3.f use examples to explain the reasons for controlling alien species

Discuss how, in many ecosystems throughout the world, the introduction of alien species has had harmful economic or ecological effects (termed ‘alien-invasive’ species). Balance this with a discussion of how some alien species

Online http://www.birdlife.org/worldwide/programmes/invasive-alien-species



http://www.eplantscience.com/index/biotechnology/animal_biotechnology/manipulation_of_reproduction_and_transgenic_animals/biotech_in_vitro_fertilization_technology.php





http://nationalzoo.si.edu/SCBI/reproductivescience/consendangeredcats/

http://nationalzoo.si.edu/SCBI/reproductivescience/consendangeredcats/

http://www.egzac.org/whyusecontraception.aspx

http://www.egzac.org/whyusecontraception.aspx

http://www.ceru.up.ac.za/elephant/faqs.php

http://www.ceru.up.ac.za/elephant/faqs.php

http://www.birdlife.org/worldwide/programmes/invasive-alien-species

http://www.birdlife.org/worldwide/programmes/invasive-alien-species


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Key concepts Organisms in their environment, Observation and experiment

have been of benefit. (W) (Basic)

Learners research examples of alien species (local, national and global) that are now considered unwelcome, and for each explain the reasons for controlling them. (H) (Basic)

Note

This may have been discussed with 18.3.a.

Some agencies give ‘alien’ and ‘exotic’ slightly different meanings, others use them interchangeably. Also seen are ‘non-indigenous’, ‘non-native’ and ‘introduced’.

http://eol.org/info/460 http://www.galapagos.org/conservation/invasive-species/ Past papers Paper 41, June 2011, Q8 (a)(b)

18.3.h outline how degraded habitats may be restored with reference to local or regional examples Key concepts Organisms in their environment, Observation and experiment

Discuss the concept of restoration ecology and the need for scientific planning and understanding when restoring degraded habitats or ecosystems. (W) (Basic)

Learners research one example and present their findings to the group. (W) (I) (Challenging). Points to consider: o A description of the habitat before degradation. o Reasons for the degradation and what may happen if degradation

continues. o What could be / is being carried, with overall aims, e.g. re-establishing

what was, improving by addition of species or physical factors, modifying to create a new habitat.

o The benefits to the community of restoration.

Online http://en.wikipedia.org/wiki/Restoration_ecology http://www.ser.org/ http://www.nature.com/scitable/knowledge/library/restoration-ecology-13339059

http://eol.org/info/460

http://www.galapagos.org/conservation/invasive-species/

http://www.galapagos.org/conservation/invasive-species/

http://en.wikipedia.org/wiki/Restoration_ecology

http://en.wikipedia.org/wiki/Restoration_ecology

http://www.ser.org/

http://www.nature.com/scitable/knowledge/library/restoration-ecology-13339059




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Unit 7: Genetics, population genetics and evolutionary processes


Learners should have a good knowledge and understanding of the mitotic cell cycle from Unit 3. They should be able to describe the structure of DNA and the events occurring in DNA replication, in transcription and in translation from Unit 3, including an understanding of the genetic code. Learners should have a good understanding of what is meant by a gene, an allele and a gene mutation. An appreciation of the diversity of life, from Unit 6, will stimulate interest in how diversity has come about. Context

This unit builds on AS Level work, especially Unit 3, DNA and the mitotic cell cycle. It leads on from Unit 6, The diversity of life, so that learners are provided with an explanation of how the mechanisms of natural selection and isolation can lead to the formation of new species. This unit strongly incorporates the key concepts of cells as the basic units of life, biochemical processes, DNA, the molecule of heredity and observation and experiment. Knowledge and understanding gained in this unit will be particularly useful for Unit 8, Molecular biology and gene technology. Outline

The unit begins with an introduction to ideas and terms that will be needed. The mechanism and significance of meiosis is dealt with, showing how genetic information passes from parent to offspring. A link is made to gamete formation in animals and plants. Genetic crosses are practised and the chi-squared test is used. The nature of genes and alleles and their role in determining the phenotype is discussed, including human conditions that result from gene mutations. Once an understanding of basic genetics is gained, the unit leads to a consideration how the passage of information from parent to offspring is translated to population genetics. Variation, and its importance for the mechanism of natural selection, is studied before considering the role of natural selection in evolution and speciation. Natural selection is a key concept in biology, with mutation acting as the raw material for evolution. The unit considers how selection pressures allow successful individuals to survive to pass on genes to the next generation and how changes in the genetic make-up of the population, coinciding with isolation, can lead to speciation. The key concept of observation and experiment is exemplified by studying the improvement of the milk yield of dairy cattle and the improvement of crop plants by humans. Humans can apply the principles of natural selection to artificial selection and speed up the process of biological change. Teaching time



V3.1 101


16.1.a explain what is meant by homologous pairs of chromosomes Key concepts DNA, the molecule of heredity

Introduce the topic explaining that a fertilised egg cell will have a set of chromosomes from the mother and a set from the father, to give pairs of chromosomes in cells. (W) (Basic)

Discuss the features of homologous chromosomes. (W) (Basic) o Learners list the similarities and differences between a pair of homologous

chromosomes and note the differences between the X and Y chromosomes. (I) (Basic)

Note

Avoid using 46 chromosomes and 23 pairs of chromosomes in explanations (also for 16.1.b): a common error is stating these when answering questions about other organisms.

The term bivalent is the same as one pair of homologous chromosomes.

Online http://www.nature.com/nature/journal/v423/n6942/fig_tab/423810a_F1.html

16.1.b explain the meanings of the terms haploid and diploid and the need for a reduction division (meiosis) prior to fertilisation in sexual reproduction Key concepts Cells as the units of life, DNA, the molecule of heredity

From 16.1.a, explain that cells with one set of chromosomes are termed haploid (n), and a particular species has a specific haploid number. Extend this to explain the term diploid (2n). (W) (Basic) o Discuss why a diploid organism needs a reduction division (meiosis) to

produce haploid cells. Use phrases such as ‘restore the diploid number on fertilisation’, ‘to avoid doubling the number of chromosomes’. (W) (I) (Basic)

Extension: learners outline the differences between asexual and sexual reproduction and between asexual reproduction in eukaryotes and asexual reproduction in prokaryotes (background information - refer to binary fission). (H) (Challenging)

Note

Do not go into details of meiosis for this learning objective.

Mention that some organisms only have one set of chromosomes, while others have one set for some part of their life cycle

16.2.a (i) explain the terms gene, locus, allele, dominant, recessive, codominant, linkage, test cross, F1

Only part of this learning objective is included here: explain the terms gene, locus, allele, dominant, recessive, phenotype, genotype, homozygous and heterozygous

Learners recall previous studies:

Online http://www.biology.arizona.edu/vocabulary/mendelian_genetics/mendelian_genetics.html

http://www.nature.com/nature/journal/v423/n6942/fig_tab/423810a_F1.html

http://www.nature.com/nature/journal/v423/n6942/fig_tab/423810a_F1.html

http://www.biology.arizona.edu/vocabulary/mendelian_genetics/mendelian_genetics.html




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and F2, phenotype, genotype, homozygous and heterozygous Key concepts Biochemical processes, DNA, the molecule of heredity

gene 6.2.a definition allele 6.2.b concept of new alleles forming by mutation 6.2.c Hb

A and Hb

S alleles.

Use pipe cleaner or string models, with sticky labels for alleles, to help explain gene, allele, locus, dominant, recessive, heterozygous, homozygous, genotype, then discuss the meaning of phenotype. (W) (Basic)

Learners write definitions for the terms and draw diagrams of homologous chromosomes to annotate locus and allele and, using examples, draw homologous chromosomes with different genotypes (homozygous alleles and heterozygous alleles; dominant and recessive), indicating the phenotype. (I) (Challenging)

Learners match a set of cards with terms to a second set with definitions. (F)

Note

It is useful to introduce the term early so learners can correlate the behaviour of chromosomes in meiosis and the formation of gametes with allele behaviour (and enhance understanding of genetic crosses).

http://www.genome.gov/glossary/index.cfm?id=8 Textbooks/Publications Bio Factsheet 156: Dominant and Recessive Alleles. Bio Factsheet 45: Gene expression Past Papers Paper 41, Nov 2011, Q9 (a)

16.1.c outline the role of meiosis in gametogenesis in humans and in the formation of pollen grains and embryo sacs in flowering plants Key concepts Cells as the units of life

State that meiosis involves two divisions to produce four cells. Explain what is meant by the term ‘gamete’. Highlight the role of meiosis in terms of a reduction division and the production of genetically different cells. (W) (Basic)

Using resources, learners write out a definition and give an outline of gametogenesis, naming the ovary and testis as the organs involved and including the role of meiosis. (I) (Challenging)

Learners draw a fully labelled human life cycle. (I) (Basic)

Using resources and teacher input, learners produce annotated diagrams to outline the formation of pollen grains and embryo sacs. o Diploid pollen mother cells in pollen sacs (in the anther) divide by meiosis

to form 4 haploid microspores. These mature to become pollen grains (details of mitosis not required.

o In the ovule the megaspore mother cell divides by meiosis to form 4 haploid megaspores: one survives to divide by mitosis to produce an eight-nucleate embryo sac. (I) (Challenging)

Learners compare the main similarities and differences between gametogenesis in humans with pollen grain and embryo sac formation in plants.

Online http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__unique_features_of_meiosis.html http://highered.mcgraw-hill.com/sites/0072495855/learner_view0/chapter28/animation__spermatogenesis__quiz_1_.html Textbooks/Publications Bio Factsheet 168: Gamete Formation in Animals

http://www.genome.gov/glossary/index.cfm?id=8


http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__unique_features_of_meiosis.html




http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__spermatogenesis__quiz_1_.html





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o Include a flow chart diagram to highlight the stages where meiosis and mitosis occur. (H) (Challenging)

Note

Details of ovary and testis histology are not required.

Learners should be familiar with the terms oogenesis and spermatogenesis.

16.1.d describe, with the aid of photomicrographs and diagrams, the behaviour of chromosomes in plant and animal cells during meiosis, and the associated behaviour of the nuclear envelope, cell surface membrane and the spindle (names of the main stages are expected, but not the sub-divisions of prophase) Key concepts Cells as the units of life, DNA, the molecule of heredity

With a short written test (prepared by you, with mark scheme), assess learner recall of mitosis. (F)

Show learners diagrams or photographs of an ordered haploid chromosome set (karyotype), e.g. human sperm and egg to review knowledge of homologous chromosomes, haploid, diploid, sex chromosomes. (W) (Basic)

Learners model meiosis with teacher guidance. Use pipe cleaners (or string or wool) to demonstrate the behaviour of 4 chromosomes. Explain the use of e.g. one homologous pair (i.e. maternal and paternal) = 2 (sister chromatids) light blue and 2 dark blue pipe cleaners; the second homologous pair use a different colour, light and dark. o Learners model late interphase (DNA replication means 1 pipe cleaner

becomes 2 identical) before moving onto the stages of meiosis. Learners suggest ‘what happens next’ and explain why each stage occurs.

o At the appropriate points explain the concepts of chiasmata formation, crossing over and independent assortment. (P) (I) (Basic) (Challenging)

o Learners model meiosis (no help, noting the comparisons with mitosis (correct spellings). (P) (I) (Challenging)

Learners study prepared slides, photomicrographs and diagrams. (I) (Basic)

Learners draw a series of annotated diagrams, or annotate prepared diagrams. (I) (Basic)

Learners construct a table of differences between mitosis and meiosis or sort a set of statements into comparative statements, into two columns. (I) (Basic) (Challenging)

Online http://www.biologymad.com/CellDivision/CellDivision.htm www.biology.arizona.edu/cell_bio/tutorials/meiosis/page3.html http://www.biologyinmotion.com/cell_division/index.html http://www.sumanasinc.com/webcontent/animations/content/meiosis.html http://www.cellsalive.com/meiosis.htm Textbooks/Publications Bio Factsheet 50: Sources of genetic variation. Past Papers Paper 43, June 2011, Q7 (a)

16.1.e explain how crossing over and random assortment of homologous chromosomes during meiosis and random fusion of gametes at

Learners recall their understanding of a gene and an allele. Emphasise the importance of using the terms in the correct context. (W) (Basic)

Use the pipe cleaner models of a homologous pair (label ‘A’ on each chromatid of one homologue and label ‘a’ on each chromatid of the other) to explain how reduction division separates the two alleles of a gene.

Online http://www.biologymad.com/CellDivision/CellDivision.htm www.biology.arizona.edu/cell_bio/tutorials/meiosis/page3.html

http://www.biologymad.com/CellDivision/CellDivision.htm


http://www.biology.arizona.edu/cell_bio/tutorials/meiosis/page3.html


http://www.biologyinmotion.com/cell_division/index.html


http://www.sumanasinc.com/webcontent/animations/content/meiosis.html


http://www.cellsalive.com/meiosis.htm







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fertilisation lead to genetic variation including the expression of rare, recessive alleles Key concepts Cells as the units of life, DNA, the molecule of heredity

o Mention how this creates variation when gametes fuse randomly at fertilisation.

o Discuss how this allows rare recessive alleles to come together. (W) (Basic)

Choose two different organisms, e.g. fruit fly (n=4) and humans. Using 2n,

learners work out how many different types of gamete could be formed with two homologous pairs assorting randomly and independently at metaphase I of meiosis. (I) (Challenging)

Make a pipe cleaner / string model for a second homologous pair using ‘B’s and ‘b’s. Learners show how random assortment in one cell can produce AB and ab gametes, and in another Ab and aB gametes. o Using this example, learners explain how random fusion contributes to

variation. o Learners draw annotated diagrams to illustrate the concepts. (W)

(Challenging)

Add labels (‘alleles’) ‘D’ to the homologue with ‘A’ genes, and ‘d’ to the homologue with ‘a’ genes. Explain that if the genes are on the same chromosome, they are said to be linked. o Demonstrate crossing over to show how this can lead to even more

variation in the gametes (AD, ad = parental: Ad, aD = recombinant). o Explain that the longer the chromosome pair, the greater the number of

possible crossovers. o Learners draw annotated diagrams to illustrate the concept. (W)

(Challenging)

Learners give written and diagrammatic descriptions of random assortment, crossing over and random fusion, explaining how each of these leads to genetic variation. (F)

Note

Explain that homologous pairs assort randomly at metaphase I and this means they are assorting independently of other homologous pairs.

http://www.biologyinmotion.com/cell_division/index.html http://www.sumanasinc.com/webcontent/animations/content/meiosis.html http://www.cellsalive.com/meiosis.htm http://www.biozone.co.uk/biolinks/GENETICS.html#Inheritance http://www.contexo.info/DNA_Basics/Meiosis.htm http://www.sumanasinc.com/webcontent/animations/content/independentassortment.html Past Papers Paper 43, June 2011, Q7 (b)







http://www.biozone.co.uk/biolinks/GENETICS.html#Inheritance

http://www.biozone.co.uk/biolinks/GENETICS.html#Inheritance

http://www.contexo.info/DNA_Basics/Meiosis.htm

http://www.contexo.info/DNA_Basics/Meiosis.htm

http://www.sumanasinc.com/webcontent/animations/content/independentassortment.html




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16.2.a (ii) explain the terms gene, locus, allele, dominant, recessive, codominant, linkage, test cross, F1 and F2, phenotype, genotype, homozygous and heterozygous Key concepts Biochemical processes, DNA, the molecule of heredity

Only part of this learning objective is included here: explain the terms codominant, linkage, test cross, F1 and F2

Using the pipe cleaner / string models, discuss the meaning of the term codominant. (W) (Basic)

Remind learners of a simple monohybrid cross from previous studies and using the terms already discussed show what is meant by F1 and F2. Briefly explain a test cross for learners to define. (W) (I) (Basic)

Learners match a set of cards with terms from 16.2.a to a second set with all the definitions. (F)

Note

These definitions are best understood when tackling 16.2.b.

A full explanation of test cross should be reserved for later.

Online http://www.biology.arizona.edu/vocabulary/mendelian_genetics/mendelian_genetics.html http://www.genome.gov/glossary/index.cfm?id=8 Textbooks/Publications Bio Factsheet 156: Dominant and Recessive Alleles. Bio Factsheet 45: Gene expression







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16.2.b use genetic diagrams to solve problems involving monohybrid and dihybrid crosses, including those involving autosomal linkage, sex linkage, codominance, multiple alleles and gene interactions (the term epistasis does not need to be used; knowledge of the expected ratio for various types of epistasis is not required. The focus is on problem solving) Key concepts DNA, the molecule of heredity, Organisms in their environment, Observation and experiment

Using resources, learners write out what is meant by a monohybrid cross and a dihybrid cross, and explain what is meant by true (or pure) breeding, multiple alleles, pedigree diagrams, autosomal chromosome and sex chromosome. (I) (Basic)

Monohybrid cross: using a visual (photographs/drawings) simple example (e.g. purple and white flowers in pea plants), demonstrate how to set out a genetic diagram (circles should be drawn around the gametes). o Learners explain why they can be certain of the genotype if a pea plant

has white flowers. o Explain test crosses. (W) (Basic) o Learners work though one problem themselves and peer-check the quality

of the genetic diagrams. (I) (Basic)

Learners construct genetic diagrams, working through monohybrid cross problems, including pedigree diagrams. Learners also performing test crosses. (P) (I) (F) (Basic) (Challenging)

Codominance: describe an example of codominance and the convention to represent this (alleles as superscripts). Many examples involve a ‘colour’ gene: ensure learners know that C is for colour, not codominance. o Go through the different ratios obtained and ask learners to explain why

no test cross is required. (W) (Basic) o Learners work through some codominance problems (monohybrid

crosses). (I) (Basic) (Challenging)

Multiple alleles: as an example, discuss the inheritance of human blood groups (ABO system) to illustrate multiple alleles, dominance, recessiveness and codominance before learners work through problems. (W) (I) (Challenging) (Basic)

Sex linkage: describe the largely non-homologous X and Y chromosomes to explain why the male genotype has only one allele for genes located on sex chromosomes. o Using an example of a sex-linked trait, e.g. eye colour in Drosophila,

explain how to annotate the allele symbol as a superscript by the X (Y-

shows that the allele is absent in the Y chromosome). (W) (Basic) o Learners write down the possible genotypes for this trait, then tackle a

monohybrid cross problem, covering the reciprocal cross. (I) (Basic) o Emphasise that not all problems indicating numbers of individuals of each

Online http://learn.genetics.utah.edu/content/inheritance/ http://www.dnaftb.org http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.html http://faculty.baruch.cuny.edu/jwahlert/bio1003/genetics.html http://www.utilitypoultry.co.uk/sexlinkage.shtml http://udel.edu/~mcdonald/mythintro.html http://www.sumanasinc.com/webcontent/animations/content/mendel/mendel.html http://www.learnerstv.com/animation/animation.php?ani=2&cat=Biology Textbooks/Publications Bio Factsheet 23: Genetics made simple: I Bio Factsheet 97: A guide to sex linkage Bio Factsheet 93: The ABO Blood Group System Bio Factsheet 183: Variations from expected Mendelian Monohybrid Ratios. Bio Factsheet 115: Answering Examination Questions: Genetics Past Papers Paper 43, June 2011, Q9 (b) Paper 41, June 2012, Q7

http://learn.genetics.utah.edu/content/inheritance/



http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.html



http://faculty.baruch.cuny.edu/jwahlert/bio1003/genetics.html

http://faculty.baruch.cuny.edu/jwahlert/bio1003/genetics.html

http://www.utilitypoultry.co.uk/sexlinkage.shtml

http://www.utilitypoultry.co.uk/sexlinkage.shtml

http://udel.edu/~mcdonald/mythintro.html

http://udel.edu/~mcdonald/mythintro.html

http://www.sumanasinc.com/webcontent/animations/content/mendel/mendel.html






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sex, or stating ‘female crossed with male’ will be sex-linked inheritance. (W) (Basic)

o Learners state and explain the pattern of inheritance associated with sex-linkage and then practise questions. (I) (Challenging)

Learners model using pipe cleaners / string, or draw diagrams, to show how a written genetic cross correlates to events occurring at meiosis and fertilisation. (P) (I) (Challenging)

Dihybrid cross: explain that these involve two genes located on non-homologous chromosomes (unlinked / separate linkage groups). Work through a dihybrid cross, e.g. Mendel’s pea plants, showing how to write out genotypes e.g. AaBb and not ABab. (W) (Basic) o Learners work out the possible gametes from crossing the double

heterozygotes. Guide learners how to construct a Punnett square and complete it correctly before they work out the phenotypic ratio (explain that 9:3:3:1 still fits the 3:1 monohybrid crosses ratio: each gene shows a 12:4 ratio). Learners work through a test cross. (W) (I) (Challenging)

Linkage: remind learners of the concept of linkage and of crossing over (16.1.e)): two linked genes involve only one homologous chromosome pair. Using a model or diagrams, explain how linked genes could result in both parental and recombinant types in the gametes and offspring, but not in the standard Mendelian ratios. o Discuss why genes close together will produce few, if any, recombinant

types (the further apart the greater proportion of recombinant to parental types). (W) (Challenging)

Learners tackle a range of differentiated questions involving two genes. (I) (F) (Basic) (Challenging)

Note

The terms backcross and incomplete dominance are no longer used.

There are two approaches: (i) cover the theory of the learning objective, then learners work on genetics problems or (ii) have a set of problems prepared for each type of cross and learners practise these as they are taught.

Some human genetic traits used as examples in schools are now known to be more complex than at first thought, Learners should be discouraged from analysing patterns of inheritance in their family.


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16.2.c use genetic diagrams to solve problems involving test crosses Key concepts DNA, the molecule of heredity, Observation and experiment

This learning objective is covered in 16.2.b.

Consolidate by agreeing that a test cross should be performed to find out the genotype of an organism that is known to have a dominant trait but could be homozygous dominant or heterozygous. (W) (Basic)

Note Learners should appreciate the advantage of carrying out test crosses in terms of the ratios between the phenotypic classes when compared to a cross involving two heterozygotes.

Online http://learn.genetics.utah.edu/content/inheritance/ http://www.dnaftb.org

16.2.d use the chi-squared test to test the significance of differences between observed and expected results (the formula for the chi-squared test will be provided) (see Mathematical requirements) Key concepts Observation and experiment

Revise different ratios obtained with the different types of genetic cross, emphasising that these are theoretical (based on probability) ratios. o Learners mentally calculate expected numbers from totals e.g. with 40

offspring, how many of each if expecting a 3:1 ratio? (W) (Basic)

Approach the concept using observed results: learners suggest and justify the type of genetic cross when given actual genotype numbers, e.g. codominance, for a ratio of 32 red, 26 pink, 10 white flowers (ratio approximating 1:2:1). (W) (Basic) o Learners debate a result of: 15 red, 20 pink, 13 white. Agree that a

statistical test is needed to compare the observed ratio to the expected: near enough for differences to be due to chance effects or so different that other factors should be considered. (W) (Challenging)

Practical booklet 11. Work through, with guidance (if not covered in 18.1.e, in the context of field study), examples of the use of the chi-squared test. (I) (Basic)

Learners use a calculated chi-squared value to: o State the critical value at a stated probability level. o State where the chi-squared value fits in the range of probabilities. o Make a conclusion, referring to a null hypothesis and significance level. (I)

(Basic) (Challenging)

Learners use results from a genetic cross (increasing difficulty)to: o Practise the calculations involved in the chi-squared test o Interpret the results to write a valid conclusion about the nature of the

genetic cross. (I) (Basic) (Challenging) Note

See also the syllabus section, Mathematical requirements.

Online http://www.blc.arizona.edu/courses/mcb422/MendelStarFolder/merChiSquare.html Textbooks/Publications Bio Factsheet 79: The chi-squared test for goodness of fit. Past papers Paper 43, Nov 2013, Q1 Paper 51, Nov 2011, Q2 Paper 53, Nov 2011, Q2




http://www.blc.arizona.edu/courses/mcb422/MendelStarFolder/merChiSquare.html




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Learners should be able to: o Identify the situations where the use of the test is applicable o Use the table of critical values and state the probability of obtaining their

results by chance.

Learners should consider : o The use of stating the actual probability value (p), which they can

calculate using software o The probabilities of 0.05 and 0.01 (often used to report results).

17.1.a describe the differences between continuous and discontinuous variation and explain the genetic basis of continuous (many, additive genes control a characteristic) and discontinuous variation (one or few genes control a characteristic) (examples from 16.2.f) may be used to illustrate discontinuous variation; height and mass may be used as examples of continuous variation) Key concepts DNA, the molecule of heredity, Natural selection, Organisms in their environment

Explain that biological variation describes the variation within a population (members of the same species). o Learners suggest examples of variation that is: inherited / genetic; not

inherited / environmental; likely to be due to both genetic and environmental sources.

o Explain the equation Vp = Vg +Ve, (no need to learn) and use an example (e.g. blood groups) to show Ve = 0 when a trait is due only to genetic effects.

o Discuss the use of monozygotic twins, (Vg = 0), to study the effects of the environment on variation. (W) (Basic)

Learners produce a list of causes of genetic variation for sexually reproducing organisms and for asexually reproducing organisms (i.e. only mutation), as well as causes of environmental variation (disease, edaphic factors, climate, water availability, etc.). (I) (Challenging)

Using resources, learners define discontinuous variation (include a bar chart) and continuous variation (include a histogram), and give examples. (I) (Basic) o Learners consider a trait that has a genetic basis and describe what is

likely to be occurring to if the variation is (i) discontinuous (one/two genes), and (ii) continuous (polygenic, environmental effects may also contribute). (I) (Challenging)

Online http://www.nature.com/scitable/knowledge/library/mutations-are-the-raw-materials-of-evolution-17395346 http://www.nature.com/scitable/topicpage/genomics-enables-scientists-to-study-genetic-variability-6526364 http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/genes/genesrev1.shtml Textbooks/Publications Bio Factsheet 50: Sources of genetic variation

17.1.c use the t-test to compare the variation of two different populations (see Mathematical requirements)

Explain the situations where the t-test would be applicable and work through an example. (W) (Basic)

Learners work through a number of examples, stating a null hypothesis and using a table of critical values to state the probability of obtaining the result. (W) (I) (Basic) (Challenging)

Practical booklet 10 Online http://www.theseashore.org.uk/theseashore/Stats%20for%20twits/T%20T

http://www.nature.com/scitable/knowledge/library/mutations-are-the-raw-materials-of-evolution-17395346



http://www.nature.com/scitable/topicpage/genomics-enables-scientists-to-study-genetic-variability-6526364



http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/genes/genesrev1.shtml



http://www.theseashore.org.uk/theseashore/Stats%20for%20twits/T%20Test.html



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Key concepts Observation and experiment

Learners choose from a list of outlines of investigations those for which the t-test could be used. (F)

Note

There is information about this test in the syllabus (Mathematical requirements section).

Practical booklet 10 gives learners the opportunity to use the t-test on data that they have collected themselves

est.html http://archive.bio.ed.ac.uk/jdeacon/statistics/tress4a.html Textbooks/Publications Bio Factsheet 3: Which stats test should I use? Past papers Paper 51, June 2012, Q1 Paper 52, June 2011, Q2

17.1.b explain, with examples, how the environment may affect the phenotype of plants and animals Key concepts DNA, the molecule of heredity, Organisms in their environment

Learners recall the difference between genotype and phenotype and describe the flow of information from DNA to the phenotype. (W) (Basic)

Explain that the term ‘environment’ encompasses everything that is not considered genetic. (W) (Basic)

Learners research examples that they are given and provide explanations for the observations. (I) (Basic) (Challenging)

Learners research further examples and report back to the class. (H) (Basic)

Online http://www.flowersbulbs.com/ql_hydrangea_color.htm http://www.nature.com/scitable/topicpage/environmental-influences-on-gene-expression-536 http://www.nature.com/scitable/topicpage/phenotypic-range-of-gene-expression-environmental-influence-581 http://www.nature.com/scitable/content/gene-environment-interactions-from-epidemiological-studies-33011 http://www.newscientist.com/article/dn1520-iq-is-inherited-suggests-twin-study.html http://www.nature.com/scitable/topicpage/the-collective-set-of-alleles-in-a-6385985

16.2.e explain that gene mutation occurs by substitution, deletion and insertion of base pairs in DNA and outline how

Use questioning to gauge knowledge of DNA structure, the definition of a gene mutation, protein synthesis and protein structure. (W) (Basic)

Outline the changes that occur to give base substitution, deletion and insertion mutations. Point out how frameshift mutations arise. Learners can produce

Online http://www.dnaftb.org/dnaftb/27/concept/index.html http://www.who.int/genomics/public/g


http://archive.bio.ed.ac.uk/jdeacon/statistics/tress4a.html

http://archive.bio.ed.ac.uk/jdeacon/statistics/tress4a.html

http://www.flowersbulbs.com/ql_hydrangea_color.htm

http://www.flowersbulbs.com/ql_hydrangea_color.htm

http://www.nature.com/scitable/topicpage/environmental-influences-on-gene-expression-536



http://www.nature.com/scitable/topicpage/phenotypic-range-of-gene-expression-environmental-influence-581




http://www.nature.com/scitable/content/gene-environment-interactions-from-epidemiological-studies-33011



http://www.newscientist.com/article/dn1520-iq-is-inherited-suggests-twin-study.html



http://www.nature.com/scitable/topicpage/the-collective-set-of-alleles-in-a-6385985



http://www.dnaftb.org/dnaftb/27/concept/index.html

http://www.dnaftb.org/dnaftb/27/concept/index.html

http://www.who.int/genomics/public/geneticdiseases/en/index2.html


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such mutations may affect the phenotype Key concepts Biochemical processes, DNA, the molecule of heredity, Natural selection

summary notes. (W) (Basic) o Learners research and give an account of how a base substitution in the

Hb A

allele to produce the Hb S

allele leads to the altered amino acid in sickle cell anaemia. (W) (Challenging)

o Learners work out the new amino acid sequences for examples of insertion and deletion mutations and suggest how this could affect the protein synthesised (include examples leading to premature stop codons). (I) (Challenging)

Discuss how it is possible that some changes in DNA nucleotide sequences have no (e.g. same amino acid specified), or little (e.g. non-structural amino acid replaced) consequential effects while others have profound effects. (W) (Challenging)

Extension: learners research examples of gene mutations resulting in cystic fibrosis (differing severities). (W) (Challenging)

Note

Focus on gene mutation, but alert learners to the existence of chromosomal mutations (sections of chromosomes/many genes and chromosome number).

eneticdiseases/en/index2.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mutations.html Textbooks/Publications Bio Factsheet 94: Gene Mutations Bio Factsheet 179: Answering Exam Questions: Mutation Past Papers Paper 43, June 2011, Q9 (a)

16.2.f outline the effects of mutant alleles on the phenotype in the following human conditions: albinism, sickle cell anaemia, haemophilia and Huntington’s disease Key concepts DNA, the molecule of heredity, Organisms in their environment

Learners construct a flow chart to show how a gene mutation can lead to symptoms of sickle cell anaemia. (I) (Challenging)

Learners research one other condition from the list then work with others (that have covered the same condition) to produce an information sheet to present to the class to use as notes. (W) (G) (H) (Basic) (Challenging)

Online http://www.s-cool.co.uk/a-level/biology/evolution/revise-it/evolution-in-action Notes on sickle cell anaemia. Textbooks/Publications Bio Factsheet 110: Genetic Disease in Humans.

16.2.g explain the relationship between genes, enzymes and phenotype with respect to the gene for tyrosinase that is involved with the production of melanin

Provide information about the role of tyrosinase. Learners produce an annotated flow diagram to illustrate the relationship between the gene, the enzyme and the phenotype. (I) (Challenging)

Online http://ghr.nlm.nih.gov/gene/TYR

http://www.who.int/genomics/public/geneticdiseases/en/index2.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mutations.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mutations.html




http://ghr.nlm.nih.gov/gene/TYR


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Key concepts Biochemical processes, DNA, the molecule of heredity

17.1.d explain why genetic variation is important in selection Key concepts Natural selection

Discuss how named examples of animals, plants and bacteria with different genotypes and hence phenotypes (e.g. bacteria and antibiotic resistance) may differ in their chances of survival or in their reproductive capacity. (W) (Basic)

Learners suggest why ‘more likely to survive to reproduce’ is more important for the species than ‘more likely to survive’ (idea of passing on genetic information. (W) (Basic)

Learners debate the advantages and disadvantages of asexual and sexual reproduction. (G) (Basic)

Note Learners should have an outline of selection – covered in detail later.

Online http://learn.genetics.utah.edu/content/variation/sources/ http://darwiniana.org/evolution.htm http://www.eoearth.org/article/Genetic_variation http://www.wellcometreeoflife.org/ Past Papers Paper 43, Nov 2013, Q2 (c)

17.2.a explain that natural selection occurs as populations have the capacity to produce many offspring that compete for resources; in the ‘struggle for existence’ only the individuals that are best adapted survive to breed and pass on their alleles to the next generation Key concepts Natural selection

Introduce the idea that organisms have high reproductive potential and given ideal conditions, exponential or explosive population growth occurs (starting with a few individuals). o Describe examples of ideal conditions and for each ask learners to

suggest phenotypes (and hence genotypes) that are more likely to survive (introduce the term differential survival) if ideal conditions are not maintained.

o Remind learners of variation within a population and explain that some organisms are better adapted to survive when selection pressures act to control population size (most populations oscillate about a mean size).

o Explain that individuals that are better adapted to survive are said to be fitter than those who do not have the adaptations. (W) (Basic)

Learners list examples of selection pressures and describe phenotypes that are selected for and those selected against. (I) (Basic)

Learners summarise discussions with bullet-point notes and complete the idea of natural selection with the following points: o Individuals selected for pass on their alleles to their offspring when they

reproduce (differential reproduction) o The frequency of the allele in the population increases. (I) (Challenging)

Online http://www.bbsrc.ac.uk/web/FILES/Exhibitions/pod1-factsheet.pdf http://www.biologycorner.com/worksheets/peppermoth_paper.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Populations2.html http://www.eoearth.org/article/Population_ecology http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html www.biologyinmotion.com/evol/ http://anthro.palomar.edu/synthetic/synth_4.htm Past Papers Paper 43, June 2011, Q8

http://learn.genetics.utah.edu/content/variation/sources/

http://learn.genetics.utah.edu/content/variation/sources/

http://darwiniana.org/evolution.htm

http://www.eoearth.org/article/Genetic_variation

http://www.eoearth.org/article/Genetic_variation

http://www.wellcometreeoflife.org/



http://www.biologycorner.com/worksheets/peppermoth_paper.html

http://www.biologycorner.com/worksheets/peppermoth_paper.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Populations2.html



http://www.eoearth.org/article/Population_ecology

http://www.eoearth.org/article/Population_ecology

http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html


http://www.biologyinmotion.com/evol/

http://anthro.palomar.edu/synthetic/synth_4.htm



V3.1 113


Explain that a gene pool describes the sum of all alleles for all the genes in a population. (W) (Basic)

Explain that most mutations are not beneficial. Learners complete a worksheet (prepared by you) describing and explaining changes to allele frequencies / the gene pool following mutation: (a) if the mutation is not beneficial and is a (i) dominant allele and (ii) recessive allele; (b) if environmental factors change and the mutation becomes beneficial. (F)

Learners research examples of natural selection and produce a summary table: example, different phenotypes involved, selection pressure(s) involved, adaptation possessed, and additional notes. o Suggestions: warfarin resistance in rats; melanism in peppered moths;

cyanogenic clover; antibiotic resistance in bacteria; resistance in insects to insecticides. (H) (Challenging)

Learners choose one example from the summary table and write a sequential account to explain how allele frequencies within a population can change. (F)

Note

Avoid using the phrase ‘survival of the fittest’ (different phenotypes can be equally fit).

Background: take some time to discuss the work of Charles Darwin and Alfred Russel Wallace.

An understanding of abiotic and biotic limiting factors and of density-dependent and density-independent factors will be beneficial.

17.2.b explain, with examples, how environmental factors can act as stabilising, disruptive and directional forces of natural selection Key concepts Natural selection, Organisms in their environment

Explain that in most cases the environment remains relatively stable and so the same phenotype has a selective advantage in each generation.

Discuss how the environment acts as a stabilising force of natural selection, so that selection pressures act to remove the extremes of the phenotype (e.g. birth weight in human babies).

Discuss the other two modes of selection: directional, where allele frequencies change in one direction (e.g. drug resistance in bacteria) and disruptive, where the extremes of the phenotype are favoured (e.g. size of male Pacific salmon). (W) (Basic)

Learners draw annotated graphs for each of stabilising, directional and disruptive selection to show the frequency of phenotypes ‘before’, ‘during’ and ‘after’ a period of time when selection occurred. (I) (Basic)

Online http://www.eoearth.org/article/Evolution?topic=49508 http://www.blackwellpublishing.com/ridley/a-z/Stabilizing_selection.asp http://www.nature.com/nature/journal/v313/n5997/abs/313047a0.html Textbooks/Publications Bio Factsheet 44: Evolution. Also useful for 17.3c).

http://www.eoearth.org/article/Evolution?topic=49508

http://www.eoearth.org/article/Evolution?topic=49508

http://www.blackwellpublishing.com/ridley/a-z/Stabilizing_selection.asp

http://www.blackwellpublishing.com/ridley/a-z/Stabilizing_selection.asp

http://www.nature.com/nature/journal/v313/n5997/abs/313047a0.html

http://www.nature.com/nature/journal/v313/n5997/abs/313047a0.html


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Learners research and describe one further example for each of the three types. (H) (Challenging)

Past Papers Paper 42, June 2012, Q1 (a) Paper 42, June 2013, Q8 (b)

17.2.c explain how selection, the founder effect and genetic drift may affect allele frequencies in populations Key concepts Natural selection

Learners should consider how natural selection can affect the level of genetic variation for any one heritable trait. o Use an example (e.g. melanism in Biston betularia) to discuss how a

different set of selection pressures in a different environment affects allele frequencies and leads to different outcomes for the population. (W) (Basic)

Learners research the link between sickle cell anaemia and malaria to describe and explain the differences in allele frequencies between areas free of malaria and areas where malaria is endemic. (H) (Challenging)

Learners use beads to model the effect on allele frequency in a population by differential survival of two different genotypes for one gene. o Place a large (known) number of beads of two different colours (alleles) in

a container (the population). Decide on a percentage survival rate for the homozygous recessive genotype, e.g. 60%.

o Pick out pairs of beads at random, discarding four out of every ten pairs of recessive beads. When all beads have been used, only replace the ones which 'survived' (not discarded) and repeat for the next generation.

o Record numbers of each genotype in each generation and construct graphs to show the effect of selection over time. (G) (Challenging)

Introduce Darwin’s finches and outline the main points of the founder effect for learners to summarise. (W) (I) (Challenging)

Explain that genetic drift involves chance effects, known as sampling errors, where the allele frequencies of a small founding (ancestor) group are unlikely to be representative of the larger main population (the smaller the population the greater the likely effect). o Exemplify the concept using Darwin’s finches. (W) (Basic)

Learners suggest the similarities and differences between natural selection and genetic drift and then engage in class discussion. (W) (P) (Basic) (Challenging) o Similarities: both involve changes in allele frequency and can contribute to

change (evolution).

Online http://www.pbs.org/wgbh/evolution/library/06/3/l_063_03.html http://www.nature.com/scitable/knowledge/library/natural-selection-genetic-drift-and-gene-flow-15186648 http://biology4.wustl.edu/cloverproject/Assets/White%20Clover%20Background%20for%20Teachers.pdf http://evolution-textbook.org/content/free/notes/ch18_WN18Dc.html http://sickle.bwh.harvard.edu/malaria_sickle.html http://evolution.berkeley.edu/evolibrary/home.php Textbooks/Publications Bio Factsheet 191: What have we learned from Darwin’s finches?



http://www.nature.com/scitable/knowledge/library/natural-selection-genetic-drift-and-gene-flow-15186648




http://biology4.wustl.edu/cloverproject/Assets/White%20Clover%20Background%20for%20Teachers.pdf



http://evolution-textbook.org/content/free/notes/ch18_WN18D.html



http://sickle.bwh.harvard.edu/malaria_sickle.html

http://sickle.bwh.harvard.edu/malaria_sickle.html

http://evolution.berkeley.edu/evolibrary/home.php

http://evolution.berkeley.edu/evolibrary/home.php


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o Differences: natural selection is a directed process, genetic drift is not; only natural selection involves adaptations; with natural selection the frequency of the ‘advantageous’ allele increases whereas with genetic drift, allele frequencies change by chance/sampling error (the frequency of a ‘disadvantageous’ allele could increase). (W) (G) (Challenging)

17.2.d use the Hardy-Weinberg principle to calculate allele, genotype and phenotype frequencies in populations and explain situations when this principle does not apply Key concepts Natural selection, Observation and experiment

Explain that Hardy and Weinberg considered the behaviour of genes in idealised populations. o Work through an example to show how allele frequencies can be used to

calculate genotype frequencies and how genotype frequencies can be used to calculate allele frequencies. (W) (Basic)

o Learners work through simple examples using the Hardy-Weinberg equation and make notes. (I) (Basic)

Learners use an example where the number of individuals with the recessive trait is known to calculate the proportion, and hence number of, heterozygotes in a population. (W) (Challenging)

Learners make notes to: o Explain the differences between allele frequencies, genotype frequencies

and phenotype frequencies. o Explain the conditions that need to be met for the Hardy-Weinberg

principle to apply. (I) (Challenging)

Learners suggest reasons why an unchanging allele frequency from one generation to the next is rarely encountered in nature (non-random breeding; not all individuals produce offspring; not a static population as there is emigration/immigration; selection occurs; mutation occurs). o Discuss how these frequencies would change if mutations occurred (e.g.

harmful recessive mutations; heterozygote advantage etc.), so that learners appreciate the potential for change by evolution. (W) (Basic)

Explain to learners that the Hardy-Weinberg equations can be used to determine frequencies for ‘at this moment in time’ occurrences. o Learners use an example, e.g. the incidence of cystic fibrosis to calculate

the allele frequencies and work out the carrier frequency (the heterozygotes) in the population. (I) (Challenging)

Online http://anthro.palomar.edu/synthetic/synth_2.htm http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/Hardy_Weinberg.html http://highered.mcgraw-hill.com/sites/0767424263/student_view0/chapter4/the_hardy-weinberg_equilibrium.html# http://www.wwnorton.com/college/biology/discoverbio3/core/content/ch17/animations.asp http://www.perinatology.com/calculators/Hardy-Weinberg.htm Textbooks/Publications Bio Factsheet 211: Hardy Weinberg and population genetics.

17.3.a 17.3.c) includes the idea that species have formed from pre-existing species. Online



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/Hardy_Weinberg.html



http://highered.mcgraw-hill.com/sites/0767424263/student_view0/chapter4/the_hardy-weinberg_equilibrium.html




http://www.wwnorton.com/college/biology/discoverbio3/core/content/ch17/animations.asp



http://www.perinatology.com/calculators/Hardy-Weinberg.htm

http://www.perinatology.com/calculators/Hardy-Weinberg.htm


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state the general theory of evolution that organisms have changed over time Key concepts Natural selection

Discuss the ideas of ‘change over time’ and of common descent - there is overwhelming evidence to suggest that all life is related. (W) (Basic)

Learners research examples of evolution to outline how change over time has occurred. (H) (Challenging) o A class discussion will help learners appreciate that the pace of change

can be different for different examples.

http://evolution.berkeley.edu/evolibrary/article/evo_47 Textbooks/Publications Jones, Fosbery, Taylor, Gregory, pages 253-254 (2007), or pages 374-375 (2013), includes the Darwin-Wallace theory and a discussion about speciation.

17.3.b discuss the molecular evidence that reveals similarities between closely related organisms with reference to mitochondrial DNA and protein sequence data Key concepts Biochemical processes, DNA, the molecule of heredity, Natural selection

Learners suggest the type of evidence used to determine whether organisms were closely related (i.e. comparative morphology and anatomy, fossils, classification and embryology). (W) (Basic) o Explain how the continually improving techniques to obtain DNA

base/nucleotide sequences and protein amino acid sequences (e.g. rapid sequencing) has provided databases to improve understanding of relationships. (W) (Challenging)

Explain that evolutionary related proteins that belong in a group (protein family) can be most usefully compared between organisms. (W) (Basic)

Introduce the use of a single letter code for the amino acids before learners analyse (in terms of closely related organisms) sequence data of a number of organisms (e.g. for cytochrome C). (I) (Challenging)

With prompting, learners suggest how mitochondrial DNA differs from nuclear DNA (inherited only from the mother; doesn’t swap genetic material with paternal mitochondrial DNA and higher mutation rate). o Discuss the usefulness, in terms of close relationships, of databases for

comparing mitochondrial DNA sequences of different organisms. (W) (I) (Challenging)

Note

This has close links to 19.2.a) and bioinformatics.

Learners should understand that there are freely accessible databases available to researchers.

Online http://evolution.berkeley.edu/evolibrary/news/100501_xwoman http://www.wiley.com/college/pratt/0471393878/instructor/activities/phylogenetic_trees/index.html http://www.indiana.edu/~ensiweb/lessons/molb.ws.pdf Past papers Paper 43, Nov 2013, Q2

17.3.c Review learner understanding of the terms species and gene pool by a Online

http://evolution.berkeley.edu/evolibrary/article/evo_47

http://evolution.berkeley.edu/evolibrary/article/evo_47

http://evolution.berkeley.edu/evolibrary/news/100501_xwoman

http://evolution.berkeley.edu/evolibrary/news/100501_xwoman

http://www.wiley.com/college/pratt/0471393878/instructor/activities/phylogenetic_trees/index.html



http://www.indiana.edu/~ensiweb/lessons/molb.ws.pdf

http://www.indiana.edu/~ensiweb/lessons/molb.ws.pdf


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explain how speciation may occur as a result of geographical separation (allopatric speciation), and ecological and behavioural separation (sympatric speciation) Key concepts Natural selection, Observation and experiment

question and answer session. (W) (Basic)

Define speciation. o Discuss the importance in speciation of (i) reproductive isolation and (ii)

natural selection acting within a population in different ways on different groups. (W) (Basic)

Give examples (e.g. separating land masses millions of years ago and road laying dividing up forests) illustrating ways that sub-populations are formed by geographical separation and brainstorm other examples. (W) (Basic) o Discuss how the different abilities of organisms to move from one area to

another are an important factor in the formation of new species. o Remind learners that the process of allopatric speciation requires that the

populations remain separated and interbreeding is prevented. (W) (Basic)

Learners research one or two examples and use these to explain what is meant by allopatric speciation. (I) (Basic)

Extension: learners research how the observations made of the four species of mockingbirds in the Galapagos Islands are believed to have had a large influence on Darwin’s development of the concept of natural selection. (H) (Challenging)

Introduce the idea of sympatric speciation: occurring within the same geographic area by reducing gene flow between groups of the same population. o State that two of the many ways to do this is by ecological separation and

by behavioural separation and ask learners to suggest what this means or to volunteer examples. (W) (Basic)

o Learners research one example of each to explain the principles involved and share their findings with the group. (W) (I) (Challenging)

Learners research the evolution of cichlid fish in the great lakes of Africa, e.g. Lake Victoria, and present arguments as to whether speciation has occurred by allopatric speciation, sympatric speciation, or both. (I) (Challenging)

Learners continue their work on Darwin’s finches and the founder effect to explain how speciation has occurred by both allopatric and sympatric speciation. (I) (Challenging)

Learners write a paragraph comparing allopatric and sympatric speciation. (F)

http://people.rit.edu/rhrsbi/GalapagosPages/DarwinFinch.html http://www98.homepage.villanova.edu/robert.curry/Nesomimus/index.html http://www.sciencedaily.com/releases/2011/10/111003080523.htm http://www.the-scientist.com/?articles.view/articleNo/23704/title/Evidence-for-sympatric-speciation/ http://www.nature.com/scitable/topicpage/polyploidy-1552814 http://www.evolutionsbiologie.uni-konstanz.de/pdf1-182/P089.pdf http://evolution.berkeley.edu/evolibrary/news/090301_cichlidspeciation Textbooks/Publications Bio Factsheet 142: Modern Examples of Evolution in Action Bio Factsheet 92: Isolation Mechanisms Past Papers Paper 41, June 2011, Q8 (c) Paper 41, June 2012, Q1

17.3.d Remind learners that isolating mechanisms provide a barrier to gene flow and Online

http://people.rit.edu/rhrsbi/GalapagosPages/DarwinFinch.html

http://people.rit.edu/rhrsbi/GalapagosPages/DarwinFinch.html

http://www98.homepage.villanova.edu/robert.curry/Nesomimus/index.html

http://www98.homepage.villanova.edu/robert.curry/Nesomimus/index.html

http://www.sciencedaily.com/releases/2011/10/111003080523.htm

http://www.sciencedaily.com/releases/2011/10/111003080523.htm

http://www.the-scientist.com/?articles.view/articleNo/23704/title/Evidence-for-sympatric-speciation/




http://www.nature.com/scitable/topicpage/polyploidy-1552814

http://www.nature.com/scitable/topicpage/polyploidy-1552814

http://www.evolutionsbiologie.uni-konstanz.de/pdf1-182/P089.pdf

http://www.evolutionsbiologie.uni-konstanz.de/pdf1-182/P089.pdf

http://evolution.berkeley.edu/evolibrary/news/090301_cichlidspeciation

http://evolution.berkeley.edu/evolibrary/news/090301_cichlidspeciation


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explain the role of pre-zygotic and post-zygotic isolating mechanisms in the evolution of new species Key concepts Natural selection

when successful interbreeding no longer occurs a new species is considered to have been formed. (W) (Basic)

Learners write out definitions of the two types of reproductive isolating mechanisms and then decide whether the examples from 17.3.c are pre-zygotic or post-zygotic. (I) (Basic)

Post-zygotic isolating mechanisms may need further discussion and summary with individual notes. o Discuss what is meant by a hybrid (hybridisation from 17.2.f is a different

context). Explain that generally a hybrid dies as an embryo or is sterile if it survives, so a sub-population on the verge of becoming a separate species is unlikely with interbreeding to incorporate back into the main population – the gene pools are sufficiently different.

o Explain that hybrids that manage to produce fertile offspring tend to be less fit than others and with natural selection will die out. (W) (I) (Challenging)

Provide descriptive examples of speciation on separate cards for learners to produce two piles, pre-zygotic or post-zygotic and then compare with a partner. (P) (I) (Basic)

Learners produce a written outline of the overall role of isolating mechanisms in speciation and then describe, using examples, the contribution of pre-zygotic and post-zygotic isolating mechanisms. o The account should highlight the differences between the two. A word list

or a hints sheet could be provided. (F)

http://www.biologyaspoetry.com/terms/postzygotic_barrier.html Textbooks/Publications Bio Factsheet 92: Isolation Mechanisms Past papers Paper 43, Nov 2013, Q2 (c)

17.2.e describe how selective breeding (artificial selection) has been used to improve the milk yield of dairy cattle Key concepts Natural selection, Observation and experiment

Explain that in selective breeding, humans have applied knowledge of natural selection to make ‘improvements’. (W) (Basic)

Discuss why selective breeding to improve the milk yield of dairy cattle must take place over several generations. (W) (Basic) o Learners suggest main stages involved in the selective breeding

programme, before presenting ideas to the group. (W) (G) (Basic) o Learners research details, guided by prompts such as: ‘Explain whether

one or many genes are involved’; ‘State what needs to be considered for improved milk yield’; ‘Describe other desirable features for the cattle involved’. (H) (Challenging)

Learners describe (e.g. in a table) the similarities and differences between

Online http://www.ilri.org/InfoServ/Webpub/fulldocs/SmHDairy/chap5.html#Dairy%20cattle http://rstb.royalsocietypublishing.org/content/360/1459/1479.full#abstract-1 http://babcock.wisc.edu/node/182 http://www.petermaas.nl/extinct/articles/selectivebreeding.htm Textbooks/Publications

http://www.biologyaspoetry.com/terms/postzygotic_barrier.html

http://www.biologyaspoetry.com/terms/postzygotic_barrier.html

http://www.ilri.org/InfoServ/Webpub/fulldocs/SmHDairy/chap5.html#Dairy%20cattle



http://rstb.royalsocietypublishing.org/content/360/1459/1479.full#abstract-1



http://babcock.wisc.edu/node/182

http://www.petermaas.nl/extinct/articles/selectivebreeding.htm

http://www.petermaas.nl/extinct/articles/selectivebreeding.htm


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selective breeding and natural selection. (F)

Learners use data for milk yield of different generations in a selective breeding programme to carry out a statistical comparison (t-test). (I) (Challenging)

Learners discuss the balance between improving features and maintaining genetic diversity. (G) (Challenging)

Bio Factsheet 187: Selective Breeding of Cattle Past Papers Paper 43, Nov 2011, Q8

17.2.f outline the following examples of crop improvement by selective breeding:

the introduction of disease resistance to varieties of wheat and rice

the incorporation of mutant alleles for gibberellin synthesis into dwarf varieties so increasing yield by having a greater proportion of energy put into grain

inbreeding and hybridisation to produce vigorous, uniform varieties of maize


Continue the theme of 17.2.e with a discussion about the need to supply an increasing global population and the improvement of crop plants. o Learners suggest the most important crop plants grown (the three most

important are maize wheat and rice – grain crops). o Outline the difference between crop improvement by conventional means,

selective breeding, and improvement by genetic modification. (W) (Basic)

Learners may be able to name a disease to which wheat (e.g. stem rust) and rice (e.g. sheath blight) are susceptible; discuss the need to breed crop plants resistant to disease (e.g. disease lowers yield and some can leave harmful toxins in the crop). o Learners recall the steps involved in selective breeding and suggest

desirable features, e.g. resistant to infection, maintaining resistance for a long time, localising infection to one area of the plant, resistance to toxin accumulation, seed (kernel) resistance, able to produce a high yield when infected. (W) (Challenging)

o Learners research the steps involved in introducing disease resistance into wheat or rice (cover one crop each and share notes). (P) (Basic)

State that the presence of gibberellins leads to stem elongation and explanations will be covered in Unit 11 (15.2.d, 16.3.d). o Explain that the sd-1 gene encodes an enzyme (GA20-oxidase) involved

in the later stages of gibberellin biosynthesis. o Learners suggest an outcome if mutations in this gene occur (very low

levels of gibberellins resulting in dwarf varieties). o Explain that some varieties of crops such as rice and barley have these

semi-dwarf / dwarf varieties. (W) (Challenging)

Learners write definitions of inbreeding and hybridisation and explain what is meant by inbreeding depression, outbreeding, and hybrid vigour. (I) (Basic) o Discuss the difficulties in maize in achieving the balance between

homozygosity and heterozygosity. (W) (Basic)

Online http://archaeology.about.com/od/domestications/qt/wheat.htm http://www.dupont.com/corporate-functions/our-approach/global-challenges/food.html http://irri.org/our-work/research/better-rice-varieties/disease-and-pest-resistant-rice http://www.lsuagcenter.com/en/crops_livestock/crops/rice/Diseases/ http://www.agprofessional.com/resource-centers/wheat/disease/news/Do-disease-resistant-wheat-varieties-pay-a-price-in-yield-229754951.html http://www.businessinsider.com/10-crops-that-feed-the-world-2011-9?op=1 Past Papers Paper 43, June 2011, Q4 (a) Paper 41, Nov 2013, Q5

http://archaeology.about.com/od/domestications/qt/wheat.htm

http://archaeology.about.com/od/domestications/qt/wheat.htm

http://www.dupont.com/corporate-functions/our-approach/global-challenges/food.html



http://irri.org/our-work/research/better-rice-varieties/disease-and-pest-resistant-rice




http://www.lsuagcenter.com/en/crops_livestock/crops/rice/Diseases/

http://www.lsuagcenter.com/en/crops_livestock/crops/rice/Diseases/

http://www.agprofessional.com/resource-centers/wheat/disease/news/Do-disease-resistant-wheat-varieties-pay-a-price-in-yield-229754951.html




http://www.businessinsider.com/10-crops-that-feed-the-world-2011-9?op=1




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o Learners list the advantages and disadvantages of inbreeding and outbreeding in maize. (I) (Challenging)

o Learners explain how selective breeding has produced homozygous maize plants that can be crossed with other homozygous plants, to produce hybrids with combinations of desirable features. (I) (Challenging)

Extension: learners research the ‘Green Revolution’ and debate the advantages and disadvantages of this. (W) (Basic)


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Unit 8: Molecular biology and gene technology


The structure of proteins and the structure of DNA from Unit 1 should be well understood. In addition, from Unit 3, learners should be familiar with semi-conservative replication of DNA and understand the principles of transcription, the genetic code and translation in the synthesis of proteins. Knowledge from Unit 7 of gene expression, including an understanding of how some mutations affect gene expression is also required. Context

This unit provides learners with the opportunity to consider some of the latest developments in biology and appreciate the key concept of observation and experiment. In this unit, learners will see how humans can make use of living systems and organisms to benefit themselves, such as in the development of genetically modified plants and in improvements in genetic screening, in the treatment of genetic disorders and advancements in forensic science. Knowledge and understanding of biological facts, principles and concepts from previous units will help their understanding of the techniques applied. Outline

The lac operon is studied as an example of gene regulation and control in eukaryotes is touched upon with a discussion of the role of transcription factors. The study of gene expression with the use of microarrays is covered. Recombinant DNA is explained and steps involved in genetic engineering are covered, including the use of enzymes, plasmids, markers and control sequences, including promoters. Two main applications of genetic engineering, the production of proteins of medical importance and the production of genetically modified crops and livestock are studied. Gel electrophoresis and the amplification of DNA by the polymerase chain reaction are two techniques that are described and an application of these is considered with an outline of the technique associated with genetic fingerprinting. Learners see that the pace of development of genetic technology can be partly attributed to bioinformatics. Other aspects of genetic technology that are covered are the sequencing of genomes, screening for genetic conditions and gene therapy. The unit also includes a discussion on the social and ethical issues and implications of genetic technology. Teaching time



V3.1 122


16.3.b explain genetic control of protein production in a prokaryote using the lac operon Key concepts Biochemical processes, DNA, the molecule of heredity

Learners complete a short written test (prepared by you, with mark scheme) to remind them of previous knowledge and help understanding of this unit. o Include relevant questions on: prokaryote structure (including plasmids

and genes for antibiotic resistance); definition of a gene; DNA structure and replication; protein synthesis. (F)

o Go through the answers before proceeding. (W) (Basic)

Explain that in protein synthesis, gene expression describes the whole process where DNA is transcribed to produce mRNA, which is translated to produce polypeptides (that form proteins). o Discuss the need to control gene expression, as all genes cannot be

switched on at any one time. (W) (Basic)

Explain the concept of an operon, then display a diagram of the arrangement in the lac operon and describe the gene products of gene Z and gene Y.

o Discuss the roles of lactose permease and -galactosidase in lactose uptake and metabolism, encouraging learners to contribute using AS Level knowledge. (W) (Challenging)

Learners participate in a group demonstration using a large model set-up. o Sheets of coloured paper stuck together represent the operon (promoter,

operator, genes Z, Y and A); the operator gene has a shape cut out, complementary to the shape of the repressor protein; a separate sheet of paper represents the regulatory gene (located elsewhere on the genome); use different shapes for each of glucose, lactose, RNA polymerase and repressor protein.

o Discuss each gene and then place on top of them cards with their labels (remove to test learners).

o Involve learners to describe the state of the operon when: no lactose is present and glucose is present; when no glucose is present and lactose is present. (W) (Challenging)

o Repeat, but this time allow learners to take charge and share out the demonstration. (W) (I) (Challenging)

Learners annotate a set of diagrams and give explanations. (I) (Challenging)

Learners complete a gap-filling exercise that serves as their notes. (I) (Basic)

Learners sort out a set of statements to show the sequence of events occurring (F)

Online http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter12/animation_quiz_4.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LacOperon.html Textbooks/Publications Bio Factsheet 45: Gene Expression

http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html



http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter12/animation_quiz_4.html




http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LacOperon.html



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Note

The lac operon of Escherichia coli was the first example of genetic control discovered and investigated.

Details of cAMP and the catabolite activator protein are not required.

16.3.a distinguish between structural and regulatory genes and between repressible and inducible enzymes Key concepts Biochemical processes, DNA, the molecule of heredity

Learners make notes on the differences between: structural and regulatory genes; repressible and inducible enzymes. (I) (Basic) o Learners also explain that a repressor protein is the product of a

regulatory gene. o Learners determine whether the enzyme products of the lac operon

structural genes are repressible or inducible enzymes (they are inducible). (I) (Basic)

Online http://textbookofbacteriology.net/regulation.html http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter12/animation_quiz_4.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LacOperon.html

16.3.c explain the function of transcription factors in gene expression in eukaryotes Key concepts Biochemical processes, DNA, the molecule of heredity

Explain that RNA polymerase in eukaryotic cells cannot initiate transcription alone: binding of transcription factors (proteins) to the DNA and to each other allow RNA polymerase to bind; others bind to the RNA polymerase (the whole complex is termed the transcription initiation complex). (W) (Basic) o Learners draw annotated diagrams to visualise the function of

transcription factors. (I) (Basic)

Extension: learners investigate more detail of transcription factors, e.g. how inactive transcription factors can be activated. (I) (Challenging)

Online http://biotech.about.com/od/proteinengineering/f/transcriptfact.htm

19.1.i explain, in outline, how microarrays are used in the analysis of genomes and in detecting mRNA in studies of gene expression Key concepts DNA, the molecule of heredity,

Discuss how each cell of a multicellular organism contains the same genes, but some will be inactive and there will be no gene expression (link back to 16.3.b). o Learners suggest why detection of mRNA is carried out to measure gene

activity. (W) (Basic)

Explain, step-by-step, the principles behind the use of microarrays, with learners making notes.

Online http://www.bio.davidson.edu/courses/genomics/chip/chip.html http://www.genome.gov/glossary/index.cfm?id=125 http://www.web-books.com/MoBio/Free/Chap9.htm http://learn.genetics.utah.edu/content

http://textbookofbacteriology.net/regulation.html

http://textbookofbacteriology.net/regulation.html










http://biotech.about.com/od/proteinengineering/f/transcriptfact.htm

http://biotech.about.com/od/proteinengineering/f/transcriptfact.htm

http://www.bio.davidson.edu/courses/genomics/chip/chip.html

http://www.bio.davidson.edu/courses/genomics/chip/chip.html



http://www.web-books.com/MoBio/Free/Chap9.htm

http://www.web-books.com/MoBio/Free/Chap9.htm

http://learn.genetics.utah.edu/content/labs/microarray/


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Observation and experiment o Researchers can now access a database of nucleotide sequences (often called ‘gene sequences’) for different genes.

o Multiple copies of the sequences are placed by robotic machines (micro-scale process) into separate areas on a solid surface, e.g. glass slide.

o Using reverse transcriptase, cDNA is synthesised using fluorescent nucleotides from the mRNA collected, indirectly ‘labelling’ the genes that are most active.

o cDNA added to the microarray surface ‘hybridises’ (complementary copy) with their particular gene sequence.

o The intensity of the fluorescent-coloured areas can be detected using scanners and the most active genes identified. (W) (Challenging)

Discuss a use of microarrays for learners to research further, e.g. comparing gene activity of healthy and diseased cells. o E.g. use red fluorescent nucleotides to ‘label’ the cDNA of a healthy cell,

use green for that of the tumour cell. A combined image of the two scans will show red, green and yellow areas: red = genes from healthy cell expressed more than tumour cell; green = genes from the tumour cell expressed more; yellow = both cells expressing the genes equally. (W) (H) (Challenging)

/labs/microarray/

19.1.a define the term recombinant DNA Key concepts DNA, the molecule of heredity

Remind learners that, in Unit 7, ‘recombination’ and ‘recombinant’ are terms used in the context of crossing over and the production of genetically different gametes and offspring. (W) (Basic)

Explain that there are many definitions of recombinant DNA: learners need the idea that novel DNA is formed by joining together DNA/genes from different sources. o Explain that DNA can be added to plasmids, hence the term ‘recombinant

plasmid’, and transferred from one organism to another, hence ‘recombinant host’. (W) (Basic)

Learners write a definition, qualifying with reference to recombinant plasmids and recombinant hosts. (I) (Basic)

Online http://higheredbcs.wiley.com/legacy/college/voet/0470129301/animated_figs/ch03/3-26.html

http://learn.genetics.utah.edu/content/labs/microarray/

http://higheredbcs.wiley.com/legacy/college/voet/0470129301/animated_figs/ch03/3-26.html




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19.1.b explain that genetic engineering involves the extraction of genes from one organism, or the synthesis of genes, in order to place them in another organism (of the same or another species) such that the receiving organism expresses the gene product Key concepts DNA, the molecule of heredity, Observation and experiment

Remind learners that genes code for proteins and in genetic engineering the desired product is a protein. o Learners suggest why it is necessary to use another organism to produce

the protein. (W) (Basic)

Talk learners through the outline construction of a large flow diagram: brief explanations for each step will help for 19.1.c, 19.1.e, 19.1.f, 19.1.g and 19.1.h, when they can add further notes (see below). (W) (I) (Basic)

Learners suggest why mRNA is sometimes used to obtain the gene (many

more copies of the mRNA in the cell than the genes; a host bacterial cell cannot cut out introns from the RNA transcripts of eukaryotic DNA). (W) (Challenging)

Introduce the idea that DNA libraries are now available. (W) (Basic)

Explain that a vector (carrier) is frequently used (often a plasmid) to get the desired gene into the host. (W) (Basic) o Discuss when gene cloning occurs: producing many initial copies of the

desired gene and as the host cell replicates. (W) (Challenging)

Learners revise 17.2.a and give an account of the similarities and differences between genetic engineering and selective breeding. (H) (Challenging)

Learners investigate what is meant by a cDNA library. (I) (Challenging)

Note

19.1.b can be amalgamated with 19.1.h.

Online http://www.learner.org/interactives/dna/engineering.html http://www.biology.arizona.edu/molecular_bio/problem_sets/Recombinant_DNA_Technology/recombinant_dna.html

Textbooks/Publications Bio Factsheet 13: Genetic engineering Past Papers Paper 41, Nov 2011, Q7

Obtain desired gene, e.g. from one of:

Method to insert gene into host organism

Gene expressed in host organism

Harvest desired protein product

extract (‘cut out’) from donor

synthesise from mRNA extracted from donor

synthesise using genetic code (known amino acid

sequence or partial sequence and use a cDNA library)

http://www.learner.org/interactives/dna/engineering.html

http://www.learner.org/interactives/dna/engineering.html

http://www.biology.arizona.edu/molecular_bio/problem_sets/Recombinant_DNA_Technology/recombinant_dna.html





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19.1.h explain the roles of restriction endonucleases, reverse transcriptase and ligases in genetic engineering Key concepts Biochemical processes, Observation and experiment

Outline the role of restriction endonucleases and DNA ligases. o Explain how different endonucleases cleave at different, specific

sequences to obtain blunt or ‘sticky’ / overlapping ends. o Learners add the enzymes to their main flow-chart from 19.1.b and

annotate. (W) (Basic)

Provide learners with details of different restriction endonucleases. On nucleotide sequence diagrams, learners indicate the cleavage sites and state whether blunt or sticky ends are produced and the number of fragments formed. (P) (I) (Challenging)

Outline the role of reverse transcriptase. o Learners annotate their flow chart. o Explain where DNA polymerase would be required (amplifies the gene).

(W) (I) (Basic)

Learners sequence a set of cards, each containing a single step involved in genetic engineering. With a second set of cards containing more detail, allocate these to the correct step. (F)

Learners produce a summary table of names of enzymes involved in genetic engineering and details of the reactions they catalyse. (H) (Basic)

Extension: learners research the origins of these enzymes. (I) (Basic)

Online http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120078/bio37.swf::Restriction%20Endonucleases http://www.geogene.com/genetic-eng-basics.html Past Papers Paper 42, June 2012, Q4 (a)(i)

19.1.e describe the properties of plasmids that allow them to be used in gene cloning Key concepts Cells as the units of life, DNA, the molecule of heredity, Observation and experiment

Discuss features of plasmids and ask learners to suggest advantages: found in bacteria (will be taken up); small (easy to manipulate/easily taken up); replicate semi-conservatively (identical copies); replicate independently within bacteria (so gene cloning occurs); can be removed from one bacterial species and be taken up by another (greater flexibility); can be cut at specific locations by restriction endonucleases (for gene insertion). (W) (Challenging) o Learners add annotations in the relevant steps of their flow chart of 19.1.b.

(I) (Basic)

Explain that once bacteria have taken up the plasmid, they are said to be ‘transformed’. (W) (Basic)

Background: explain that plasmids are more easily taken using, for example, electroporation or by using calcium ions and heat shock (the bacteria are said to be ‘competent’). (W) (Basic)

Note

Online http://www.addgene.org/mol_bio_reference/plasmid_background/

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120078/bio37.swf::Restriction%20Endonucleases





http://www.geogene.com/genetic-eng-basics.html

http://www.geogene.com/genetic-eng-basics.html

http://www.addgene.org/mol_bio_reference/plasmid_background/

http://www.addgene.org/mol_bio_reference/plasmid_background/


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It is preferable to state that plasmids are taken up, rather than ‘placed in’ bacteria.

Learners should appreciate that other organisms, such as yeasts, are useful in genetic engineering, as they can carry plasmids.

19.1.f explain why promoters and other control sequences may have to be transferred as well as the desired gene Key concepts DNA, the molecule of heredity, Observation and experiment

Learners recall (16.3.b) that a promoter is a nucleotide sequence on the DNA where RNA polymerase attaches to initiate transcription. o Explain that the transcription start point (the first nucleotide to be

transcribed) is within the sequence and the promoter allows the RNA polymerase to recognise which DNA strand is the template.

o Remind learners of the involvement of transcription factors and that there are genes coding for these, and that other control sequences exist (no detail required). (W) (Basic)

With these discussed, learners suggest why, in genetic engineering, promoters and other control sequences may need to be transferred with the desired gene. (W) (Challenging)

Learners make brief annotations to their summary flow-chart from 19.1.b. (I) (Basic)

Learners write a short paragraph to explain the role of promoters and why they can be said to control the expression of a gene. (F)

Extension: learners investigate how the early production of insulin by genetic engineering used the machinery of the lac operon to control gene expression. (I) (Challenging)

Note

In bacteria, RNA polymerase recognises and binds to the promoter with the aid of one main protein transcription factor but in eukaryotes binding is enabled by a complex of transcription factors.

Online http://www.addgene.org/mol_bio_reference/promoter_background/ Past Papers Paper 42, June 2012, Q4 (a)(ii) Paper 41, June 2013, Q2 (c)(ii)

19.1.g explain the use of genes for fluorescent or easily stained substances as markers in gene technology

Learners recall the concepts involved in DNA uptake to produce recombinant hosts (19.1.b). o Explain that a cut plasmid may (with DNA ligase present) re-circularise

and be taken up by a host bacterial cell, or a bacterial cell may not be transformed (take up the plasmid). These bacteria would not have the desired gene.

Online http://www.dnaftb.org/34/problem.html http://www.chm.bris.ac.uk/motm/GFP/GFPh.htm http://www.conncoll.edu/ccacad/zim

http://www.addgene.org/mol_bio_reference/promoter_background/

http://www.addgene.org/mol_bio_reference/promoter_background/

http://www.dnaftb.org/34/problem.html

http://www.dnaftb.org/34/problem.html

http://www.chm.bris.ac.uk/motm/GFP/GFPh.htm

http://www.chm.bris.ac.uk/motm/GFP/GFPh.htm

http://www.conncoll.edu/ccacad/zimmer/GFP-ww/GFP-1.htm


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Key concepts DNA, the molecule of heredity, Observation and experiment

o Agree that some method to identify the recombinant bacteria is desirable (‘screening for recombinants’) in order to avoid wasting money if all bacterial forms were cultured together. (W) (Basic)

Use images to explain how the gene encoding GFP, green fluorescent protein (most commonly used gene), is placed between the promoter and the desired gene. Transcription of both genes occurs and GFP and the desired product result. o Discuss how UV light enables selection of host cells for large scale

culturing, while non-recombinant bacteria will not fluoresce. (W) (Challenging)

o Learners add annotations to their flow-chart from 19.1.b about screening for successful recombinants and write a paragraph of explanation. (I) (Challenging)

Learners research one example where genes for enzymes that produce fluorescent or easily stained substances are now used as markers. Examples are presented to the class. (W) (G) (P) (Basic)

Note

Background: provide learners with a brief historical perspective on the use of antibiotic resistance markers to enable screening and explain why these are becoming less favoured.

mer/GFP-ww/GFP-1.htm http://www.scholarpedia.org/article/Fluorescent_proteins http://www.microscopyu.com/articles/livecellimaging/fpintro.html http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fluorescentproteins/fluorescentproteinshome.html http://www.gmo-compass.org/eng/safety/human_health/126.position_efsa_antibiotic_resistance_markers.html http://www.medicalnewstoday.com/articles/31227.php Past Papers Paper 41, Nov 2012, Q3 (a)(ii) Paper 41, June 2013, Q2 (b)

19.2.c explain the advantages of producing human proteins by recombinant DNA techniques (reference should be made to some suitable examples, such as insulin, factor VIII for the treatment of haemophilia and adenosine deaminase for treating severe combined immunodeficiency (SCID)) Key concepts Cells as the units of life, Biochemical processes,

Discuss the advantages of producing human proteins by genetic engineering / recombinant DNA techniques (‘genetic manipulation’ is also a term used). o Discuss how some of the diseases were not previously treatable with the

natural protein: could not be extracted or produced (e.g. adenosine deaminase); expensive to produce and purify; required extraction from many blood donations (e.g. factor VIII); problems with the protein used for treatment (e.g. insulin from pigs or other mammals).

o Discuss additional benefits such as: fewer/no allergic responses from contaminants; lower/no immune responses from non-self antigen detection; no risk of disease from contaminating pathogens; ethically/religiously/morally more acceptable.

o Include an outline of the benefits of using bacteria, yeast or mammalian cells in tissue culture. (W) (Basic)

Learners research the genetically engineered protein products for treatment of

Online http://www.diabetes.co.uk/insulin/human-insulin.html http://resources.schoolscience.co.uk/unilever/16-18/proteins/Protch4pg3.html http://ghr.nlm.nih.gov/condition/adenosine-deaminase-deficiency Past Papers Paper 43, Nov 2011, Q5 (b)

http://www.conncoll.edu/ccacad/zimmer/GFP-ww/GFP-1.htm

http://www.scholarpedia.org/article/Fluorescent_proteins

http://www.scholarpedia.org/article/Fluorescent_proteins

http://www.microscopyu.com/articles/livecellimaging/fpintro.html

http://www.microscopyu.com/articles/livecellimaging/fpintro.html

http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fluorescentproteins/fluorescentproteinshome.html



http://www.gmo-compass.org/eng/safety/human_health/126.position_efsa_antibiotic_resistance_markers.html




http://www.medicalnewstoday.com/articles/31227.php

http://www.medicalnewstoday.com/articles/31227.php

http://www.diabetes.co.uk/insulin/human-insulin.html

http://www.diabetes.co.uk/insulin/human-insulin.html

http://resources.schoolscience.co.uk/unilever/16-18/proteins/Protch4pg3.html



http://ghr.nlm.nih.gov/condition/adenosine-deaminase-deficiency

http://ghr.nlm.nih.gov/condition/adenosine-deaminase-deficiency


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DNA, the molecule of heredity, Observation and experiment

people with the conditions listed. Provide guidance. o State whether the protein could be extracted for treatment before genetic

engineering techniques. o State the function of the protein and if the protein is deficient or absent. o State how successful the treatment is and whether there are alternative

treatment methods. (H) (Challenging)

Learners make outline notes following discussion on their research. Fill in any gaps with further explanation. o Explain that some people require the protein insulin to regulate their blood

glucose concentration (covered in Unit 10). (W) (Basic) o Explain that factor VIII is a protein required in the cascade of reactions

involved in blood clotting and is used to treat haemophilia (16.2.f, Unit 7). (W) (Basic)

o For SCID, explain that mutations of the ADA gene result in a lack of adenosine deaminase: a build-up of the substrate (deoxyadenosine) is toxic to immune system cells (background information: an autosomal recessive disorder). (W) (Basic)

Learners list the benefits, giving relevant examples where relevant. (F)

Note

The benefits of using bacteria or yeast cells as hosts could be a useful extension discussion.

19.3.a explain the significance of genetic engineering in improving the quality and yield of crop plants and livestock in solving the demand for food in the world, e.g. Bt maize, vitamin A enhanced rice (Golden rice

TM) and

GM salmon Key concepts Observation and experiment

Learners recall selective breeding in cattle and in crop plants (17.2.f) and discussions about the global demand for food (and energy). o Learners suggest ways in which crops and livestock may be genetically

modified to benefit populations. o Discuss why Golden rice

TM providing vitamin A is considered an

improvement in the quality of a crop plant. o Explore further ideas that crops may be modified to give a higher yield:

two main ways are making crops resistant to herbicides and resistant to pests (insects).

o Learners suggest why livestock improvements (far less common) are not as universally approved. Discuss the idea of livestock such as sheep, cattle, hens and goats growing faster, larger and being more resistant to disease.

Online http://www.cato.org/sites/cato.org/files/serials/files/regulation/2003/4/v26n1-4.pdf http://www.newscientist.com/article/dn3364-gm-crops-boost-yields-more-in-poor-countries.html#.UvhpJ_s9BOo http://www.europabio.org/do-gm-crops-really-have-higher-yields http://www.gmo-compass.org/eng/agri_biotechnology/breeding_aims/147.pest_resistant_cr

http://www.cato.org/sites/cato.org/files/serials/files/regulation/2003/4/v26n1-4.pdf



http://www.newscientist.com/article/dn3364-gm-crops-boost-yields-more-in-poor-countries.html#.UvhpJ_s9BOo




http://www.europabio.org/do-gm-crops-really-have-higher-yields

http://www.europabio.org/do-gm-crops-really-have-higher-yields

http://www.gmo-compass.org/eng/agri_biotechnology/breeding_aims/147.pest_resistant_crops.html




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o Debate the farming of GM salmon (not strictly ‘livestock’), which can grow to a marketable size much quicker than non-GM salmon. (W) (Basic) (Challenging)

Learners write an account explaining why crops genetically modified for herbicide and pest resistance would lead to increased yields. (I) (Basic)

Learners state ways in which livestock can be modified, giving examples to help their answer. (I) (Basic)

Learners outline the advantages and disadvantages of crop improvement by conventional breeding techniques compared to genetic modification. (F)

Extension: learners research examples of crop improvement by genetic modification (such as frost resistance, ability to fix nitrogen, increased time for fruit spoilage, drought resistance, etc.) and of livestock improvement. (H) (Challenging)

ops.html http://www.efsa.europa.eu/en/topics/topic/gmanimals.htm Textbooks/Publications Bio Factsheet 13: Genetic engineering Bio Factsheet 69: Genetic engineering in agriculture Bio Factsheet 192: Investigating weeds and crop yield. Past Papers Paper 43, June 2011, Q5 (a) Paper 42, June 2012, Q4 (a)

19.3.b outline the way in which the production of crops such as maize, cotton, tobacco and oil seed rape, may be increased by using varieties that are genetically modified for herbicide resistance and insect resistance Key concepts Observation and experiment

In groups, learners use resources to prepare annotated flow diagrams summarising one example of crop improvement from the list in the learning objective. o Copies of the summary diagrams are made and shared with the rest of the

class.

Learners research and produce summary notes about the use of Agrobacterium tumefaciens as one of the most common vectors and other methods such as electroporation and ‘gene guns’ to deliver genetic material into host plant cells.

Learners find, analyse and evaluate data that compares the yields of GM crops with non-GM crops. (H) (Challenging)

Online http://www.gmo-compass.org/eng/grocery_shopping/crops/24.genetically_modified_rice.html http://www.nature.com/scitable/knowledge/library/use-and-impact-of-bt-maize-46975413 http://en.wikipedia.org/wiki/Golden_rice http://www.goldenrice.org/ Textbooks/Publications Bio Factsheet 13: Genetic engineering Bio Factsheet 69: Genetic engineering in agriculture Bio Factsheet 192: Investigating weeds and crop yield.


http://www.efsa.europa.eu/en/topics/topic/gmanimals.htm

http://www.efsa.europa.eu/en/topics/topic/gmanimals.htm

http://www.gmo-compass.org/eng/grocery_shopping/crops/24.genetically_modified_rice.html




http://www.nature.com/scitable/knowledge/library/use-and-impact-of-bt-maize-46975413



http://www.goldenrice.org/


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19.3.c discuss the ethical and social implications of using genetically modified organisms (GMOs) in food production Key concepts Observation and experiment

Learners use guidelines to research some ethical and social implications of using GMOs, and then debate and discuss these points in class. (W) (H) (Basic)

Learners produce summary points about the topic. (I) (Challenging)

Note

Advise learners to look at the source of funding and editorial policy of websites to gauge whether the information is objective and impartial.

Online http://technyou.education.csiro.au/module/ethics-food-and-agriculture/page/204/issues http://www.i-sis.org.uk/GE-ethics.php http://www.beep.ac.uk http://www.salmonnation.com/fish/gefish.html http://www.oceanconservancy.org/our-work/aquaculture/aquaculture-genetically.html Textbooks/Publications Bio Factsheet 13: Genetic engineering. Bio Factsheet 106: Ethical issues in A-level Biology Bio Factsheet 137: GM Farm Scale Evaluation Trials. Past Papers Paper 43, June 2011, Q5 (b)(c)(d) Paper 42, June 2012, Q4 (e)

19.1.c describe the principles of the polymerase chain reaction (PCR) to clone and amplify DNA (the role of Taq polymerase should be emphasised) Key concepts Biochemical processes, DNA, the molecule of heredity, Observation and experiment

Use a question and answer session to agree that: the desired gene used in the genetic engineering process needs to be cloned (19.1.b); DNA polymerase is required to replicate DNA (Unit 3); the DNA strands are held together strongly by many (individually) weak hydrogen bonds. (W) (Basic)

Explain that, outside the cell, heat (approximately 90°C) can be used to separate the DNA strands. o Learners explain why heat stable polymerase enzymes are required. o Introduce Taq polymerase derived from the thermophilic bacterium

Thermus aquaticus, and discuss how this enzyme’s thermostable structure also allows it to have a long shelf life.

o Explain what primers are before explaining their role in dictating the

Online http://www.genome.gov/Glossary/index.cfm?id=159 http://www.web-books.com/MoBio/Free/Ch9E.htm http://www.saps.org.uk/secondary/teaching-resources/119-investigating-plant-evolution-amplifying-dna-using-pcr Textbooks/Publications

http://technyou.education.csiro.au/module/ethics-food-and-agriculture/page/204/issues



http://www.i-sis.org.uk/GE-ethics.php

http://www.beep.ac.uk/

http://www.salmonnation.com/fish/gefish.html

http://www.salmonnation.com/fish/gefish.html

http://www.oceanconservancy.org/our-work/aquaculture/aquaculture-genetically.html



http://www.genome.gov/Glossary/index.cfm?id=159

http://www.genome.gov/Glossary/index.cfm?id=159

http://www.web-books.com/MoBio/Free/Ch9E.htm

http://www.web-books.com/MoBio/Free/Ch9E.htm

http://www.saps.org.uk/secondary/teaching-resources/119-investigating-plant-evolution-amplifying-dna-using-pcr





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correct section of DNA to be copied and enabling Taq polymerase attachment. (W) (Challenging)

Using diagrams, provide an overview of PCR. Involve learners in explanations of the benefits of Taq polymerase stability (heating and many cycles). (W) (Basic) o Learners label the diagrams and produce a two-column table: main stage

and corresponding explanations. (I) (Challenging)

Learners match statements of the main stages with explanations of why they are carried out, they then sequence them. (F)

Learners match statements of the components involved to their role in the process. (F)

Note

Explanation of a primer can be limited to the idea of a short nucleotide sequence that binds to the DNA template strand at a specific sequence, so enabling chain elongation.

T. aquaticus was discovered in 1969 in Yellowstone National Park in Wyoming, USA, noted for its hot springs and geysers.

Bio Factsheet 67: Modern techniques in biology: genetics.

19.1.d describe and explain how gel electrophoresis is used to analyse proteins and nucleic acids, and to distinguish between the alleles of a gene (limited to the separation of polypeptides and the separation of DNA fragments cut with restriction endonucleases) Key concepts Biochemical processes, DNA, the molecule of heredity, Observation and experiment

Show learners an electrophoresis kit (or a photograph of a kit), explaining the principles and outlining the technique. o Include discussion on: the composition of the gel (size of ‘pores’ formed

by the fibrous matrix); ability to alter the voltage applied and/or the ‘run’ time; methods used e.g. stains or fluorescent dyes to ‘see’ separated bands (if not visible).

o Prompt learners to suggest and explain the factors affecting movement through the gel. Ensure they appreciate that separation of a mixture will be based on: size/length/mass; and charge (discuss resistance to flow). (W) (Basic)

Learners explain why samples of DNA/RNA will move towards the anode (phosphate groups give a negative charge), and how restriction enzymes (see 19.1.h) will give specific different-sized fragments. o Explain that the solution containing the DNA fragments can be treated so

the charge is the same for all; hence they are separated by size/length (all fragments same shape).

Practical booklet 12 Online http://www.genome.gov/Glossary/?id=56 http://www.life.uiuc.edu/molbio/geldigest/electro.html#run http://www.ncbe.reading.ac.uk/NCBE/MATERIALS/menu.html http://www.bio-rad.com/ http://www.edvotek.com/ http://www.medicine.mcgill.ca/physio/vlab/Other_exps/endo/electrophoresis.htm http://www.bio-rad.com/en-ca/applications-technologies/protein-electrophoresis

http://www.genome.gov/Glossary/?id=56

http://www.genome.gov/Glossary/?id=56

http://www.life.uiuc.edu/molbio/geldigest/electro.html#run

http://www.life.uiuc.edu/molbio/geldigest/electro.html#run

http://www.ncbe.reading.ac.uk/NCBE/MATERIALS/menu.html

http://www.ncbe.reading.ac.uk/NCBE/MATERIALS/menu.html

http://www.bio-rad.com/

http://www.edvotek.com/

http://www.medicine.mcgill.ca/physio/vlab/Other_exps/endo/electrophoresis.htm



http://www.bio-rad.com/en-ca/applications-technologies/protein-electrophoresis




V3.1 133


o Discuss how RNA molecules will be of different lengths and hence separation by size will work. (W) (Basic)

Learners use kits (or simulations) to carry out gel electrophoresis of DNA. (I) (Challenging)

Using resources, learners draw an annotated diagram that helps to outline the principles behind the process, using nucleic acids as an example. (I) (Basic)

Learners recall protein molecular structure to realise that a mixture can be different lengths, charges and shapes, hence requiring a different electrophoresis set-up to DNA. (W) (Basic) o Explain that a buffer can be used to provide a uniform negative charge

and unfold the proteins.

Learners research identification of a protein by protein blotting or antibody tagging. (H) (Challenging)

Learners investigate the uses of gel electrophoresis in the analysis of proteins and nucleic acids and a ‘class list’ made of each to display. (W) (H) (Basic)

Extension: learners research the advantages and disadvantages of the two main gels, agarose and polyacrylamide. (I) (Challenging)

Learners discuss the differences that may exist between alleles of a gene. o Discuss how alleles of only slightly different length can be detected with

the correct gel composition. o Explain that if alleles are the same or similar, undetectable length,

restriction enzymes could be used to obtain fragments: different fragments with different sequences can be detected. An alternative is using a DNA probe.

o Mention that there are DNA sequence ‘libraries’ to obtain known sequences to act as markers.

o Use sickle cell anaemia to exemplify how differences between alleles can sometimes be detected by sampling the protein products, e.g. the two types of haemoglobin (confirms carrier status). (W) (Challenging

Practical booklet 12 is a protocol for separating dyes by gel electrophoresis that demonstrates the principles involved in separating DNA.

Note

Generally, small agarose gels are used to separate DNA (lower voltage for approximately 1-2 hours) whereas large polyacrylamide gels are required for

http://learn.genetics.utah.edu/content/labs/gel/ http://www.biotechlearn.org.nz/themes/dna_lab/gel_electrophoresis www.ncbe.reading.ac.uk/ncbe/protocols/PDF/DiceSG.pdf http://www.stanford.edu/group/hopes/cgi-bin/wordpress/2011/03/genetic-testing/ Textbooks/Publications Bio Factsheet 67: Modern techniques in Biology: Genetics. Past Papers Paper 41, June 2012, Q3 (b) Paper 42, June 2013, Q2 (b)

http://learn.genetics.utah.edu/content/labs/gel/

http://learn.genetics.utah.edu/content/labs/gel/

http://www.biotechlearn.org.nz/themes/dna_lab/gel_electrophoresis

http://www.biotechlearn.org.nz/themes/dna_lab/gel_electrophoresis

http://www.ncbe.reading.ac.uk/ncbe/protocols/PDF/DiceSG.pdf

http://www.ncbe.reading.ac.uk/ncbe/protocols/PDF/DiceSG.pdf

http://www.stanford.edu/group/hopes/cgi-bin/wordpress/2011/03/genetic-testing/




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proteins (higher voltages for about 4 hours). Different electrophoresis tanks and power packs are required.

Links to 19.2.d: genetic screening can involve gel electrophoresis, e.g. identifying carriers. In some cases restriction enzymes are used, or probes to locate specific base sequences. o Cystic fibrosis: some mutant alleles have large deletions. o Huntington’s disease: the mutant allele of the Huntington gene has tri-

nucleotide repeat sequences. o Some cases of haemophilia: a mutant allele in the factor VIII gene has an

insertion that inactivates the gene.

19.2.g outline the use of PCR and DNA testing in forensic medicine and criminal investigations Key concepts DNA, the molecule of heredity, Observation and experiment

Explain that pure DNA or DNA mixed with other biological materials (e.g. in a tissue sample such as dried blood) is analysed and compared to existing profiles or known markers. o Explain what variable number tandem repeats (VNTRs) are and detail

their importance in an analysis, including: a particular VNTR occurs at a specific locus; for a particular VNTR different individuals can have a different number of repeats (so different lengths of the DNA section); VNTRs that are very variable in different individuals can be used as markers. (W) (Challenging)

Learners suggest the role of PCR (amplify the quantity of each VNTR marker in the sample). (W) (Basic)

Ensure learners understand that the chance that two individuals (except for identical twins) have exactly matching DNA profiles (genetic fingerprints) for these selected markers is virtually nil. (W) (Challenging)

Learners use resources to extract the main points of the technique of genetic fingerprinting and list as bullet points. (I) (Challenging)

Learners carry out analyses of different results of genetic fingerprints or make up their own worksheet containing simulated results from a crime scene to swap within the class for another learner to analyse. (P) (I) (Basic)

Learners explain the role of PCR in DNA fingerprinting and outline the principles as applied to VNTRs: o Very small samples of DNA can be analysed. o Millions of DNA copies can be produced (so can run many tests on the

same original DNA sample).

Online https://koshland-science-museum.org/sites/all/exhibits/exhibitdna/index.jsp http://learn.genetics.utah.edu/content/labs/pcr/ http://www.pbs.org/wgbh/nova/sheppard/analyze.html Past Papers Paper 41, June 2012, Q3 (a)

https://koshland-science-museum.org/sites/all/exhibits/exhibitdna/index.jsp



http://learn.genetics.utah.edu/content/labs/pcr/

http://learn.genetics.utah.edu/content/labs/pcr/

http://www.pbs.org/wgbh/nova/sheppard/analyze.html

http://www.pbs.org/wgbh/nova/sheppard/analyze.html


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o Longer VNTRs will be impeded more by the gel (move a shorter distance in the same time than the shorter VNTRs). (I) (Challenging)

19.2.a define the term bioinformatics Key concepts Observation and experiment

Learners work out what the term bioinformatics means: biology and data, computer science and information technology merged into one (remind them about statistics). (W) (G) (Basic)

Explain that there are linked databases holding freely available, continually updated, information on: nucleotide sequences of genes (gene sequences); whole genome sequences; mutation sequences; amino acid sequences of proteins; protein structures; phenotypic data. o Ideas for learners to consider: input, storage and retrieval of biological

information for analysis; data that can be searched is increasing exponentially.

o Learners define the term bioinformatics and list the principles involved. (W) (I) (Challenging)

Demonstrate how to use BLAST (basic local alignment search tool), which compares nucleotide or protein sequences to databases. When a match is found, the statistical significance of the match is calculated. o Show learners how a nucleotide sequence can be matched to an amino

acid sequence and how these may match up to known genes belonging to organisms. (W) (Challenging)

Learners explore the world of bioinformatics for themselves if there is internet access and report back findings. (W) (H) (Challenging)

Note

Suitable databases to explore are Ensembl (genome), GenBank (DNA sequence), UniProt (protein sequence), PDB (protein structure) and COSMIC (somatic mutations in cancer).

Online http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1002789 http://www.biotnet.org/training-materials/das-game http://www.genecards.org/# http://www.genome.gov/glossary/index.cfm?id=17 http://www.malacards.org/ http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Genes-Genomes-and-Health/WTDV027167.htm http://www.ebi.ac.uk/about http://www.bioinformaticsatschool.eu/ http://www.nature.com/scitable/topicpage/genomics-enables-scientists-to-study-genetic-variability-6526364

19.2.b outline the role of bioinformatics following the sequencing of genomes, such as those of humans and parasites, e.g. Plasmodium (details of methods of DNA sequencing are not required)

Give an outline of the human genome project (HGP). o With prompting, learners suggest the role of bioinformatics, such as in:

targeting drug design to the individual; investigating evolutionary links by comparing gene and protein sequence data; searching for the functions of genes; identifying mutations; identifying genetic risk factors; gene therapy. (W) (Challenging)

Online http://www.bioinformatics.org/wiki/Bioinformatics_FAQ http://www.genecards.org/# http://www.genome.gov/glossary/index.cfm?id=17 http://www.malacards.org/

http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1002789



http://www.biotnet.org/training-materials/das-game

http://www.biotnet.org/training-materials/das-game

http://www.genecards.org/



http://www.malacards.org/

http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Genes-Genomes-and-Health/WTDV027167.htm





http://www.ebi.ac.uk/about

http://www.bioinformaticsatschool.eu/




http://www.bioinformatics.org/wiki/Bioinformatics_FAQ

http://www.bioinformatics.org/wiki/Bioinformatics_FAQ

http://www.genecards.org/



http://www.malacards.org/


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Revise Plasmodium and the control of malaria, including problems with finding a vaccine (Unit 5). (W) (Basic) o Then open up a discussion about the role of bioinformatics following the

sequencing of genomes of the species of Plasmodium. o Learners suggest the benefits in identifying the genes involved in

antigenic variation and in evading the immune response (information gained about how some species are more invasive than others).

o Learners discuss how information could be used in the search for new drugs and vaccines. (W) (G) (Challenging)

Learners write an account of the role of bioinformatics following the sequencing of genomes, referring to the HGP and the Plasmodium genome and making relevant links to other relevant learning objectives. (F)

http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Genes-Genomes-and-Health/WTDV027167.htm http://www.ebi.ac.uk/about http://www.bioinformaticsatschool.eu/ http://www.nature.com/scitable/topicpage/genomics-enables-scientists-to-study-genetic-variability-6526364 http://www.sanger.ac.uk/resources/downloads/protozoa/plasmodium-falciparum.html http://www.nature.com/nature/journal/v419/n6906/full/nature01097.html http://web.ornl.gov/sci/techresources/Human_Genome/project/timeline.shtml http://web.ornl.gov/sci/techresources/Human_Genome/project/info.shtml http://web.ornl.gov/sci/techresources/Human_Genome/publicat/genegateway/GeneGatewayHandout.pdf http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taxonomy.html http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Genes-Genomes-and-Health/WTDV027173.htm http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Genes-Genomes-and-Health/Videos-genomes-and-genetic-






http://www.ebi.ac.uk/about

http://www.bioinformaticsatschool.eu/




http://www.sanger.ac.uk/resources/downloads/protozoa/plasmodium-falciparum.html



http://www.nature.com/nature/journal/v419/n6906/full/nature01097.html

http://www.nature.com/nature/journal/v419/n6906/full/nature01097.html

http://web.ornl.gov/sci/techresources/Human_Genome/project/timeline.shtml



http://web.ornl.gov/sci/techresources/Human_Genome/project/info.shtml

http://web.ornl.gov/sci/techresources/Human_Genome/project/info.shtml

http://web.ornl.gov/sci/techresources/Human_Genome/publicat/genegateway/GeneGatewayHandout.pdf



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taxonomy.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taxonomy.html






http://www.wellcome.ac.uk/Education-resources/Education-and-learning/Big-Picture/All-issues/Genes-Genomes-and-Health/Videos-genomes-and-genetic-testing/WTDV027199.htm






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testing/WTDV027199.htm

19.2.d outline the advantages of screening for genetic conditions (reference may be made to tests for specific genes such as those for breast cancer, BRCA1 and BRCA2, and genes for haemophilia, sickle cell anaemia, Huntington’s disease and cystic fibrosis) Key concepts DNA, the molecule of heredity, Natural selection, Observation and experiment

Learners suggest what is involved in genetic screening (using family history and, if the test is available, analysing tissue samples for DNA) and name conditions for which genetic screening is available. o Ensure the conditions listed are included and explained. (W)

Explain what is meant by genetic counselling. (W) (Basic)

Brainstorm advantages of screening for genetic conditions and complete the list if necessary. o Provides information about increased risk of having genetic conditions. o Identifies carriers. o Early diagnosis, including identification of disorders in embryos. o Identifies conditions in foetuses (early treatment may be possible and

allows parents to prepare. o Enables decisions to be made about having children or having follow-up

treatment. (W) (Challenging)

Learners research and make outline notes on the genetic conditions named, then match up advantages from the brainstorm list to each condition. (I) (Basic)

Extension: learners suggest some of the disadvantages of screening. (I) (Challenging)

Note

This topic needs careful handling.

Background: some genetic conditions are more common in certain groups as a result of common ancestry (sharing similar genetic make-up), e.g. cystic fibrosis is most common in Caucasians; sickle cell anaemia is common in West and East African, African-American and Mediterranean populations; Huntington’s disease is more common in Europe and countries with European links.

Online http://www.nlm.nih.gov/medlineplus/cysticfibrosis.html http://ghr.nlm.nih.gov/gene/CFTR http://www.ygyh.org/cf/whatisit.htm http://resources.schoolscience.co.uk/BBSRC/casestudies/cystic.pdf http://learn.genetics.utah.edu/content/disorders/screening/ http://www.hdfoundation.org/html/hdsatest.php http://www.merck.com/mmhe/sec22/ch256/ch256b.html Textbooks/Publications Bio Factsheet 110: Genetic Disease in Humans. Bio Factsheet 134: Cystic Fibrosis Bio Factsheet 215: Genetic Testing and Screening

19.2.e outline how genetic diseases can be treated with gene therapy and

Explain that in gene therapy, the aim is for affected cells to take up the normal, non-mutated gene and produce the normal, functioning protein product.

Online http://www.nlm.nih.gov/medlineplus/cysticfibrosis.html


http://www.nlm.nih.gov/medlineplus/cysticfibrosis.html


http://ghr.nlm.nih.gov/gene/CFTR

http://www.ygyh.org/cf/whatisit.htm

http://resources.schoolscience.co.uk/BBSRC/casestudies/cystic.pdf


http://learn.genetics.utah.edu/content/disorders/screening/


http://www.hdfoundation.org/html/hdsatest.php

http://www.hdfoundation.org/html/hdsatest.php

http://www.merck.com/mmhe/sec22/ch256/ch256b.html





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discuss the challenges in choosing appropriate vectors, such as viruses, liposomes and naked DNA (reference may be made to SCID, inherited eye diseases and cystic fibrosis) Key concepts DNA, the molecule of heredity, Observation and experiment

o Prompt learners to suggest methods of delivery of the normal gene, such as viruses and liposomes (you may need to describe liposomes). (W) (Basic)

Learners discuss in groups why viruses may be ideal vectors, and then share ideas with the class. Features: small; can be manipulated to incorporate the gene, be harmless and not trigger an immune response; target particular cells and enter, or inject the gene into the cell; have mechanisms to pass through the mucus lining cells; can integrate their nucleic acid into the target cell genome. o Explain that the ‘ideal’ virus is difficult to find as it will be almost impossible

to fit all the criteria. (W) (G) (Challenging)

Learners research the advantages of the type of virus used in the gene therapy for eye disease and explain why the eye is a good candidate for gene therapy. (I) (Challenging)

Learners research (also use knowledge of cell surface membrane structure) why liposomes can be used as vectors. o Learners explain how liposomes have been used in clinical trials for the

treatment of cystic fibrosis. o Extension: learners include an account of the problems faced in treating

this condition. (I) (Challenging)

Explain that SCID has been a successful candidate for gene therapy: the gene for adenosine deaminase is introduced into T-lymphocytes removed from children with SCID. The lymphocytes are cultured in tissue culture with a viral vector and then the cells injected back into the child. (W) (Basic)

Extension: learners research the historical work done by French-Anderson, Blaese and Rosenburg on SCID gene therapy and explain how the therapy was carried out. (H) (Basic)

Discuss any recent successes in naked DNA therapy. Explain that initial results showed that direct injection into muscle has indicated some success in uptake; there has also been uptake by liver cells. (W) (Basic)

http://ghr.nlm.nih.gov/gene/CFTR http://www.ygyh.org/cf/whatisit.htm http://resources.schoolscience.co.uk/BBSRC/casestudies/cystic.pdf http://learn.genetics.utah.edu/content/disorders/screening/ http://www.merck.com/mmhe/sec22/ch256/ch256b.html http://www.vision-research.eu/index.php?id=696 http://www.newscientist.com/article/dn24879-gene-therapy-restores-sight-in-people-with-eye-disease.html http://www.newscientist.com/article/mg22029413.200-bubble-kid-success-puts-gene-therapy-back-on-track.html http://history.nih.gov/exhibits/genetics/sect4.htm http://www.genemedresearch.ox.ac.uk/genetherapy/cfgt.html http://www.extremetech.com/extreme/171873-naked-dna-gene-therapy-used-to-non-invasively-cure-heart-disease http://ghr.nlm.nih.gov/handbook/therapy/procedures Textbooks/Publications Bio Factsheet 51: Gene therapy Past Papers Paper 41, Nov 2011, Q5 Paper 43, Nov 2013, Q10 (a)

http://ghr.nlm.nih.gov/gene/CFTR

http://www.ygyh.org/cf/whatisit.htm







http://www.vision-research.eu/index.php?id=696

http://www.vision-research.eu/index.php?id=696

http://www.newscientist.com/article/dn24879-gene-therapy-restores-sight-in-people-with-eye-disease.html



http://www.newscientist.com/article/mg22029413.200-bubble-kid-success-puts-gene-therapy-back-on-track.html




http://history.nih.gov/exhibits/genetics/sect4.htm

http://history.nih.gov/exhibits/genetics/sect4.htm

http://www.genemedresearch.ox.ac.uk/genetherapy/cfgt.html

http://www.genemedresearch.ox.ac.uk/genetherapy/cfgt.html

http://www.extremetech.com/extreme/171873-naked-dna-gene-therapy-used-to-non-invasively-cure-heart-disease




http://ghr.nlm.nih.gov/handbook/therapy/procedures

http://ghr.nlm.nih.gov/handbook/therapy/procedures


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19.2.f discuss the social and ethical considerations of using gene testing and gene therapy in medicine (reference should be made to genetic conditions for which treatments exist and where none exist, also to IVF, embryo biopsy and preselection and to therapeutic abortions) Key concepts Observation and experiment

Explain that there are social and ethical considerations (see Note) of using gene testing and gene therapy. o Agree that not all genetic conditions are treatable. o Discuss issues arising from: gene testing embryos by performing an

embryo biopsy; couples deciding on IVF treatment for embryo testing and preselection for implantation.

o If not discussed in 19.2.d, explain briefly what is meant by therapeutic abortion. (W) (Basic)

Learners write their ideas under four headings on pieces of paper ‘Gene testing – social consideration’; ‘Gene testing – ethical consideration’; ‘Gene therapy - social consideration’; Gene therapy - ethical consideration’. o Learners justify their statements to a small group and, if agreed, add it to a

poster. o Display the posters for learners to consider and make notes. (G) (I)


Note

This needs to be treated with sensitivity.

Social = related to human society, e.g. interdependence, mutual relationships, cooperation for all to benefit.

Ethics = set of agreed standards, determine what is acceptable, followed by a group of individuals, regulated behaviour.

Online http://www.medscape.com/viewarticle/505222_4 http://ghr.nlm.nih.gov/handbook/therthe/ethics Textbooks/Publications Bio Factsheet 51: Gene therapy Past Papers Paper 41, Nov 2011, Q5

http://www.medscape.com/viewarticle/505222_4

http://www.medscape.com/viewarticle/505222_4

http://ghr.nlm.nih.gov/handbook/therthe/ethics

http://ghr.nlm.nih.gov/handbook/therthe/ethics


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Unit 9: Respiration


Learners should be familiar with the concept of energy transfer and understand that energy contained within biological compounds can be released for use by the cell. They should have a sound understanding of what a molecule is, and understand chemical formulae and equations. It would be helpful if they understood the concept of oxidation and reduction, at least at a simple level. Context

This unit considers the key concept of biochemical processes and focuses on how the energy contained within food molecules such as glucose is transferred into the universal energy currency of ATP for use in the cell. All unicellular and multicellular organisms use the organic compound ATP to drive the energy-requiring processes that occur in cells. There are many direct links to other areas of the syllabus, such as: the structure and role of glucose and lipids from Unit 1; mitochondrion structure and function from Unit 2; the role of enzymes in metabolic reactions from Unit 2; and ATP from Units 1 and 3. The unit has close links with photosynthesis in Unit 11, which also covers the concept of energy transfer and ATP synthesis. Throughout the syllabus there are examples of the use of ATP for biochemical processes. Outline

This unit covers the need for energy in living organisms and the universal occurrence of ATP as energy currency. The four main stages of aerobic respiration, glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation are described. A distinction is made between the synthesis of ATP by substrate-linked reactions and by oxidative phosphorylation; the role of coenzymes in these stages is made clear. A comparison is made between aerobic and anaerobic respiration in mammals and in yeast. An explanation of RQ is given and different respiratory substrates are considered. Learners use respirometers to make quantitative studies of respiration and have an opportunity to improve planning and evaluative skills. This unit lends itself to sequential descriptions and the construction of flow diagrams to illustrate the many different stages that occur within the overall process. Teaching time



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12.1.a outline the need for energy in living organisms, as illustrated by anabolic reactions, such as DNA replication and protein synthesis, active transport, movement and the maintenance of body temperature Key concepts Cells as the units of life, Biochemical processes

Brainstorm ideas to construct a disorganised set of statements. Encourage learners to include examples from prokaryotes and eukaryotes. (W) (Basic) o Learners give headings for main uses of energy in organisms,

accompanied by bullet-point notes. o Agree that some examples from the brainstorming session could be

grouped, e.g. under ‘movement’. Bullet points could include: bacteria and flagellar movement (outline the difference between prokaryotic and eukaryotic flagella); protoctists and amoeboid movement, synchronous rhythm of cilia and flagellar movement; discharge of spores in fungi; muscle contraction in animals; translocation of sugars or closure of flytrap (see 15.2.a) in plants.

o Learners recall Unit 1, Biological molecules, for relevant bullet points for anabolic reactions. (I) (Basic)

Note

Ensure that learners understand the meanings of the terms metabolism and catabolism.

Online http://www.rsc.org/Education/Teachers/Resources/cfb/index.htm

12.1.b describe the features of ATP that make it suitable as the universal energy currency Key concepts Biochemical processes

Use questioning to remind learners of the structure of an ATP molecule. Ensure learners realise that energy is released at each step of the complete hydrolysis of ATP:

ATP ADP AMP (W) (Basic)

Write out a list of features that make ATP suitable as the universal energy currency. o Learners add brief notes to explain each feature, including a diagram

showing the one-step process of release of energy from ATP hydrolysis and synthesis of ATP from ADP and Pi (inorganic phosphate). (I) (Basic)

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATP.html Textbooks/Publications Bio Factsheet 129: ATP – what it is, what it does Past Papers Paper 41, June 2011, Q7 (a)

12.2.a list the four stages in aerobic respiration (glycolysis, link reaction, Krebs cycle and oxidative phosphorylation) and state where each occurs in eukaryotic cells

Learners recall an overall equation for aerobic respiration: glucose + oxygen energy + water + carbon dioxide o State that ATP should be substituted for ‘energy’. o Learners write out a balanced equation using the correct chemical

formulae (for completeness, mention heat energy). (W) (Basic)

Learners write out the overall equation for aerobic respiration and produce a

Online http://leavingbio.net/RESPIRATION-%28ordinary%20level%29.htm http://leavingbio.net/respiration-%28higher%20level%29.htm



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATP.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATP.html

http://leavingbio.net/RESPIRATION-%28ordinary%20level%29.htm

http://leavingbio.net/RESPIRATION-%28ordinary%20level%29.htm

http://leavingbio.net/respiration-%28higher%20level%29.htm

http://leavingbio.net/respiration-%28higher%20level%29.htm


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Key concepts Cells as the units of life, Biochemical processes, Natural selection

large diagram (full page) of a cell (cytoplasm labelled), containing a (not-to-scale) large labelled mitochondrion with visible cristae (1.2.b, Unit 2). o Learners write the heading of each of the four stages in the correct

locations and add to this later. (I) (Basic)

Note

Glycolysis: can be shown later as glucose pyruvate.

Link reaction: pyruvate entering the mitochondrial matrix and the reaction with coenzyme A, acetyl coenzyme A, enters the cycle.

Krebs cycle: main stages of the cycle only, showing involvement of FAD and NAD, decarboxylation and ATP production.

Oxidative phosphorylation: NADH and FADH leaving the cycle to the crista, ATP formation.

Highlight to learners the similar biochemistry in different species of organisms (link to the evidence for evolution in Unit 7).

Past Papers Paper 41, June 2011, Q7 (b)(iii)

12.2.b outline glycolysis as phosphorylation of glucose and the subsequent splitting of fructose 1,6-bisphosphate (6C) into two triose phosphate molecules, which are then further oxidised to pyruvate with a small yield of ATP and reduced NAD Key concepts Biochemical processes

Build up the idea that: (i) respiration is a series of enzyme-controlled metabolic reactions, (ii) it takes place in all living cells, and (iii) energy contained in molecules such as glucose is used to make ATP molecules. (W) (Basic)

Explain that glycolysis occurs in the cytoplasm (in virtually every organism) in both anaerobic and aerobic respiration. (W) (Basic)

Learners copy out a skeleton flow diagram of glycolysis, with glucose, the two intermediates, and pyruvate shown (missing intermediate stages could be signified by the correct number of arrows in between). o With question and answer prompts, learners build up their flow charts with

detail and explanatory annotations. Ensure they understand that: coenzyme NAD is required to act as an electron (hydrogen) carrier for the enzyme-catalysed reaction (see 12.1.d); NADH has different fates, depending on whether or not oxygen is available.

o Learners show clearly the tally of ATP use and production. o The number of carbons for each of the molecules in the process is shown

in brackets. (W) (I) (Challenging)

Explain that in glycolysis ATP can be formed when another phosphorylated organic compound transfers a phosphate to ADP: so ATP is synthesised as a

Online http://glycolysis.co.uk/ www.science.smith.edu/departments/Biology/Bio231/glycolysis.html http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html http://www.johnkyrk.com/glycolysis.html http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter7/how_glycolysis_works.html http://resources.teachnet.ie/foneill/respir.html Past Papers Paper 41, Nov 2011, Q6 (a)(b)

http://glycolysis.co.uk/

http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html



http://www.johnkyrk.com/glycolysis.html

http://www.johnkyrk.com/glycolysis.html

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter7/how_glycolysis_works.html




http://resources.teachnet.ie/foneill/respir.html

http://resources.teachnet.ie/foneill/respir.html


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product in a substrate-linked reaction (see 12.1.c). (W) (Basic)

Note

If able learners are given a more complete picture, stress that the additional intermediate steps and compounds are not required learning.

Mention that ‘substrate-level phosphorylation’ is an alternative term to substrate-linked ATP synthesis.

12.2.c explain that, when oxygen is available, pyruvate is converted into acetyl (2C) coenzyme A in the link reaction Key concepts Biochemical processes, Organisms in their environment

Explain that pyruvate travels from the cytosol through the inner and outer mitochondrial membranes to enter the matrix where the link reaction occurs. (W) (Basic)

Learners study and comment on the link reaction equation before making notes. They should note that: o Coenzyme A transfers an acetyl group to the Krebs cycle (see 12.1.d). o Carbon dioxide is given off, hence decarboxylation* occurs. o NAD acts as an electron (hydrogen) carrier, hence dehydrogenation*

occurs. o The reaction occurs twice for each original glucose molecule. (G) (I)


Note

See 12.2.e also.

Online http://www.wiley.com/legacy/college/boyer/0470003790/animations/tca/tca.htm http://www.science.smith.edu/departments/Biology/Bio231/krebs.html http://www.johnkyrk.com/krebs.html http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

12.2.d outline the Krebs cycle, explaining that oxaloacetate (a 4C compound) acts as an acceptor of the 2C fragment from acetyl coenzyme A to form citrate (a 6C compound), which is reconverted to oxaloacetate in a series of small steps Key concepts Biochemical processes

Build up the simple diagram showing the required steps in the Krebs cycle, including the number of carbon atoms for the three named compounds. o Emphasise: its cyclic nature; enzyme-controlled reactions (no names

required); more steps are involved than is shown. (W) (I) (Basic)

Explain that two carbon dioxide molecules are released for one turn of the cycle and ask learners to decide where this is and add to the diagram. o Tell learners where substrate-linked phosphorylation occurs (see 12.2.b

and 12.1.c) so they can add ATP formation to their diagram (knowledge of GTP not required).

o Learners volunteer the role of NAD and FAD, and then add the formation of NADH and FADH to their cycle (see 12.2.d). (I) (Basic)

Learners state and explain how many turns of the cycle occur for each molecule of glucose. (I) (Basic)

Online http://www.wiley.com/legacy/college/boyer/0470003790/animations/tca/tca.htm http://www.science.smith.edu/departments/Biology/Bio231/krebs.html http://www.johnkyrk.com/krebs.html Past Papers Paper 43, June 2011, Q6 (a)(b)

http://www.wiley.com/legacy/college/boyer/0470003790/animations/tca/tca.htm



http://www.science.smith.edu/departments/Biology/Bio231/krebs.html


http://www.johnkyrk.com/krebs.html

http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html









http://www.johnkyrk.com/krebs.html


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Allow learners a short time to look at their diagrams, and then talk through the steps while they draw the cycle. (F)

Note

Learners should avoid websites that have far more detail than required.

12.2.e explain that reactions in the Krebs cycle involve decarboxylation and dehydrogenation and the reduction of NAD and FAD Key concepts Biochemical processes

Learners add annotations to the Krebs cycle: o dehydrogenation occurs: the NADH and FADH contain hydrogen atoms

protons and electrons (from the respiratory substrate) o decarboxylation of intermediates occurs: carbon dioxide is given off. (I)

(Basic)

Give learners time to assimilate the information on their diagrams before testing them. (I) (Challenging)

Note

Dehydrogenase and decarboxylase enzymes could be mentioned here (not required learning).

12.1.c explain that ATP is synthesised in substrate-linked reactions in glycolysis and in the Krebs cycle Key concepts Biochemical processes

Learners add an explanation of ATP synthesis by substrate-linked reactions to their summary diagram of 12.2.a. (W) (Basic)

Online http://sandwalk.blogspot.co.uk/2007/12/how-cells-make-atp-substrate-level.html

12.2.g explain that during oxidative phosphorylation:

energetic electrons release energy as they pass through the electron transport system

the released energy is used to transfer protons across the inner mitochondrial membrane

protons return to the mitochondrial

Learners label a basic diagram of the membrane carriers of the electron transport chain (ETC) and the ATP synthase (synthetase) complex in the inner mitochondrial / crista membrane (include labels for the mitochondrial matrix and the inter-membrane space).

With prompting and guidance, learners show on their diagram the transfer of hydrogen to the membrane from NADH and FADH and the release of the coenzymes for re-use in the Krebs cycle. (W) (Basic)

Learners contribute to build up the rest of the diagram. For the electron transport chain include: o Hydrogen from NAD/FAD split into protons and electrons.

Online http://www.science.smith.edu/departments/Biology/Bio231/etc.html Textbooks/Publications Bio Factsheet 12: Respiration Past Papers Paper 42, June 2013, Q4 (a)(i)

http://sandwalk.blogspot.co.uk/2007/12/how-cells-make-atp-substrate-level.html



http://www.science.smith.edu/departments/Biology/Bio231/etc.html

http://www.science.smith.edu/departments/Biology/Bio231/etc.html


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matrix by facilitated diffusion through ATP synthase providing energy for ATP synthesis (details of ATP synthase are not required)

Key concepts Biochemical processes

o Oxidation-reduction reactions are involved (hence ‘oxidative’) as electrons are transported down the ETC (i.e. to lower energy levels).

o Energy provided by the electron transfer is used to pump protons from the matrix into the intermembrane space.

o Oxygen (final electron acceptor) + electrons + protons produce water as a waste product.

For chemiosmosis, use learner knowledge of AS Level to discuss: o The relatively impermeability of the membrane to protons (so allowing a

build-up). o Facilitated diffusion of protons through the enzyme complex down their

concentration (and electrical) gradient. o The enzyme-catalysed synthesis of ATP from ADP and inorganic

phosphate by the movement of protons (proton-motive force). (W) (I) (Challenging)

Learners sort a set of statements into a correct sequence to outline oxidative phosphorylation and then add an outline to their summary diagram of 12.2.a. (P) (I) (Basic) (Challenging)

Learners write a sequential account of the process. (F)

12.2.f outline the process of oxidative phosphorylation including the role of oxygen as final electron acceptor (no details of the carriers are required) Key concepts Biochemical processes

Assess understanding of 12.2.g by agreeing an outline summary with learners. o Oxidative phosphorylation is the last stage in the release of energy from

the initial respiratory substrate and oxygen is the final electron acceptor. o The two linked parts to the process are the events involving the electron

transport chain and the events linked with a process known as chemiosmosis.

o The sources of the ‘energetic’ electrons are NADH and FADH from the Krebs cycle and NADH from the link reaction.

o ATP formation by oxidative phosphorylation is a process involving oxidation-reduction reactions, where the energy needed for ATP synthesis is from the transfer of electrons from a higher energy electron donor to a lower energy electron acceptor.

Learners add an outline of the link reaction, Krebs cycle and oxidative phosphorylation to their summary diagram of 12.2.a. (I) (Basic)

Note

Online http://www.stolaf.edu/people/giannini/flashanimat/metabolism/mido%20e%20transport.swf Past Papers Paper 43, June 2011, Q6 (c)

http://www.stolaf.edu/people/giannini/flashanimat/metabolism/mido%20e%20transport.swf




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Carriers do not need identifying but explain that these are membrane proteins.

Learners should be able tackle the concepts involved in 12.2.h if they have mastered the outline of 12.2.g.

Chemiosmosis as a term is not specified in a learning objective, but learners should be familiar with the term.

12.1.e (i) explain that the synthesis of ATP is associated with the electron transport chain on the membranes of mitochondria and chloroplasts (see 12.2.g) Key concepts Cells as the units of life, Biochemical processes

Only part of this learning objective is included here: explain that the synthesis of ATP is associated with the electron transport chain on the membranes of mitochondria (see 12.2.g)

With a brief written test, confirm learner knowledge and understanding of this learning objective (all details previously covered). (I) (Basic)

In preparation for Unit 11, explain that there is also an ETC located in the thylakoid membranes of chloroplasts. (W) (I) (Basic)

Online http://www.ncbi.nlm.nih.gov/books/NBK21063/

12.1.d outline the roles of the coenzymes NAD, FAD and coenzyme A in respiration Key concepts Biochemical processes

Explain that many enzymes require a non-protein (co-)factor, in their active site to help in catalysis, and that organic cofactors that associate with the enzyme during catalysis and then dissociate are known as coenzymes. (W) (Basic)

Ensure learners now understand that NAD and FAD are electron (hydrogen) carriers, so become reduced and can give electrons to electron acceptors during respiration (becoming oxidised again). o Learners should be clear that the oxidation of NADH and FADH releases

energy that can be used to synthesise ATP. (W) (Basic)

Online http://www.ebi.ac.uk/thornton-srv/databases/CoFactor/index.php

12.2.i describe the relationship between structure and function of the mitochondrion using diagrams and electron micrographs

From electron micrographs of mitochondria, learners identify the outer and inner membrane, cristae and matrix. o Learners check if 70S ribosomes and small circular DNA is visible. (P) (I)

(Basic)

Learners construct an annotated diagram summarising how the structure of a mitochondrion is adapted for its functions. (I) (Challenging)

Online http://www.johnkyrk.com/mitochondrion.html Textbooks/Publications Bio Factsheet 61: Chloroplasts and mitochondria



http://www.ebi.ac.uk/thornton-srv/databases/CoFactor/index.php

http://www.ebi.ac.uk/thornton-srv/databases/CoFactor/index.php

http://www.johnkyrk.com/mitochondrion.html

http://www.johnkyrk.com/mitochondrion.html


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12.2.k explain the production of a small yield of ATP from respiration in anaerobic conditions in yeast and in mammalian muscle tissue, including the concept of oxygen debt Key concepts Biochemical processes, Natural selection

Use flow diagrams to explain the lactate pathway in mammals and the ethanol pathway in yeast, with learners providing the main outline of glycolysis (glucose to pyruvate) and naming the location (cytoplasm). (W) (Basic)

Explain that these pathways occur when oxygen is not available, with pyruvate and ethanol acting as the final electron acceptors to produce lactate and ethanol as waste products. (W) (Basic)

Learners suggest why pyruvate needs to be processed further when no more ATP is produced (the regeneration of NAD to allow glycolysis to continue - there is a very limited quantity of NAD in each cell). (W) (Basic)

Learners add an outline to their summary diagram of 12.2.a after making their own flow diagrams. (I) (Basic)

Learners begin with oxidative phosphorylation and work backwards through earlier stages to write down a series of statements showing the consequences if oxygen is not available. (F) (Challenging)

Learners research the concept of oxygen debt and write an explanation. o Annotations can be added to the lactate pathway to show how, when

oxygen becomes available, lactate can be converted back to pyruvate, which can then be converted to glucose and glycogen for storage, or enter the Krebs cycle. (H) (Challenging)

Extension practical: learners investigate the effect of different concentrations of ethanol on rates of respiration in yeast. (I) (Challenging)

Note

Mention to learners that anaerobic respiration in yeast is also known as alcoholic or ethanol fermentation and that anaerobic respiration in mammalian tissues is also known as lactic acid or lactate fermentation.

Explain to learners that the reduction of pyruvate to lactate is common in many bacteria. Highlight that these reactions are similar in widely different species of organism.

Online http://www.brianmac.demon.co.uk/oxdebit.htm Textbooks/Publications King p.84 Siddiqui p.101 Past Papers Paper 43, June 2013, Q4 (b)

http://www.brianmac.demon.co.uk/oxdebit.htm

http://www.brianmac.demon.co.uk/oxdebit.htm


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12.2.l explain how rice is adapted to grow with its roots submerged in water in terms of tolerance to ethanol from respiration in anaerobic conditions and the presence of aerenchyma Key concepts Organisms in their environment

Remind learners of xerophytes and adaptation to survival in arid conditions (7.2.f) and introduce rice as a plant adapted to survive with its roots submerged in water, which has little oxygen. (W) (Basic)

Explain that an ethanol build-up is toxic to yeast cells and that plant cells also produce ethanol when in anaerobic conditions. o Agree that continuous or prolonged anaerobic conditions as experienced

by rice when it is growing in flooded fields means that root cells need to be tolerant to ethanol. (W) (Basic)

Check learner understanding of the terms used in the learning objective: submerged and tolerance. (W) (Basic)

Learners use a light microscope to observe aerenchyma in root and stem sections of prepared slides. (I) (Basic)

To summarise, learners list and explain the features that make rice adapted to grow with roots that are submerged in water, and explain why most plants cannot survive when their roots are submerged in water. (F)

Online http://plantsinaction.science.uq.edu.au/edition1/?q=content/18-1-2-adaptive-responses-waterlogging www.biologymad.com/resources/Crop%20Plants.pps Past Papers Paper 41, Nov 2011, Q4 (a)(b) Paper 42, June 2013, Q10 (b)

12.2.j distinguish between respiration in aerobic and anaerobic conditions in mammalian tissue and in yeast cells, contrasting the relative energy released by each (a detailed account of the total yield of ATP from the aerobic respiration of glucose is not required) Key concepts Biochemical processes

Learners suggest what is meant by respiration: brainstorm ideas such as: the release of energy from food; the production of ATP; ATP for use by the cell; the process occurs in the cell. o Expand the discussion to distinguish between aerobic respiration and

respiration in anaerobic conditions. (W) (Basic)

Emphasise that most of the ATP is synthesised as a result of oxidative phosphorylation, requiring the reduced coenzymes from the link reaction and Krebs cycle (compare with the 2ATPs produced without oxygen). (W) (Basic)

Learners make notes comparing respiration in aerobic and anaerobic conditions. (W) (Basic)

Note

‘Balance sheets’ are not required. There are different totals for ATP production in aerobic respiration, varying from 32, to 36, to 38 in older text books. In more recent texts, the estimate of ‘1NADH = 3ATP’ is now seen as approximately 1NADH = 2.5ATP (also 1FADH = 1.5ATP).

Textbooks/Publications Jones, Fosbery, Taylor, Gregory, has on page 205 (2007), or on page 277 (2013), a balance sheet of ATP use and synthesis. This could be used to give learners an idea of the difference in relative energy released. Past Papers Paper 41, June 2011, Q7 (b)(ii) Paper 41, Nov 2011, Q6 (c)

12.2.h carry out investigations to determine

Remind learners that yeast is not a plant but a fungus. Emphasise that yeast respires aerobically and in anaerobic conditions. (W) (Basic)

http://plantsinaction.science.uq.edu.au/edition1/?q=content/18-1-2-adaptive-responses-waterlogging



http://www.biologymad.com/resources/Crop%20Plants.pps



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the effect of factors such as temperature and substrate concentration on the rate of respiration of yeast using a redox indicator (e.g. DCPIP or methylene blue) Key concepts Biochemical processes, Organisms in their environment, Observation and experiment

Explain that redox dyes are used as indicators of hydrogen transfer and in investigations can be used as artificial hydrogen acceptors to provide a visual check on the rate of respiration (the reduction of NAD or FAD cannot be ‘seen’). (W) (Basic) o State that methylene blue is blue in the oxidised state (without hydrogens)

and turns colourless as hydrogens are accepted and it becomes reduced. (W) (Basic)

o With this knowledge, small groups can be set the task of planning an appropriate investigation to carry out. (G) (Challenging)

Note

These investigations are a good opportunity to develop planning skills.

Experiments with yeast and anaerobic respiration require the substrate solution (e.g. glucose) to be boiled (to remove oxygen) and cooled.

12.1.f explain the relative energy values of carbohydrate, lipid and protein as respiratory substrates and explain why lipids are particularly energy-rich Key concepts Biochemical processes

Learners recall the overall equation for aerobic respiration and understand how it balances. (W) (Basic)

Explain that many cells can use other respiratory substrates, such as other sugars, lipids and proteins, and that different substrates have different energy values per unit mass. (W) (Basic)

Reflect back to 12.1.e to remind learners about the importance of supplying hydrogen to the ETC for electron flow and the release of energy for ATP production.

Learners consider ratios of C, H and O, to explain and note down the relative energy values of proteins, carbohydrates and lipids, noting that lipids, with proportionately more hydrogen per g of substrate, will yield more energy. (W) (I) (Basic)

Note

Knowledge of how the energy values are obtained is not required (see learning resources / endorsed textbooks for background information).

Online http://mutuslab.cs.uwindsor.ca/schurko/animations/bombcal/animation4.htm

12.1.g define the term respiratory quotient (RQ) and determine RQs from equations for respiration

Learners write out the definition of respiratory quotient and the formula to use when calculating RQ values. o Explain that volumes or moles or molecules can be used but for any one

calculation they should not be mixed.

Online http://www.biologymad.com/master.html?http://www.biologymad.com/PhotosynResp/PhotosynResp.htm

http://mutuslab.cs.uwindsor.ca/schurko/animations/bombcal/animation4.htm



http://www.biologymad.com/master.html?http://www.biologymad.com/PhotosynResp/PhotosynResp.htm




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Key concepts Biochemical processes, Organisms in their environment

o Learners calculate the RQ value for glucose. (W) (I) (Basic)

When provided with equations, learners calculate the RQs for named substrates. (P) (I) (Basic) (Challenging) o Learners construct a summary table for carbohydrates, proteins and lipids

(approximate values). (I) (Basic) o Learner explain the link between high RQ values and anaerobic

respiration. (I) (Basic)

Learners try SAQ 15.8, in Jones, Fosbery, Taylor, Gregory (2007), to calculate an RQ for a fatty acid. (I) (Challenging)

Textbooks/Publications In Jones, Fosbery, Taylor, Gregory, pages 208-209 (2007), or page 281 (2013), explains respiratory quotient and has worked examples. Past Papers Paper 43, Nov 2012, Q8 (c)

12.2.m carry out investigations, using simple respirometers, to measure the effect of temperature on the respiration rate of germinating seeds or small invertebrates Key concepts Observation and experiment

Explain how to use a simple respirometer to determine the rate of oxygen uptake and rate of carbon dioxide production. (W) (Basic)

Discuss the benefits of using thermostatically-controlled water baths to maintain a constant temperature. o Learners suggest other ways of maintaining a constant temperature, with

peer evaluation of the method. (P) (I)

Practical booklet 7 involves using a simple respirometer and provides opportunity for data analysis and planning for Paper 5. Learners plan an investigation to find the optimum temperature for respiration. Learners swap and carry out a partners plan exactly as written, each to provide their partner with an evaluation of the plan. (P) (I) (Challenging)

Note

You may wish to save time and also carry out the requirement of 12.1.h.

Simple designs, using a single syringe and capillary tubing (as in Practical booklet 7) are far more sensitive to temperature and require minimal handling.

The simple respirometers are more reliable in yielding results than the modifications of the Barcroft respirometer, usually given in practical guides.

Temperature compensation by having two tubes linked by a manometer results in well controlled experiments, but introduces potentially leaky joints.

A teacher demonstration of a temperature-compensated respirometer is advisable, so learners see both types.

Practical booklet 7 Online http://www.phschool.com/science/biology_place/labbench/lab5/features.html http://www.biologymad.com/master.html?http://www.biologymad.com/PhotosynResp/PhotosynResp.htm Textbooks/Publications King p.80-83 Siddiqui p.101-103

12.1.h Learners carry out an investigation to measure RQ using the simple Practical booklet 7

http://www.phschool.com/science/biology_place/labbench/lab5/features.html







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carry out investigations, using simple respirometers, to determine the RQ of germinating seeds or small invertebrates (e.g. blowfly larvae) Key concepts Observation and experiment

respirometers (planning skills may be developed here), o e.g. learners measure carbon dioxide production and oxygen absorption

by germinating seeds, and calculate RQ. This has the potential to develop abilities evaluating investigations. (I) (Challenging)

Online http://www.biologymad.com/master.html?http://www.biologymad.com/PhotosynResp/PhotosynResp.htm http://www.phschool.com/science/biology_place/labbench/lab5/features.html Textbooks/Publications King p.80-83 Siddiqui p.101-103








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Unit 10: Mammalian physiology, control and coordination


Learners should have a good understanding of cell structure and the structure of a cell surface membrane. They should have an appreciation of the role of the various components, particularly the role of glycoproteins as receptors in cell signalling and of membrane transport proteins. They should understand the concept of water potential and have good knowledge of transport mechanisms across membranes, including facilitated diffusion and active transport from Unit 2. Context

This unit builds on the key concept of cells as the basic units of life to consider how mammals, as multicellular organisms, control and coordinate activities and how homeostatic mechanisms enable a balance to be maintained. The maintenance of homeostatic mechanisms for healthy functioning, such as in controlling blood glucose concentrations, extends learner understanding of non-infectious disease. Cell structure, cell membranes, transport across membranes and the mammalian circulatory system are topics covered at AS Level that are an important foundation for the learning objectives studied in this unit. A study of dipsticks, biosensors and the contraceptive pill highlights the dependence of humans on biotechnology: biotechnology results from observation, enquiry and experiment, a key concept. The examples studied here extend learner knowledge from those already covered in Unit 8. Outline

This unit begins by highlighting the importance of responding to external and internal stimuli with effective control and coordination by the nervous system and by the endocrine system. The structure and function of the motor and sensory neurone is covered and there is a detailed study of the transmission of nerve impulses, including transmission across the synapse and the neuromuscular junction, followed by a consideration of the sliding filament theory of muscle contraction. Learners consider the involvement of the nervous and endocrine systems in homeostatic mechanisms and discuss the role of negative feedback. Thermoregulation, osmoregulation and blood glucose regulation exemplify the importance of homeostasis in mammals. The production of urea and the role of the kidney in the excretion of nitrogenous wastes are described. Detail of the control of blood glucose concentration and water content (by the kidney) illustrates the concept of homeostasis. Biotechnological applications are included by considering the use of dipsticks and biosensors in the detection of glucose in the blood and urine, and of protein and ketones in urine. The unit concludes with a study of the menstrual cycle and the role of hormones in the cycle, which leads to a description of the contraceptive pill. Teaching time



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15.1.a compare the nervous and endocrine systems as communication systems that co-ordinate responses to changes in the internal and external environment (see 14.1.a) and 14.1.b) Key concepts Cells as the units of life, Organisms in their environment

Discuss the need for communication between organs in a multicellular organism and how activities need to be controlled and coordinated. (W) (Basic)

Use a brainstorm session to gauge learner knowledge and to discuss the main features of each. As individuals make suggestions and agree whether they are referring to the nervous or endocrine system. (W) (Basic) o Learners note down that the two systems are for control, coordination and

internal communication, and that they can interrelate and affect each other. (W) (Basic)

Learners research and give definitions of the terms: stimulus, receptor, effector, control centre and response. (I) (Basic)

Learners list the features of an endocrine gland (an organ or tissue), with teacher guidance. (W) (I) (Basic) o Learners sketch endocrine glands onto a cut-out / diagram of a body and

name the hormones that they secrete. Fill in any gaps in knowledge, mentioning those particularly that are in this syllabus. (I) (Basic)

o Learners name the target cells / tissues of each hormone, consolidating understanding of hormones acting at a distance from their origin and at particular sites of action. (W) (Basic)

Focus on the nervous system and ask what the equivalent to the hormones would be to enable coordination. Encourage learners to use the terms nerve impulses or impulses. (W) (Basic)

Continue the discussion for learners to name the brain as the main control centre, and muscles and glands, including endocrine glands, as effectors.

Divide the class into two. One half participates in a group discussion to suggest examples of internal changes in organisms, stating for each one: the organs / systems that are affected; receptor(s); communication method; effector(s); and response(s). The other half suggests examples of changes in external environment. The two groups come together to share ideas. (W) (G) (Basic).

Note

It will be noted that both systems involve negative feedback – a verbal clarification of this mechanism is sufficient as learners will define the term

CD-ROM Bioscope – has images of nerves (LS and TS). Online http://www.udel.edu/Biology/Wags/histopage/colorpage/cp/cp.htm http://www.s-cool.co.uk/a-level/biology/nervous-and-hormonal-control Textbooks/Publications Bio Factsheet 38: Animal hormones and hormone action. King p. 151-152 Siddiqui p.164-167, 171 Past Papers Paper 41, June 2011, Q9 (a)

http://www.udel.edu/Biology/Wags/histopage/colorpage/cp/cp.htm

http://www.udel.edu/Biology/Wags/histopage/colorpage/cp/cp.htm

http://www.s-cool.co.uk/a-level/biology/nervous-and-hormonal-control




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later.

Understanding of all terms will be consolidated as learners cover specific examples within the unit.

15.1.b describe the structure of a sensory neurone and a motor neurone Key concepts Cells as the units of life

Explain that nerves are composed of many specialised nerve cells, neurones, held by connective tissue. (W) (Basic)

Learners draw, label and annotate a sensory and a motor neurone. (I) (Basic) o Learners compare the diagrams with electron micrographs. (I)

(Challenging)

Learners explain how the structure of the neurone is related to its function (or wait until after 15.1.d has been covered). (H) (Basic)

Learners complete unlabelled and incomplete diagrams (the diagrams could lack nuclei, myelin sheaths and synaptic knobs). (F)

Online http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookNERV.html#The%20Neuron http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Neurons.html Past Papers Paper 43, Nov 2011, Q9 (a)

15.1.c outline the roles of sensory receptor cells in detecting stimuli and stimulating the transmission of nerve impulses in sensory neurones (a suitable example is the chemoreceptor cell found in human taste buds) Key concepts Cells as the units of life, Organisms in their environment

Explain the difference between a sensory receptor cell and a sense organ, e.g. tongue = organ of taste; taste cells are chemoreceptors (sensory receptor cells) found in clusters called taste buds. (W) (Basic)

Explain that the different forms of energy arriving at the sensory receptor get converted (transduced) into electrical energy of the nerve impulse. o State that all sensory receptors are transducers. (W) (Basic)

Learners research and list the different sensory receptors in humans and name the forms of energy received by each receptor. (P) (I) (Basic)

Describe the sensory neurone with a resting potential and explain how a stimulus leads to membrane depolarisation and impulse transmission. o State that depolarisation causes an action potential to be generated and

explain that details are covered later. (W) (Challenging)

Choose for example, chemoreceptors as sensory receptors and state that they detect specific molecules or classes of molecule. o Learners suggest internal and external stimuli that are detected by

chemoreceptors and give examples of responses (e.g. the difference between harmful / toxic substances taken into the mouth and food). (W) (Basic)

Show learners a diagram of a sensory receptor cell / chemoreceptor and explain that a taste cell has contact with a sensory neurone. o Explain that the binding of molecules to receptors on the cell surface

Online http://faculty.washington.edu/chudler/twopt.html http://www.answers.com/topic/taste-and-smell Textbooks/Publications King p.180-183 Past Papers Paper 41, Nov 2011, Q11 (a)

http://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookNERV.html#The%20Neuron



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Neurons.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Neurons.html

http://faculty.washington.edu/chudler/twopt.html

http://faculty.washington.edu/chudler/twopt.html

http://www.answers.com/topic/taste-and-smell

http://www.answers.com/topic/taste-and-smell


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membrane (many microvilli) of the taste cell leads to depolarisation, which is passed onto the sensory neurone and the control centre.

o Learners state the type of transduction that has occurred. (W) (Challenging)

Learners produce a diagram of a sensory receptor cell, showing synapses with dendrites of a sensory neurone. o Learners annotate the sequence of events occurring from the detection of

a stimulus to an impulse being transmitted along the sensory neurone. (I) (Challenging)

Introduce the terms receptor potential and all-or-nothing law/rule, either by teacher-led discussion or by textbook/internet research. (W) (I) (Challenging)

Practical: learners carry out experiments to investigate touch, temperature and pain receptors in the skin. (P) (I) (Basic)

Note

Explain to learners that some sensory receptors are also sensory neurones, while others are specialist receptor cells that synapse with sensory neurones.

Learners should feel confident applying the principles of the process to other examples of sensory receptor cells.

15.1.d describe the functions of sensory, relay and motor neurones in a reflex arc Key concepts Cells as the units of life

Explain that a reflex arc is the neural pathway behind a reflex action. o Introduce the relay neurone before asking learners to draw and annotate a

reflex arc. (W) (I) (Basic)

Practical: learners look at prepared slides of cross-sections of the spinal cord to identify features. (I) (Basic)

Practical: learners carry out an experiment on a particular reflex action. o For each, learners draw a reflex arc and annotate to show the function of

the neurones. (F)

Learners research examples of reflexes using the spinal cord and the brain, detailing: stimulus; receptor; effector; and response. (H) (Basic) o Learners share examples with the class. (W) (Basic)

Note

Point out that some reflex actions (e.g. the pupil reflex) involve the brain rather than the spinal cord.

Online http://www.sumanasinc.com/webcontent/animations/content/reflexarcs2.html http://www.sciencejoywagon.com/explrsci/media/reflex.htm http://www.intelligencetest.com/reflex/index.htm Textbooks/Publications Bio Factsheet 58: Reflex action

http://www.sumanasinc.com/webcontent/animations/content/reflexarcs2.html



http://www.sciencejoywagon.com/explrsci/media/reflex.htm

http://www.sciencejoywagon.com/explrsci/media/reflex.htm

http://www.intelligencetest.com/reflex/index.htm

http://www.intelligencetest.com/reflex/index.htm


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15.1.e describe and explain the transmission of an action potential in a myelinated neurone and its initiation from a resting potential (the importance of sodium and potassium ions in impulse transmission should be emphasised) Key concepts Cells as the units of life, Biochemical processes

Describe an action potential as a rapid, temporary change in a membrane potential, explaining that this acts as a ‘booster’ to ensure the impulse (see 15.1.a) travels the distance. (W) (Basic)

Explain the potential difference across the neurone membrane (mention also the presence of large anions inside the axon). o Build on AS Level knowledge to discuss how the resting potential is

maintained (membrane polarised) by the sodium-potassium pump. o Explain the presence of non-voltage gated channels and facilitated

diffusion of K+ outwards.

o Describe the voltage-gated channels (NaV and KV) specific to the two ions (which are closed). (W) (Challenging)

Learners set the scene by drawing an annotated diagram of the axon at rest / polarised. (I) (Basic)

Revisit understanding of ‘partially permeable’ and discuss ‘relatively impermeable’ and ‘relatively permeable’. o Explain that open voltage-gated channels will increase membrane

permeability to the ion concerned (Na+

or K+). (W) (Basic)

Display diagrams showing the outside and the inside of a neurone – one at a time or project an animation – to explain what occurs when depolarisation in the previous section increases the membrane voltage above a threshold value (relate back to all-or-nothing from 15.1.c). Include diagrams for: o Depolarisation: explain how the open NaV channels stimulate more

channels to open (further depolarisation = positive feedback); action potential = the large change in membrane potential.

o Repolarisation: Describe the changes occurring to NaV and KV channels and movement of ions.

o (Temporary) undershoot: explain that the membrane is more permeable to K

+ than at rest, until their channels close.

o Refractory period: explain how closed voltage-gated channels and action of the sodium-potassium pump restores the resting potential.

o At each stage, learners suggest permeability states to the different ions, highlighting the slower-to-react KV channels and the importance of inactivity of NaV channels. (W) (Challenging)

Learners prepare the axes on graph paper and sketch the changes to potential as each stage is discussed. (I) (Basic)

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=40 http://www.biologymad.com/NervousSystem/nerveimpulses.htm http://outreach.mcb.harvard.edu/animations/actionpotential_short.swf Past Papers Paper 41, Nov 2011, Q11 (a)



http://www.biologymad.com/NervousSystem/nerveimpulses.htm

http://www.biologymad.com/NervousSystem/nerveimpulses.htm

http://outreach.mcb.harvard.edu/animations/actionpotential_short.swf

http://outreach.mcb.harvard.edu/animations/actionpotential_short.swf


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o Learners annotate the graph, explaining what is occurring at different time points: resting potential, rising and falling phases of action potential, undershoot, refractory period. (F)

Discuss how Na+ entering the axon establishes a local circuit between this

and the negatively charged resting potential in the area ahead. (W) (Challenging) o Learners suggest how current flow changes membrane permeability to

Na+ to cause self-propagation of the action potential, and how/why this is

in one direction only. (W) (Challenging)

Discuss the two phases of the refractory period. (W) (Challenging)

Learners draw four diagrams of the same section of axon (e.g. draw a simple cylinder to show the outside and inside of the neurone), headed ‘resting potential’ ‘depolarisation’ ‘repolarisation’ ‘refractory period’. o Learners draw on the location or movement of Na

+ and K

+, giving a

summary under each diagram. (I) (Challenging)

Learners explain the difference between the following: absolute refractory period and relative refractory period; resting potential and action potential; polarised and depolarised; impulse and action potential. (H) (Challenging)

Note

There are no action potentials in short neurones as current flow is sufficient to ensure the impulse travels the short distance.

15.1.f explain the importance of the myelin sheath (saltatory conduction) in determining the speed of nerve impulses and the refractory period in determining their frequency Key concepts Cells as the units of life

Learners use resources to draw a labelled, annotated diagram showing transmission of an action potential in a myelinated axon. o Learners add explanations to show how saltatory conduction is brought

about, noting the high concentration of voltage-gated channels at the nodes.

o Learners note how saltatory conduction has a great effect on speed of transmission of impulses. (I) (Challenging)

Learners link the inactivated sodium voltage-gated channels during the falling phase and part of the undershoot of the action potential (see 15.1.e), to an inability to trigger another action potential immediately if a second depolarisation arrives. o Learners annotate their action potential graph. (W) (I) (Challenging)

Online http://www.bu.edu/histology/m/t_electr.htm http://www.bu.edu/histology/p/21201loa.htm http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMSchwannE.html Past Papers Paper 41, June 2011, Q6 (c)

http://www.bu.edu/histology/m/t_electr.htm

http://www.bu.edu/histology/m/t_electr.htm

http://www.bu.edu/histology/p/21201loa.htm

http://www.bu.edu/histology/p/21201loa.htm

http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMSchwannE.html




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Learners interpret diagrams and electron micrographs of an axon with a myelin sheath, identifying Schwann cells and nodes of Ranvier. o Learners study electron micrographs of unmyelinated axons and make

comparisons. (I) (Basic)

15.1.g describe the structure of a cholinergic synapse and explain how it functions, including the role of calcium ions Key concepts Cells as the units of life, Biochemical processes

Learners copy out a definition of a synapse. Explain they will study a cholinergic synapse, which is a chemical synapse. (W) (I) (Basic)

Learners draw and label a diagram of a synapse. (I) (Basic)

Learners compare electron micrographs and diagrams of synapses. (I) (Basic)

Remind learners of links with AS Level before outlining events in synaptic transmission: for example, mitochondria, exocytosis, diffusion, membrane proteins, hydrolysis catalysed by enzymes. (W) (Basic)

One learner makes the first statement in the sequence of events in synaptic transmission and chooses another learner to describe the next event, and so on. (G) (Basic)

A learner chooses a diagram in the sequence and a partner describes what is occurring and what will happen next. (P) (Basic)

Learners rearrange a set of diagrams to arrive at the correct sequence of events in synaptic transmission. (F) (Basic) o Learners add annotations to the sequenced diagrams and if necessary

make additional bullet points. (F) (Challenging)

Extension: discuss the effects of drugs on the transmission across the synapse and show learners how to apply knowledge and understanding to new situations. (W) (Basic)

Note

Explain that there are other types of chemical synapses, and mention electrical synapses.

Online http://www.sumanasinc.com/webcontent/animations/content/synaptictransmission.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Drugs.html Textbooks/Publications Bio Factsheet 20: Nerves and synapses Bio Factsheet 155: Answering exam questions on neurones and synapse Past Papers Paper 43, Nov 2011, Q9 (b)

15.1.h outline the roles of synapses in the nervous system in allowing transmission in one direction and in allowing connections between one

Learners suggest and note down which features ensure one-way transmission of impulses across a synapse (vesicles with transmitter substance only found in the presynaptic neurone; specific receptor proteins only located on the postsynaptic membrane). (W) (I) (Basic)

Discuss the fact that one neurone can have many synapses relating to it, thus

Online http://www.skoool.ie/skoool/examcentre_sc.asp?id=2879 Textbooks/Publications

http://www.sumanasinc.com/webcontent/animations/content/synaptictransmission.html



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Drugs.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Drugs.html

http://www.skoool.ie/skoool/examcentre_sc.asp?id=2879

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neurone and many others (summation, facilitation and inhibitory synapses are not required) Key concepts Cells as the units of life

allowing interconnection of numerous nerve pathways. (W) (I) (Basic)

Background: discuss the benefits of interconnection (a stimulus can lead to a range of responses; can collect more information; excitatory and inhibitory synapses provide more flexibility in response, hence a wider range of behaviour. (W) (Basic)

Extension: learners carry out some simple investigations into learning that involves synapses. (P) (I) (Challenging)

King p.202-205. Past Papers Paper 41, Nov 2012, Q1 (b(i)

15.1.i describe the roles of neuromuscular junctions, transverse system tubules and sarcoplasmic reticulum in stimulating contraction in striated muscle Key concepts Cells as the units of life, Biochemical processes

Learners study one or more labelled diagrams and establish that: striated muscle is voluntary; skeletal muscle, the multinucleate cells are also known as muscle fibres and contain a bundle of myofibrils. o Learners note that the cell surface membrane of the muscle fibre is

termed sarcolemma, and the cytoplasm is sarcoplasm. o Explain that the sarcoplasmic reticulum is in contact with the myofibrils

and is similar to SER (Unit 1) and that transverse system tubules are infoldings of the cell surface membrane. (W) (Basic)

Learners label a diagram of a neuromuscular junction, adding labels using resources and knowledge of synaptic transmission. o Learners note that the neuromuscular junction is a form of synapse that is

necessary to allow the effector to respond. (I) (Basic)

Learners sort cards containing details of the sequence of events occurring following depolarisation at the synaptic terminal of the motor neurone (end with calcium ion release by the sarcoplasmic reticulum – see 15.1.k). o Learners make notes, highlighting roles of the named items in the learning

objective. (P) (I) (Challenging)

Extension: learners research myasthenia gravis (Unit 11) and compare a normal and a myasthenic neuromuscular junction. (H) (Challenging)

Online http://www.bu.edu/histology/p/21501ooa.htm http://www.getbodysmart.com/ap/muscletissue/fibers/sr/tutorial.html Textbooks/Publications Bio Factsheet 190: Neuromuscular junctions

15.1.j describe the ultrastructure of striated muscle with particular reference to sarcomere structure Key concepts Cells as the units of life

Discuss the idea of a sarcomere (see 15.1.i diagrams) as the basic unit of contraction, a repeating unit of a pattern made by thick and thin protein filaments. (W) (Basic)

Learners label and annotate diagrams of the same sarcomere (i) relaxed, (ii) contracting, and (iii) fully contracted, to prepare for 15.1.k. o Learners compare electron micrographs with their diagram. (I) (Basic)

Online http://www.bu.edu/histology/p/21601ooa.htm



http://www.getbodysmart.com/ap/muscletissue/fibers/sr/tutorial.html

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15.1.k explain the sliding filament model of muscular contraction including the roles of troponin, tropomyosin, calcium ions and ATP Key concepts Biochemical processes

Explain the sliding filament model while learners add labels to prepared diagrams. o Discuss the role of the released calcium ions in binding to sites on

troponin and shifting the position of tropomyosin to expose the myosin binding sites. (W) (Basic)

Learners annotate their diagrams from 15.1.j. (I) (Challenging)

As a whole group, the first member states the first event occurring, ‘depolarisation of the membrane of the synaptic terminal’ and then chooses the next member of the group to continue the ‘story’. (W) (Challenging)

Learners produce a written account, or a flow chart diagram, summarising the sequence of events occurring from the arrival of an action potential at the synaptic terminal of the motor neurone to the contraction of the sarcomere. (F)

Textbooks/Publications Bio Factsheet 46: Muscles.

14.1.a discuss the importance of homeostasis in mammals and explain the principles of homeostasis in terms of internal and external stimuli, receptors, central control, co-ordination systems, effectors (muscles and glands) Key concepts Cells as the units of life, Organisms in their environment

Learners write an explanation of what is meant by homeostasis. o Explain that they should think of main ideas and use appropriate

terminology (e.g. give choice as below). Maintenance of, an internal / a cellular, environment … at a constant level / set point / norm / normal level / stable level or

within normal limits … despite changes / fluctuations in the internal or external environment

… using negative feedback control mechanisms … so that cells can function efficiently. (I) (Basic)

Learners suggest the different parameters or physiological factors that should be kept at / around a set point (e.g. temperature, blood glucose concentration, blood pH / carbon dioxide concentration, water balance / water potential, metabolic wastes) and explain the importance of maintaining the balance. o Encourage use of the terms negative feedback (defined in 14.1.b)

receptors and effectors. (W) (Basic)

Learners use separate cards (limit 10-12) to write out definitions and features of the terms stimulus, receptor, effector, control centre, response. o Learners swap with a partner, who can write down the relevant term that

is being described. (P) (I) (Challenging)

Online http://www.biologymad.com/master.html?http://www.biologymad.com/Homeostasis/Homeostasis.htm

14.1.b Learners write out the simple definition using resources and then qualify Online

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define the term negative feedback and explain how it is involved in homeostatic mechanisms Key concepts Cells as the units of life

further after discussion: o Physiological processes or a changing external environment can cause

variation from the set point. o A mechanism brings the internal environment back to the set point, or

small oscillations about the set point. o Negative feedback always involves a receptor and effector and often

involves a control centre. (W) (I) (Challenging)

Using a named example, learners draw a flow chart to summarise homeostatic control and negative feedback, showing the named receptor(s), effector(s) and control centre (if present). (H) (Basic)

Learners are provided with a paragraph describing a named example of homeostatic control and construct an annotated diagram as a summary. (F)

http://www.biology-online.org/4/1_physiological_homeostasis.htm http://scienceaid.co.uk/biology/humans/homeostasis.html http://science.jrank.org/pages/3365/Homeostasis.html Textbooks/Publications Bio Factsheet 28: Feedback control mechanisms Bio Factsheet 161: Negative Feedback Mechanisms

14.1.c outline the roles of the nervous system and endocrine system in co-ordinating homeostatic mechanisms, including thermoregulation, osmoregulation and the control of blood glucose concentration Key concepts Cells as the units of life, Biochemical processes

Learners write a paragraph explaining what the two systems have in common and then construct a table of the differences. (I) (Challenging)

Learners to research the difference between: excretion and secretion; an endocrine gland and an exocrine gland. (H) (Basic)

Using resources, learners outline the involvement of the nervous system and endocrine system in each of the named mechanisms, including naming, and describing the role of, any hormones. (I) (Basic)

Note

There are close links to 15.1.a.

The research on osmoregulation and blood glucose concentration is useful for later studies.

Online http://www.abpischools.org.uk/page/modules/homeostasis_sugar/sugar2.cfm

14.1.d describe the deamination of amino acids and outline the formation of urea in the urea cycle (biochemical detail of the urea cycle is not required) Key concepts Biochemical processes

Learners suggest the distinction between excretion and egestion. (W) (Basic)

Describe how deamination removes the toxic part of an amino acid molecule, forming highly toxic ammonia, and leaves a useful keto acid (chemical energy for respiration or conversion for energy storage). o Explain that in many terrestrial animals the ammonia is immediately

converted to the less toxic urea. (W) (Basic)

Learners annotate an outline diagram of deamination and the urea (ornithine) cycle as you provide additional information, including: takes place in the liver;

Online http://www.ilng.in/pdf/mtg_bio_final.pdf http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/U/UreaCycle.html Textbooks/Publications Bio Factsheet 59: Excretion.

http://www.biology-online.org/4/1_physiological_homeostasis.htm



http://scienceaid.co.uk/biology/humans/homeostasis.html

http://scienceaid.co.uk/biology/humans/homeostasis.html

http://science.jrank.org/pages/3365/Homeostasis.html

http://science.jrank.org/pages/3365/Homeostasis.html

http://www.abpischools.org.uk/page/modules/homeostasis_sugar/sugar2.cfm



http://www.ilng.in/pdf/mtg_bio_final.pdf

http://www.ilng.in/pdf/mtg_bio_final.pdf

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/U/UreaCycle.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/U/UreaCycle.html


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enzyme controlled; ATP required; urea transported dissolved in the blood. (I) (Basic)

Extension: learners draw a molecule of urea highlighting that it is a small organic compound (useful for later work on the kidney). (W) (Basic)

Note

Explain that amino acids are not stored in the body.

14.1.e describe the gross structure of the kidney and the detailed structure of the nephron with its associated blood vessels using photomicrographs and electron micrographs Key concepts Cells as the units of life

Agree with learners the location of their kidneys. (W) (Basic)

Show learners, on a whole kidney, what is meant by transverse and longitudinal sections before learners identify structures from images. o Learners hold up to the light the prepared slides of rat kidney to show the

shape of the entire kidney in LS or TS, and the areas of cortex and medulla. (W) (I) (Challenging)

Learners dissect (e.g. from a sheep), or use images of, a whole kidney to make annotated drawings of the external appearance and a section through the kidney. (I) (Challenging)

Go through a diagram of nephron structure, including the associated blood vessels. Refer also to the high blood pressure in the renal artery. o Explain that the venous system does not begin immediately after the

glomerulus, and that there is a dense capillary network serving the nephrons. (W) (Basic)

o Learners label and annotate the diagram. (I) (Basic)

Note

If a kidney is dissected, learners can trace the renal artery, renal vein and ureter, and follow the blood vessels into the cortex.

CD-ROM Bioscope – has images of kidney sections. Online http://www.histology.leeds.ac.uk/urinary/kidney.php http://library.med.utah.edu/WebPath/RENAHTML/RENALIDX.html http://www.cie.org.uk/cambridge-for/teachers/order-publications/ Textbooks/Publications King p.155-156 Siddiqui p.191-194 Bio Factsheet 1: The kidney: excretion and osmoregulation Past Papers Paper 32, June 2011, Q2 Paper 41, June 2012, Q10 (a)

14.1.f describe how the processes of ultrafiltration and selective reabsorption are involved with the formation of urine in the nephron

For an overview, learners annotate a large diagram as you outline the processes occurring in each region. (W) (I) (Basic)

Explain how sufficient pressure is present for ultrafiltration. o Discuss how the presence of the plasma proteins remaining in the blood

has some effect on water potential and the filtration process. (W) (Basic)

Learners annotate diagrams to explain how the structure of the Bowman’s

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/K/Kidney.html www.biologyinmotion.com/nephron/index.html http://www.biologymad.com/resource

http://www.histology.leeds.ac.uk/urinary/kidney.php

http://www.histology.leeds.ac.uk/urinary/kidney.php

http://library.med.utah.edu/WebPath/RENAHTML/RENALIDX.html

http://library.med.utah.edu/WebPath/RENAHTML/RENALIDX.html

http://www.cie.org.uk/cambridge-for/teachers/order-publications/

http://www.cie.org.uk/cambridge-for/teachers/order-publications/

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/K/Kidney.html


http://www.biologyinmotion.com/nephron/index.html


http://www.biologymad.com/resources/kidney.swf


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capsule and glomerulus allows the process of ultrafiltration to occur. o Explain the role of the basement membrane as the true dialysing filter. (I)

(Challenging)

Learners make a list of the components of glomerular filtrate and list the components of blood that are too large for ultrafiltration. (I) (Basic)

Learners interpret tables showing the concentration of various substances in the blood plasma and the glomerular filtrate to make comparisons. (I) (Basic)

Learners annotate diagrams of selective reabsorption in the proximal convoluted tubule (PCT), with teacher-led prompts o To consolidate, learners make bullet point notes using resources. (I)

(Challenging)

Learners produce a summary listing the mechanisms of transport used in selective reabsorption and the substances that are transported. (I) (Basic)

Learners explain how the structure of the cuboidal epithelial cells of the PCT are suited to their function. (H) (F) (Challenging)

Background: learners research the principles behind kidney dialysis. (I) (Challenging)

Note

For the overview diagram, explain that in the loop of Henle most water is reabsorbed, and that the outward movement of sodium (and chloride) ions into the interstitial fluid occurs to create a very low water potential. No details of the mechanism or the countercurrent multiplier are required.

s/kidney.swf http://www.sumanasinc.com/webcontent/animations/content/kidney.html Textbooks/Publications Bio Factsheet 1: The kidney: excretion and osmoregulation Bio Factsheet 59: Excretion Bio Factsheet 150: Answering Exam Questions on the Kidney Past Papers Paper 41, June 2012, Q10 (b)

14.1.g describe the roles of the hypothalamus, posterior pituitary, ADH and collecting ducts in osmoregulation Key concepts Cells as the units of life, Biochemical processes

Learners recall from 14.1.c and AS Level why it is important to control the water content of the blood (refer to water potential gradients and osmosis). o Learners discuss the consequences and the conflict between maintaining

a constant volume of blood and maintaining constant water potential, e.g. when someone has a meal high in salt. (W) (Basic)

Learners rearrange a set of linked, sequential statements to give a description of the roles in osmoregulation of the hypothalamus, posterior pituitary; ADH and collecting duct (CD). Include one statement to show the role of the distal convoluted tubule (DCT). o Reminded learners that the surrounding (interstitial) fluid has a very low

water potential. (P) (I) (Challenging)

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/K/Kidney.html www.biologyinmotion.com/nephron/index.html http://www.biologymad.com/resources/kidney.swf http://www.sumanasinc.com/webcontent/animations/content/kidney.html Textbooks/Publications


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o Learners use the statements as the basis for their notes. (I) (Basic)

Learners are later given only a few of these statements to sequence and fill in the missing details. (F)

Learners produce a flow chart to show the negative feedback control of water in the blood. (H) (Basic)

As a summary, learners interpret data from tables or graphs to explain and relate concentrations of different substances in each part of the nephron. (I) (Challenging).

Bio Factsheet 1: The kidney: excretion and osmoregulation Bio Factsheet 59: Excretion Bio Factsheet 150: Answering Exam Questions on the Kidney

14.1.h explain how the blood glucose concentration is regulated by negative feedback control mechanisms, with reference to insulin and glucagon Key concepts Cells as the units of life, Biochemical processes

Learners suggest (i) why it is important for blood glucose concentration to be kept relatively constant, and (ii) why, in healthy people, oscillations around the norm concentration is inevitable. (W) (Basic)

Using resources, learners construct a table similar to the incomplete table below. (I) (Basic)

norm/set point of 90-120mg of glucose 100cm

-3 blood

increases above decreases below

stimulus detected by beta () cells pancreas

alpha () cells pancreas

hormone released insulin glucagon

main target tissues of hormone

liver and muscles (+adipose tissue)

liver

main effects of hormone

stimulates uptake of glucose ……………….. ……………………

stimulates breakdown of glycogen to glucose …………………….

final outcome blood glucose concentration decreases

blood glucose concentration increases

Learners describe the sequence of events occurring in the body after having a carbohydrate-rich meal (illustrating homeostasis). (H) (Basic)

Learners construct a flow chart to show negative feedback control of blood glucose concentration involving insulin and glucagon.

Online http://www.biologyreference.com/Bl-Ce/Blood-Sugar-Regulation.html http://www.mydr.com.au/gastrointestinal-health/pancreas-and-insulin Textbooks/Publications Bio Factsheet 145: Blood sugar and its control Past Papers Paper 43, Nov 2011, Q7

http://www.biologyreference.com/Bl-Ce/Blood-Sugar-Regulation.html

http://www.biologyreference.com/Bl-Ce/Blood-Sugar-Regulation.html

http://www.mydr.com.au/gastrointestinal-health/pancreas-and-insulin

http://www.mydr.com.au/gastrointestinal-health/pancreas-and-insulin


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o Learners add annotations or bullet points and include the terms homeostasis, stimulus, receptor, effector and negative feedback. (F)

Extension: learners investigate the effect of diabetes mellitus on the control of blood glucose concentration. Links: use of dipsticks, 14.1.k; insulin production by genetic engineering, 19.2.c. (H) (Basic)

Note

Accurate spelling is important: both glucagon and glycogen are terms used in this topic.

14.1.i outline the role of cyclic AMP as a second messenger with reference to the stimulation of liver cells by adrenaline and glucagon Key concepts Biochemical processes

Use a question and answer session to remind learners of membrane proteins that function as receptors and enzymes. o Explain that liver cells have different receptors to bind adrenaline and

glucagon. o Learners suggest why the hormones are unable to trigger directly

reactions within the cell (hydrophilic, do not enter cell). o Use a diagram to outline how binding causes production in the cytoplasm

of cyclic AMP, which then stimulates the enzymatic conversion of glycogen to glucose. (W) (Basic)

Learners write a paragraph to explain the difference between first and second messengers. (F)

Note

Muscle cells have receptors for adrenaline but not for glucagon.

Names of the specific receptors are not required.

Notes are not necessary at this point as a summary of 14.1.j will suffice

Online http://courses.washington.edu/conj/gprotein/cyclicamp.htm http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120109/bio48.swf::Action%20of%20Epinephrine%20on%20a%20Liver%20Cell

14.1.j describe the three main stages of cell signalling in the control of blood glucose by adrenaline as follows:

hormone-receptor interaction at the cell surface (see 4.1c))

formation of cyclic AMP which binds to kinase proteins

an enzyme cascade involving

Discuss the role of adrenaline so learners understand the need for a higher-than-normal blood glucose concentration. (W) (Basic)

Discuss the sequential process using diagrams. (W) (Challenging)

Learners annotate copies of the diagrams, highlighting how one event triggers the next: o Binding of adrenaline and activation of G (membrane) protein. o Enzyme-catalysed formation of cyclic AMP at the membrane and

consequential activation of kinase proteins. o Phosphorylation of enzymes involved in carbohydrate and lipid

Online http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120109/bio48.swf::Action%20of%20Epinephrine%20on%20a%20Liver%20Cell http://www2.estrellamountain.edu/faculty/farabee/BIOBK/biobookendocr.ht

http://courses.washington.edu/conj/gprotein/cyclicamp.htm


http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120109/bio48.swf::Action%20of%20Epinephrine%20on%20a%20Liver%20Cell












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activation of enzymes by phosphorylation to amplify the signal


metabolism, e.g. for the breakdown of glycogen to glucose-1-phosphate. (I) (Challenging)

Learners re-order statements to show the sequential process (F)

ml http://courses.washington.edu/conj/gprotein/cyclicamp.htm

14.1.k explain the principles of operation of dip sticks containing glucose oxidase and peroxidase enzymes, and biosensors that can be used for quantitative measurements of glucose in blood and urine Key concepts Biochemical processes, Observation and experiment

Remind learners how a dipstick is used to detect glucose and then explain the principles of operation before learners make notes. o Learners write out a worded reaction and explain why a reaction catalysed

by glucose oxidase will confirm the presence of glucose (enzyme specificity, Unit 1).

o Explain that peroxidases are used so that the hydrogen peroxide product reacts with a chemical (chromogen) that produces a coloured product. (W) (I) (Basic)

Practical: if available, learners compare Clinistix to Diastix. (W) (Basic)

Outline the operation of the biosensor by incorporating questions to link to AS Level topics: partially permeable membrane, diffusion of glucose molecules (from the blood sample), immobilised enzymes and specificity. o Discuss how the reaction needs to be detected, e.g. use of electrodes; a

decrease in oxygen; increase in hydrogen peroxide; production of gluconic acid.

o Learners explain how the digital read-out is proportional to the concentration of glucose in the sample. (W) (Challenging)

Discuss how dipsticks and portable devices to detect glucose and measure concentrations are considered great improvements for people with diabetes (compared to times before glucose biosensors and the Benedict’s tests. (W) (Basic)

Learners compare the use of glucose dipsticks and glucose biosensors, explaining advantages of each. (I) (Challenging)

Learners draw a diagram to show the main parts of a biosensor and annotate to show the principles of operation. (F)

Note

Online http://www.southernbiological.com/kits-and-equipment/specialised-laboratory-and-field-equipment/urine-testing/g10-41-diastix/ Textbooks/Publications Bio Factsheet 157: Diabetes – Management or Cure? Bio Factsheet 167: Biosensors Past Papers Paper 41, Nov 2011, Q2 (b)




http://www.southernbiological.com/kits-and-equipment/specialised-laboratory-and-field-equipment/urine-testing/g10-41-diastix/





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Link with previous work on insulin (14.1.h) and a practical for immobilised enzymes (3.2.d).

Note that some textbooks state that the oxidation of glucose produces, gluconolactone, which is an intermediate of gluconic acid.

Discuss ideas and developments in the commercial production of glucose biosensors, e.g. devices that can control and regulate insulin doses.

Learners should be able to use the principles of operation to apply to a design that they may not have come across.

14.1.l explain how urine analysis is used in diagnosis with reference to glucose, protein and ketones Key concepts Biochemical processes, Observation and experiment

Learners reflect back to14.1.f and explain why glucose and proteins would not normally be found in urine in detectable levels.

Explain that ketones are products of carbohydrate, protein and lipid metabolism, but high levels in urine may indicate ill health, such as in uncontrolled type I diabetes.

Explain that a urine analysis could indicate a condition: glycosuria and diabetes mellitus; proteinuria / albuminuria / microalbuminuria and renal disease or damage e.g. that may have been caused as a result of long-term type II diabetes. (W) (Basic) o Learners make outline notes on each of the three named urine

compounds. o Notes to include the diagnostic role of urine dipsticks (specific for each or

multiple combination strips testing for all three). (I) (Basic)

Note

Very low concentrations are excreted by healthy people, levels detected by urine dipsticks are indicative of possible health problems.

Details of other tests that can be performed on urine are not required.

Online http://www.patient.co.uk/doctor/urine-dipstick-analysis http://www.medicinenet.com/urine_tests_for_diabetes/article.htm Past Papers Paper 41, Nov 2011, Q2 (a)

15.1.l explain the roles of the hormones FSH, LH, oestrogen and progesterone in controlling changes in the ovary and uterus during the human menstrual cycle

Learners review the endocrine system and hormones with a short written test.

Discuss the different origins of the named hormones involved in the menstrual cycle, explaining target tissues differ. o Emphasise for later their importance in synchronising activities of the

ovary and uterus. (W) (Basic)

Use diagrams to describe the maturation of the follicle in the ovary, ovulation and the formation of the corpus luteum.

Online http://www.biologymad.com/master.html?http://www.biologymad.com/Hormones/Hormones.htm http://highered.mcgraw-hill.com/sites/0072495855/learner_view0/chapter28/animation__positive_

http://www.patient.co.uk/doctor/urine-dipstick-analysis

http://www.patient.co.uk/doctor/urine-dipstick-analysis

http://www.medicinenet.com/urine_tests_for_diabetes/article.htm

http://www.medicinenet.com/urine_tests_for_diabetes/article.htm

http://www.biologymad.com/master.html?http://www.biologymad.com/Hormones/Hormones.htm



http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__positive_and_negative_feedback__quiz_1_.html




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o Describe the events occurring in the uterus. (W) (Basic)

Learners draw a large outline graph. The x-axis being time (to 28 days – explain that cycles may be longer or shorter), y-axis being hormone concentration (arbitrary units). o Learners sketch diagrams of (i) the physical changes in the uterus over 28

days (above the graph), and (ii) the changes occurring in the ovary (below the graph). (I) (Basic)

o Using description and question and answers build up the graph to show the changing concentrations of the hormones over the 28 days (use a method to distinguish oestrogen and progesterone, the sex hormones, from FSH and LH, the two pituitary hormones.

o Discuss the feedback mechanisms that occur to enable the cycle to be controlled, learners annotate or add bullet point notes. (W) (I) (Challenging)

Extension: learners investigate the role of gonadotrophin releasing hormone (GnRH) in the control of the menstrual cycle. (I) (Challenging)

Learners discuss the changes to the graph(s) for shorter / longer cycles, explaining the reasons for their choices. (G) (Challenging)

Learners describe specific examples within the cycle of positive and negative feedback mechanisms. (I) (Challenging)

Learners complete unlabelled diagrams and graphs showing the events in the menstrual cycle. (F)

Note

It may be beneficial for learners to know the full names of FSH and LH: they are not required learning.

and_negative_feedback__quiz_1_.html http://highered.mcgraw-hill.com/sites/0072495855/learner_view0/chapter28/animation__maturation_of_the_follicle_and_oocyte.html Textbooks/Publications Bio Factsheet 57: Oestrous cycles. Includes the menstrual cycle Past Papers Paper 41, June 2012, Q5 (a) Paper 42, Nov 2013, Q4

15.1.m outline the biological basis of contraceptive pills containing oestrogen and/or progesterone Key concepts Observation and experiment

Learners research how the combined oral contraceptive pill prevents pregnancy and compare this with the progesterone /progestin-only pill. (H) (Basic)

Learners consider how concentrations of oestrogen and progesterone differ in women who are taking the contraceptive pill. o Learners explain the effects of these differences in terms of the feedback

mechanisms discussed in 15.1.l. (I) (Challenging)

Note

Online http://www.patient.co.uk/search.asp?searchTerm=contraceptive+pill&collections=Condition_Leaflets http://hcd2.bupa.co.uk/fact_sheets/html/hormonal_contraception.html Past Papers Paper 43, June 2011, Q3 (b)



http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__maturation_of_the_follicle_and_oocyte.html




http://www.patient.co.uk/search.asp?searchTerm=contraceptive+pill&collections=Condition_Leaflets



http://hcd2.bupa.co.uk/fact_sheets/html/hormonal_contraception.html

http://hcd2.bupa.co.uk/fact_sheets/html/hormonal_contraception.html


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The role of oestrogen and/or progesterone in controlling fertility is an extension of learners’ knowledge and understanding of the menstrual cycle.


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Unit 11: Plant physiology and biochemistry


As with respiration, learners should be familiar with the concept of energy transfer, for example from light energy to chemical energy. They should have a sound understanding of what a molecule is, and understand chemical formulae and equations. It would be helpful if they understood the concept of oxidation and reduction, at least at a simple level. Knowledge from AS Level of plant cell structure and of gene expression will help understanding of the role of gibberellin in cell elongation. It would be helpful if learners had an appreciation of the importance of communication, control and coordination in multicellular organisms. Context

This unit considers another aspect of the key concept of biological processes and studies the transfer of energy from light energy to the energy contained in organic compounds in living organisms. It has close links to Unit 9, Respiration, and revisits the concepts involved in the synthesis of ATP by chemiosmosis. It builds on material covered at AS Level: enzymes and biological molecules, especially glucose and starch, from Unit 1; plant cell structure and chloroplast structure and function from Unit 2; and leaf structure, including stomata from Unit 4. Having considered mammalian physiology in Unit 10, the plant hormones abscisic acid and gibberellin are used to exemplify communication, control and coordination in plants. Learners first come across gibberellin when studying selective breeding in Unit 7. This unit could be taught before Unit 9, Respiration, if it is felt more logical to introduce learners first to the process involved with the initial input of energy into the ecosystem. Outline

The unit begins with an overview of photosynthesis, highlighting the transfer of energy and the link between the light dependent and light independent stages. The light absorbing pigments are introduced and linked to the concepts involved with absorption and action spectra: learners can also separate photosynthetic pigments by chromatography. The light dependent and light independent stages of photosynthesis are described. The concept of limiting factors is introduced and learners have the opportunity of investigating factors affecting the rate of photosynthesis. A consideration of how this knowledge can be applied to crop plants is included. More detail is provided of the ways in which the structure of a chloroplast is suited to its functions. Learners also consider how some plants have evolved to cope with life in hot environments. Response to an external stimulus is exemplified by a study of the Venus fly trap. Stomatal closure and opening, including the role of abscisic acid, the role of auxin in cell elongation and the effect on gene activation of gibberellin is covered. There are numerous practical opportunities within this unit to develop skills relating to planning, data analysis and the evaluation of investigations. Teaching time



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13.1.b state the sites of the light dependent and the light independent stages in the chloroplast Key concepts Cells as the units of life, Biochemical processes

Project or show an image or diagram of a chloroplast and check learner knowledge from Unit 1 by a question and answer session. o Learners explain why the thylakoid membranes are the location of ATP

synthesis (refer back to mitochondrial membranes: site of ATP synthase, location for photosynthetic pigments).

o Learners suggest why the stroma is the site of the Calvin cycle (enzyme reactions). (W) (Challenging)

Note

A review may be necessary of the anatomy of the leaf, so that learners can visualise mesophyll tissue and mesophyll cells containing chloroplasts.

13.3.a may be taught first to give a visual overview of where the processes of photosynthesis occur.

Online http://resources.teachnet.ie/foneill/photo.html

13.1.c describe the role of chloroplast pigments (chlorophyll a, chlorophyll b, carotene and xanthophyll) in light absorption in the grana Key concepts Cells as the units of life

Allow learners to state the role of chlorophyll before raising the level of understanding to explain that the light energy needs to be transferred. Explain that: o Absorption occurs in areas of the thylakoid membrane that contain

photosystems. o Chlorophyll a and chlorophyll b are two types of chlorophyll molecule in a

typical photosystem, along with other photosynthetic pigments, e.g. carotenes and xanthophylls.

o Each type of pigment absorbs certain wavelengths of light and reflects others (mention the antenna complex).

o Absorbed energy is passed on to a special pair of chlorophyll molecules that can pass on energetic/excited electrons to electron acceptors. (W) (Challenging)

Learners label and annotate an unlabelled diagrammatic version of a photosystem as you talk them through the various components. o Learners note that: the special pair act as the reaction centre and the

others as accessory pigments; in Photosystem I (PI) the pair have a characteristic absorption wavelength of 700 nm (P700), and in PII of 680 nm (P680).

o Refer to the higher energy state of the electrons as photoactivation of chlorophyll. (I) (Challenging)

Online http://www.saps.org.uk/secondary/teaching-resources/283-photosynthesis-how-does-chlorophyll-absorb-light-energy http://phototroph.blogspot.ca/ Textbook/Publications Bio Factsheet 63: Pigments in plants

http://resources.teachnet.ie/foneill/photo.html

http://resources.teachnet.ie/foneill/photo.html

http://www.saps.org.uk/secondary/teaching-resources/283-photosynthesis-how-does-chlorophyll-absorb-light-energy




http://phototroph.blogspot.ca/


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Note

Explain that xanthophylls and carotenes are carotenoids.

This overlaps with 13.1.f so details of the photosystems may be taught there.

13.1.d interpret absorption and action spectra of chloroplast pigments Key concepts Cells as the units of life, Organisms in their environment, Observation and experiment

Background practical to help understanding: learners follow, or have demonstrated or described, a protocol to measure an absorption spectrum to see how the curve on the graph is obtained. o Explain that absorption is measured using a spectrophotometer). (W) (P)

(I)

Learners study separate absorption graphs for each of the chloroplast pigments (i.e. each has a characteristic absorption spectrum): check understanding with a worksheet. (I) (Basic)

Provide learners with a ‘classic’ absorption spectrum graph (includes the main pigments) and a set of questions assessing ability to extract data and show understanding. o Learners suggest the advantages to plants of having different pigments

(extends the range of light wavelengths absorbed). (F)

Explain how the graph for the action spectrum of photosynthesis is obtained. (W) (Basic)

Show learners a ‘classic’ action spectrum with peaks in the red and blue regions and sketch an absorption spectrum graph of pigment ‘X’ (actually chlorophyll a) and a separate one for a pigment ‘Y’ (peaking in the green region). o Learners suggest, with a reason, which is most likely to be involved in light

absorption for photosynthesis, so that the correlation between absorption and action spectra is seen. (W) (Basic)

Explain that there are more pigments involved than those usually shown, so the absorption spectrum graph is only similar to the action spectrum graph. o Explain that there are different carotenes and xanthophylls and different

plants have a characteristic set of pigments. (W) (Basic)

Note

Check that the absorption spectrum is well understood before moving onto the action spectrum, ensuring that learners make the association between the two.

Online http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ActionSpectrum.html Textbooks/Publication Siddiqui p.91 Past papers Paper 51, Nov 2011, Q1 (a)(b)

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ActionSpectrum.html




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PII PI


13.1.e use chromatography to separate and identify chloroplast pigments and carry out an investigation to compare the chloroplast pigments in different plants (reference should be made to Rf values in identification) Key concepts Observation and experiment

Practical: learners could carry out the separation for pigments of one plant, and compare results with others that have used different plants. o Learners make measurements and calculate Rf values, comparing with

published values to make identifications. (G) (I) (Basic)

Practical booklet 8 is a protocol for separating chloroplast pigments by paper chromatography. Colours fade relatively quickly so measurements should be made as soon as possible (or take photographs) after removing chromatograms from the solvent.

Practical booklet 8 Online http://www.saps.org.uk/secondary/teaching-resources/181-learner-sheet-10-thin-layer-chromatography-for-photosynthetic-pigments Textbook/Publications King p.113-114 Siddiqui p.90-91 Past Papers Paper 41, Nov 2011, Q10 (b)

Paper 51, Nov 2011, Q1 (c)(d)(e) Paper 53, Nov 2011, Q1 (d)(ii)

13.1.f describe the light dependent stage as the photoactivation of chlorophyll resulting in the photolysis of water and the transfer of energy to ATP and reduced NADP (cyclic and non-cyclic photophosphorylation should be described in outline only) Key concepts Biochemical processes

Use a diagram to ask learners questions about what happens in a photosystem (13.1.c). o Ensure learners know that excitation of energetic electrons results in a

transfer to an acceptor. o Explain that the absorption of light energy in PII also triggers the

photolysis of water by an enzyme (termed the oxygen evolving complex, closely located to the reaction centre). (W) (Basic)

With verbal prompts, learners build up the ‘Z-scheme’ to produce an outline of non-cyclic photophosphorylation and include explanations. o Sketch a ‘rising’ letter ‘N’, then add PII, then PI (represent

energy levels). o Add circles for the electron transport chain carriers (or label

ETC) and add arrows to show the electron pathway. o Add arrows to show the production of ATP as electrons flow down the

ETC. o Show the photolysis of water, with electrons replacing the gap in PII,

oxygen evolved. o Show the electrons accepted by NADP to produced reduced NADP. o Add the title non-cyclic photophosphorylation (noted for 13.1.a later). (I)

Online http://cnx.org/content/m48011/latest/ http://www.life.illinois.edu/govindjee/textzsch.htm http://www.johnkyrk.com/photosynthesis.html

Textbook/Publications Bio Factsheet 02: The essential guide to photosynthesis. Bio Factsheet 153: The Light Dependent Stage of Photosynthesis Past Papers Paper 43, Nov 2013, Q7 (a)

http://www.saps.org.uk/secondary/teaching-resources/181-learner-sheet-10-thin-layer-chromatography-for-photosynthetic-pigments




http://cnx.org/content/m48011/latest/

http://www.life.illinois.edu/govindjee/textzsch.htm

http://www.life.illinois.edu/govindjee/textzsch.htm

http://www.johnkyrk.com/photosynthesis.html

http://www.johnkyrk.com/photosynthesis.html


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(Basic)

Learners repeat the construction of the Z-scheme and add explanatory notes without help. (F) o Describe cyclic photophosphorylation. o Learners suggest why only ATP can be synthesised. o Learners add this in a different colour to their Z-scheme. (I) (Basic)

Learners revise work on chemiosmosis (Unit 9) to give an account of ATP synthesis at the thylakoid membrane. A partially labelled diagram showing a section through the thylakoid membrane with electron carriers of the ETC and the ATP synthase complex can be used as stimulus. (H) (Challenging)

12.1.e (ii) explain that the synthesis of ATP is associated with the electron transport chain on the membranes of mitochondria and chloroplasts (see 12.2.g) Key concepts Cells as the units of life, Biochemical processes

Only part of this learning objective is included here: explain that the synthesis of ATP is associated with the electron transport chain on the membranes of chloroplasts (see 12.2.g)

Learners complete a short written test to remind them of previous work o Chloroplasts are cellular structures where ATP is formed. o ATP is an energy transfer molecule. o The initial energy input for chloroplasts is light energy and for

mitochondria, energy-containing organic compounds. o The ETC involves thylakoid membrane proteins capable of accepting and

donating electrons. (F)

Online http://www.ncbi.nlm.nih.gov/books/NBK21063/ Textbook/Publications Bio Factsheet 153: The Light Dependent Stage of Photosynthesis Past papers Paper 41, June 2013, Q10 (b)

13.1.a explain that energy transferred as ATP and reduced NADP from the light dependent stage is used during the light independent stage (Calvin cycle) of photosynthesis to produce complex organic molecules Key concepts Biochemical processes, Organisms in their environment

In groups learners construct a large, poster-sized concept map / spider diagram with photosynthesis as a topic. (G) (Basic)

Discuss and agree as a class the main points and improve ideas to A Level standard. Learners then make notes in diagrammatic or bullet-point form. o An overall equation for photosynthesis (word equation changed to

chemical formulae, balanced). o Two main stages, occurring in the chloroplasts of mesophyll cells and both

involving enzymes. o In the light dependent stage, light energy is transferred to ATP and the

reduced coenzyme, NADP. o Oxygen (waste product) from this stage can be used for aerobic

respiration (in plant or released into the atmosphere to other organisms). o In the light independent stage (also termed the Calvin cycle), carbon

Online http://www.saps.org.uk/secondary/teaching-resources/134-photosynthesis-a-survival-guide-teaching-resources http://photoscience.la.asu.edu/photosyn/study.html http://www.johnkyrk.com/photosynthesisdark.html http://www.biologymad.com/master.html?http://www.biologymad.com/a2biology.htm http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Plants/01-



http://www.saps.org.uk/secondary/teaching-resources/134-photosynthesis-a-survival-guide-teaching-resources




http://photoscience.la.asu.edu/photosyn/study.html

http://photoscience.la.asu.edu/photosyn/study.html

http://www.johnkyrk.com/photosynthesisdark.html

http://www.johnkyrk.com/photosynthesisdark.html

http://www.biologymad.com/master.html?http://www.biologymad.com/a2biology.htm



http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Plants/01-Photosynthesis.htm



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dioxide, ATP and NADPH are used for the production of complex organic molecules, such as glucose and starch. (W) (I) (Challenging)

Note

Learners should understand the terms ‘autotroph’, ‘photoautotroph’ and ‘producer’.

Avoid using the terms ‘light reaction’ and ‘dark reaction’.

Photosynthesis.htm Past papers Paper 43, Nov 2013, Q7 (b)

13.1.g outline the three main stages of the Calvin cycle:

fixation of carbon dioxide by combination with ribulose bisphosphate (RuBP), a 5C compound, to yield two molecules of GP (PGA), a 3C compound

the reduction of GP to triose phosphate (TP) involving ATP and reduced NADP

the regeneration of ribulose bisphosphate (RuBP) using ATP

Key concepts Biochemical processes

Discuss why the light dependent stage of photosynthesis needs to occur when no glucose has yet been made (allows the transfer of light energy to ATP and reduced NADP). o Learners write out the overall equation of photosynthesis to spot that

carbon dioxide has not yet been involved (sets the scene for the Calvin cycle). (W) (Basic)

Learners link together a set of statements, based around the ideas in the learning objectives and including rubisco, to describe the Calvin cycle. o Provide curved arrows, so that they can create a cycle with their

statements. (P) (I) (Challenging)

Discuss their cycles. o Emphasise the roles of reduced NADP and ATP (include the concept of

recycling to the light dependent stage). o Explain that the steps are catalysed by enzymes. o Show how 6 carbon dioxide molecules are required to produce 1 glucose

molecule, so that the overall equation for photosynthesis makes sense. o Learners then produce their own annotated Calvin cycle. (W) (I)

(Challenging)

Background: learners investigate the experiments carried out by Calvin and his colleagues using the ‘lollipop’ apparatus. (I) (Challenging)

Learners annotate fully a skeleton outline of the Calvin cycle (provide a variety so that each contains different information – could be differentiated). (F) (Basic) (Challenging)

Note

For ‘error-free learning’, use only the syllabus names and abbreviations: o GP (glycerate 3-phosphate) or PGA (3PG / 3-phosphoglycerate /

3-phosphoglyceric acid)

Online http://www.science.smith.edu/departments/Biology/Bio231/calvin.html http://www.wiley.com/college/boyer/0470003790/animations/photosynthesis/photosynthesis.htm http://nobelprize.org/nobel_prizes/chemistry/laureates/1961/calvin-lecture.pdf Textbooks/Publications Bio Factsheet 02: The essential guide to photosynthesis. Bio Factsheet 227: RuBP carboxylase – the most important enzyme on the planet? Past Papers Paper 41, June 2011, Q10 (b) Paper 43, June 2011, Q10 (b)


http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

http://www.wiley.com/college/boyer/0470003790/animations/photosynthesis/photosynthesis.htm



http://nobelprize.org/nobel_prizes/chemistry/laureates/1961/calvin-lecture.pdf




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o TP (triose phosphate). Avoid other common names: glyceraldehyde 3-phosphate (GALP); 3-phosphoglyceraldehyde (PGAL)

o Explain that other acceptable names are used.

No names of enzymes, other than rubisco, are required.

13.1.h describe, in outline, the conversion of Calvin cycle intermediates to carbohydrates, lipids and amino acids and their uses in the plant cell Key concepts Biochemical processes

Agree that GP is the raw material for producing carbohydrates, lipids and amino acids (no details of pathways required). o Learners add this information to their Calvin cycle. (I) (Basic)

Briefly discuss how two molecules of GP can produce a hexose sugar. (W) (Basic)

Discuss, using question and answer, the use of hexose sugars (glucose and fructose, Unit 1), including: o Immediate use to release energy as respiratory substrates. o Synthesis of sucrose for transport to sinks (revise plant transport, Unit 4). o Conversion to starch or lipid for energy storage. o Production of structural compounds (cellulose). o Learners suggest what else is required to synthesise amino acids for

proteins (uptake of nitrate and sulfate ions in the roots). (W) (Basic)

Learners produce an outline set of notes from the discussion. (I) (Basic)

13.3.a describe the relationship between structure and function in the chloroplast using diagrams and electron micrographs Key concepts Cells as the units of life, Biochemical processes

Place the chloroplast into context as a summary. o Learners identify: the photosynthetic organism (plant); the organ of

photosynthesis (leaf); the main photosynthetic tissue (palisade mesophyll); the organelle of photosynthesis (chloroplast); the structures of the chloroplast. (W) (Basic)

Learners draw a labelled diagram of a chloroplast, annotating (or write a summary) to show how the chloroplast is adapted for photosynthesis. o Note the requirement for membranes and intermembrane spaces to

generate ATP as electrons pass along a chain of electron carriers. o Note the locations of the light dependent stage and the light independent

stage. (I) (Challenging)

Learners interpret photomicrographs and electron micrographs of chloroplasts, drawing labelled diagrams. (I) (Basic)

Online http://www.vcbio.science.ru.nl/en/image-gallery/show/PL0130/ http://www.vcbio.science.ru.nl/en/fesem/applets/chloroplast/ http://faculty.uca.edu/johnc/Chloroplast_and_microbodies.jpg Textbook/Publications Bio Factsheet 198: Chloroplasts – structure and function Bio Factsheet 61: Chloroplasts and mitochondria Past Papers

http://www.vcbio.science.ru.nl/en/image-gallery/show/PL0130/

http://www.vcbio.science.ru.nl/en/image-gallery/show/PL0130/

http://www.vcbio.science.ru.nl/en/fesem/applets/chloroplast/

http://www.vcbio.science.ru.nl/en/fesem/applets/chloroplast/

http://faculty.uca.edu/johnc/Chloroplast_and_microbodies.jpg

http://faculty.uca.edu/johnc/Chloroplast_and_microbodies.jpg


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Paper 41, Nov 2011, Q10 (a)

13.2.a explain the term limiting factor in relation to photosynthesis Key concepts Biochemical processes, Organisms in their environment

Show learners a number of definitions of the term limiting factor. As a group produce an explanation to note down that is in the context of photosynthesis. (W) (I) (Basic)

Learners draw a generalised graph showing the rate of photosynthesis on the y-axis and the factor on the x-axis. o Label the graph with the regions where the factor directly affects the rate

of photosynthesis and those where other factors become limiting. (I) (Basic)

13.2.b explain the effects of changes in light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis Key concepts Biochemical processes, Organisms in their environment, Observation and experiment

Learners suggest the factors that may affect the rate of photosynthesis, and discuss ways in which the rate could be measured. (W) (Basic)

Learners suggest the parts of the photosynthetic process that involve enzymes, and hence affect photosynthetic rate. o Light dependent stage: photolysis of water; synthesis of ATP (ATP

synthase); transfer of electrons to NADP for reduction. o Light independent stage: each of the steps of the Calvin cycle (the bulk of

enzyme-catalysed reactions occur here).

Learners use their notes on chloroplast pigments and the two stages of photosynthesis to suggest how changes in carbon dioxide concentration and light intensity will affect the rate of photosynthesis. o Include an explanation as to why the light independent stage will not

operate when there is no light. (I) (Basic) (Challenging)

To link back to 13.2.a learners interpret graphs showing the effects of limiting factors, explaining why the rate of photosynthesis changes and using extracted date to support their answer. (I) (Challenging)

Online http://www.biology4all.com/resources_library/details.asp?ResourceID=43 http://resources.teachnet.ie/foneill/exper.htm http://www.assessnet.org.uk/e-learning/ Textbook/Publications King p.115-117, 149 Siddiqui p.86-89, 94 Bio Factsheet 136: Practical Investigations for Photosynthesis Bio Factsheet 25: Tackling data interpretation questions II: photosynthesis (limiting factors) Past Papers Paper 41, June 2012, Q8 (a)(b)

13.2.c explain how an understanding of limiting factors is used to increase crop yields in protected environments, such as glasshouses

Explain that knowledge of limiting factors can be used to control the growing conditions of commercial crops, especially in protected environments. (W) (Basic)

Brainstorm ideas as to what growers can do to increase crop yields in glasshouses. Include:

Online http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/photosynthesis/photosynthesisrev3.shtml http://www.omafra.gov.on.ca/english/



http://resources.teachnet.ie/foneill/exper.htm

http://resources.teachnet.ie/foneill/exper.htm

http://www.assessnet.org.uk/e-learning/

http://www.assessnet.org.uk/e-learning/

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/photosynthesis/photosynthesisrev3.shtml



http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm


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o Artificial light (photosynthesis for more hours of the day; increase light intensity on days with little sunlight).

o Use of paraffin lamps (carbon dioxide and heat). (W) (Basic) o Learners make notes and explain how these will improve yield. (F)

crops/facts/00-077.htm

13.2.d carry out an investigation to determine the effect of light intensity or light wavelength on the rate of photosynthesis using a redox indicator (e.g. DCPIP) and a suspension of chloroplasts (the Hill reaction) Key concepts Biochemical processes, Observation and experiment

From 13.2.b learners will know that the production of oxygen can be used to measure the rate of photosynthesis. o Learners suggest why the rate of production of NADP in the light

dependent stage correlates with the rate of photosynthesis. o Explain that a way of measuring this could be to use a different electron

acceptor, DCPIP, which can be visualised (blue dye that becomes colourless when reduced). (W) (Basic)

o Learners suggest how DCPIP can be used to measure rate. (W) (Challenging)

Learners carry out a version of the Hill reaction practical or watch it demonstrated and then explain a set of results. Ensure that both investigations, light intensity and light wavelength, are covered. (P) (I) (H) (Challenging)

Discuss the findings of the original investigation performed by Robin Hill: oxygen is evolved in the absence of carbon dioxide; the electrons transferred to the electron acceptor originate from water. (W) (Challenging)

Practical booklet 9 (Hill reaction) uses melting point tubes as reaction vessels and does not use a centrifuge. Learners can investigate the effect of both light wavelength and light intensity on the rate of photosynthesis. Pooled data for analysis may be collected as preparation for Paper 5. Learners can also use the technique to devise plans that can be peer reviewed (see 12.2.h and 12.2.m).

Practical booklet 9 Online http://www.nuffieldfoundation.org/practical-biology/investigating-light-dependent-reaction-photosynthesis http://www.saps.org.uk/secondary/teaching-resources/157-measuring-the-rate-of-photosynthesis Textbook/Publications Siddiqui p.93-93 Past paper Paper 53, Nov 2011, Q1 (a)(b)(c)

13.2.e carry out investigations on the effects of light intensity, carbon dioxide and temperature on the rate of photosynthesis using whole plants, e.g. aquatic plants such as Elodea and Cabomba

Practical: learners investigate the effect of light intensity, light wavelength, carbon dioxide concentration and temperature on the rate of photosynthesis. o Learners design and carry out at least one investigation of their own, once

a technique has been shown to them. (I) (Challenging) o Learners explain how the plan can be modified to investigate the effect of

limiting factors. (I) (Challenging)

Note

Online http://www.saps.org.uk/secondary/teaching-resources/190-using-pondweed-to-experiment-with-photosynthesis- http://www.saps.org.uk/secondary/teaching-resources/284-investigating-photosynthesis-with-leaf-discs

http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm

http://www.nuffieldfoundation.org/practical-biology/investigating-light-dependent-reaction-photosynthesis



http://www.saps.org.uk/secondary/teaching-resources/157-measuring-the-rate-of-photosynthesis



http://www.saps.org.uk/secondary/teaching-resources/190-using-pondweed-to-experiment-with-photosynthesis-




http://www.saps.org.uk/secondary/teaching-resources/284-investigating-photosynthesis-with-leaf-discs




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Key concepts Observation and experiment

Carbon dioxide concentration can be varied by using an aquatic (water) plant in varying concentrations of solutions containing sodium hydrogen carbonate (sodium bicarbonate).

http://www.saps.org.uk/secondary/teaching-resources/285-learner-sheet-20-starch-production-in-plants-during-photosynthesis

13.3.b explain how the anatomy and physiology of the leaves of C4 plants, such as maize or sorghum, are adapted for high rates of carbon fixation at high temperatures in terms of:

the spatial separation of initial carbon fixation from the light dependent stage (biochemical details of the C4 pathway are required in outline only)

the high optimum temperatures of the enzymes involved

Key concepts Biochemical processes, Natural selection, Organisms in their environment

Learners review C3 photosynthesis by completing worksheets with gaps or by rearranging cards describing stages and then suggest why the term C3 plant is used. (W) (P) (I) (F) (Basic)

Explain that rubisco can also catalyse the oxygenation of RuBP. o Use diagrams, and remind learners of enzyme inhibition (AS Level) to

prompt them to suggest why the reaction is favoured in high oxygen concentrations.

o Learners suggest the conditions when oxygen concentrations will be high (high light intensity and high temperatures increase rate of light dependent stage). (W) (Basic)

o Learners write an explanation of photorespiration. (I) (Basic) (Challenging)

Explain that C4 plants are traditionally from hotter environments. (W) (Basic)

Describe, using diagrams, the structural and functional features of maize or sorghum as examples of C4 plants. (W) (Challenging) o Learners suggest how the features adapt the plants to reduce the effects

of photorespiration and allow high rates of carbon fixation. o Learners label and annotate a diagram of a section through the leaf of a

C4 plant. o Learners produce a comparison table of C3 (see 13.3.a) and C4 leaf

structure. (W) (I) (Challenging)

Discuss the effect of higher temperatures on C3 enzymes versus C4 enzymes. (W) (Basic) o Learners use their graph(s) from 13.2.b (temperature v rate of

photosynthesis), to sketch in a curve for a C4 plant. (I) (Basic)

Extension: learners consider the effects of global warming on the distribution of C4 plants. (I) (Challenging)

Online http://www.icrisat.org/crop-sorghum.htm http://en.wikipedia.org/wiki/Sorghum http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html http://www.marietta.edu/~biol/biomes/photosynthesis.htm www.biologymad.com/resources/Crop%20Plants.pps Past Papers Paper 43, June 2011, Q4

15.2.a describe the rapid response of the

Display photographs of the Venus fly trap plant and its modified leaves. o Leaners brainstorm uses of nitrogen in plants.

Online http://plantsinmotion.bio.indiana.edu/

http://www.saps.org.uk/secondary/teaching-resources/285-student-sheet-20-starch-production-in-plants-during-photosynthesis




http://www.icrisat.org/crop-sorghum.htm

http://www.icrisat.org/crop-sorghum.htm

http://en.wikipedia.org/wiki/Sorghum

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html

http://www.marietta.edu/~biol/biomes/photosynthesis.htm

http://www.marietta.edu/~biol/biomes/photosynthesis.htm



http://plantsinmotion.bio.indiana.edu/plantmotion/movements/nastic/nastic.html


V3.1 180


Venus fly trap to stimulation of hairs on the lobes of modified leaves and explain how the closure of the trap is achieved Key concepts Cells as the units of life, Organisms in their environment

o Discuss the need for a source of nitrogen in addition to the products of photosynthesis.

o Explain that the plant requires supplemental nitrogen owing to low levels of nitrogen in the bog habitats where it is found. (W) (Basic)

Explain to learners that the equivalent of an action potential occurs to cause the snapping shut of the trap to catch insects. o Briefly review learner understanding of stimulus, receptor and action

potential (Unit 10). (W) (Basic)

Learners sequence a set of statements as the basis to make notes. Ideas to include: o Stimulus = insect movement (mechanical). o Receptors = hair cells (upper leaf surface). o Touching two times in succession, i.e. the presence of an insect, results in

depolarisation of the hair cell membrane (owing to an influx of positive ions).

o If the depolarisation is large enough, action potentials spread across from receptor cells to reach cells on the outside surface.

o One possible mechanism of closure of the trap: H

+ is pumped out of cells on the outside surface into the cell walls

The low pH causes cell wall loosening and movement out of H+ leads

to influx of Ca2+

Water follows osmotically and the cells swell to snap the trap shut. (I)

(Challenging)

Background: learners investigate how carnivorous plants like the Venus flytrap digest and absorb their insect catch. (I) (Basic)

plantmotion/movements/nastic/nastic.html http://www.botany.org/Carnivorous_Plants/venus_flytrap.php



http://www.botany.org/Carnivorous_Plants/venus_flytrap.php

http://www.botany.org/Carnivorous_Plants/venus_flytrap.php


V3.1 181


14.2.a explain that stomata have daily rhythms of opening and closing and also respond to changes in environmental conditions to allow diffusion of carbon dioxide and regulate water loss by transpiration Key concepts Cells as the units of life, Organisms in their environment

Learners link stomatal opening and closure to transpiration (Unit 4) and photosynthesis. o Discuss the environmental stimuli for opening and closure (learners recall

factors affecting transpiration rate). o Explain the ‘internal clock’ of guard cells and the daily rhythm of opening

during the day and closing during the night. (W) (Basic)

Provide graphs showing daily rhythms of opening and closing, with the effects of changing environmental conditions on particular days. o Learners describe and explain the graph, using this as the basis of their

notes. (I) (Challenging)

Note

Mention the term circadian rhythm (not required learning).

Very high wind speeds may also cause stomatal closure – some books do not show this on typical graphs.

Online http://www.tiem.utk.edu/~gross/bioed/webmodules/circadianrhythm.html

14.2.b describe the structure and function of guard cells and explain the mechanism by which they open and close stomata Key concepts Cells as the units of life, Biochemical processes

Learners draw and label a diagram of guard cells, making a note of their function. (I) (Basic)

Learners use an outline diagram of the events occurring for stomatal opening and complete a worksheet to describe and explain the mechanism involved (uses much knowledge from AS Level). (I) (Challenging)

Learners use knowledge of the mechanism of stomatal opening to write out and explain the sequence of events occurring for stomatal closure. (F)

Learners use prepared slides (see 7.2.e, Unit 4) to observe guard cells and stomata. (I) (Basic)

Learners observe stomatal opening and closure in temporary slides made of epidermal strips in solutions of different water potential. (I) (Basic)

Online http://www.phschool.com/science/biology_place/labbench/lab9/stomamov.html http://www.saps.org.uk/secondary/teaching-resources/104-stomata-function-guard-cells-and-transpiration

14.2.c describe the role of abscisic acid in the closure of stomata during times of water stress (the role of calcium ions as a second messenger should be emphasised) Key concepts

Describe the role of abscisic acid (ABA) as a 'stress hormone' to help plants survive difficult environmental conditions such as drought. (W) (Basic)

Explain to learners that calcium ions are important in plant cell signalling. (W) (Basic)

Learners make summary bullet-point notes based on the following ideas: o Guard cells have receptors for ABA: the presence of ABA results in high

concentrations of calcium ions within the cytoplasm. o ABA can inhibit the proton pump used to pump out protons, preventing the

Online http://labs.biology.ucsd.edu/schroeder/clickablegc.html#figure1 http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ABA.html http://www.plant-hormones.info/abscisicacid.htm

http://www.tiem.utk.edu/~gross/bioed/webmodules/circadianrhythm.html

http://www.tiem.utk.edu/~gross/bioed/webmodules/circadianrhythm.html

http://www.phschool.com/science/biology_place/labbench/lab9/stomamov.html



http://www.saps.org.uk/secondary/teaching-resources/104-stomata-function-guard-cells-and-transpiration



http://labs.biology.ucsd.edu/schroeder/clickablegc.html#figure1

http://labs.biology.ucsd.edu/schroeder/clickablegc.html#figure1

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ABA.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ABA.html

http://www.plant-hormones.info/abscisicacid.htm

http://www.plant-hormones.info/abscisicacid.htm


V3.1 182


Biochemical processes, Organisms in their environment

inward flux of potassium ions. o The presence of both ABA and calcium ions leads to changes in the

membrane that causes the opening of potassium ion channels. o The calcium ions, therefore, can be considered as a second messenger. o Movement out of potassium ions from the cell will cause stomatal closure

(see 14.2.b). (I) (Challenging)

Note

Not all the details of ABA and calcium ion involvement in stomatal closure are known: it is worth checking for updates.

The changes in the membrane are depolarisation as a result of activation of anion channels in the membrane (details not required).

As abscisic acid can enter cells, receptors could be membrane-bound or internally located.

Textbooks/Publications Bio Factsheet 48: Tackling exam questions: plant growth substances Bio Factsheet 111: Plant Growth Substances Past Papers Paper 43, June 2011, Q11 (a)

15.2.b explain the role of auxin in elongation growth by stimulating proton pumping to acidify cell walls Key concepts Cells as the units of life, Biochemical processes

Discuss how cell division and cell elongation will lead to plant growth and stem elongation. o Explain that auxin is a plant hormone involved in cell elongation. (W)

(Basic)

Discuss details of cell wall structure before outlining the sequence of events that occur (learners recall AS Level knowledge). Learners make notes to include: o Auxin increases the activity of proton pumps (ATP required) and protons

are pumped out of the cell into the cell wall. o The decrease in pH activates expansins (proteins) involved in loosening

cell wall structure. o Water moves in by osmosis, increasing turgor and allowing cells to

elongate. (W) (I) (Challenging)

Note

Auxins are a class of hormones, rather than one particular plant hormone. At this level the use of ‘auxin’ is acceptable. The same applies to gibberellins.

Online http://croptechnology.unl.edu/pages/informationmodule.php?idinformationmodule=998688536&topicorder=6&maxto=11&minto=1 http://home.earthlink.net/~dayvdanls/plant_grow.htm http://www.personal.psu.edu/fsl/ExpCentral/

15.2.c describe the role of gibberellin in the germination of wheat or barley

Introduce gibberellin as a hormone that promotes germination by breaking seed dormancy. o Agree what is meant by ‘germination’. (W) (Basic)

Practical booklet 10 Online

http://croptechnology.unl.edu/pages/informationmodule.php?idinformationmodule=998688536&topicorder=6&maxto=11&minto=1




http://home.earthlink.net/~dayvdanls/plant_grow.htm

http://home.earthlink.net/~dayvdanls/plant_grow.htm

http://www.personal.psu.edu/fsl/ExpCentral/

http://www.personal.psu.edu/fsl/ExpCentral/


V3.1 183



Learners annotate a diagram of a section through a wheat or barley grain, showing the sequential events occurring once water is imbibed. Use questioning and include: o Diffusion, e.g. of gibberellin from embryo to aleurone layer; o Transcription and translation (in aleurone layer cells for production of

digestive hormones); o Hydrolysis of starch and protein (by digestive enzymes) and use of

products for respiration and growth of seedling. (I) (Challenging)

Learners organise a set of statements to show the correct sequence of events in seed germination. (F)

Practical booklet 10: learners carry out practical to investigate the effect of different concentrations of gibberellic acid on stimulating amylase activity in germinating seeds. o The results can be analysed using the t-test (see 17.1.c). (P) (I) (Basic)

http://www.indiana.edu/~oso/animations/barley.html Textbooks/Publications King p.240-241 Past Papers Paper 43, June 2011, Q11 (b) Paper 41, Nov 2013, Q9

15.2.d explain the role of gibberellin in stem elongation including the role of the dominant allele, Le, that codes for a functioning enzyme in the gibberellin synthesis pathway, and the recessive allele, le, that codes for a non-functional enzyme Key concepts Cells as the units of life, DNA, the molecule of heredity

Remind learners of 15.2.b and explain that in stem elongation, gibberellin causes both cell division and cell elongation. (I) (Basic)

Learners recall basic points: the definition of an allele (Unit 3); genes code for polypeptides / proteins; enzymes are proteins; the definitions of dominant and recessive (alleles). (W) (Basic)

Explain that there is a gene responsible for expressing an enzyme that is important in the synthesis of active gibberellin. o State that there is a dominant allele for the functioning enzyme and a

recessive allele for a non-functioning enzyme. (W) (Basic)

Learners use knowledge of genetics and of the role of gibberellin to explain how plants that are LeLe and Lele will have tall stems, whereas plants that are lele will have short stems. (F)

Learners carry out practical work to investigate the effect of gibberellic acid on stem (hypocotyl) elongation and on seed germination (barley) (see 15.2.c).

Note

This could be amalgamated with 16.3.d.

Online http://www.tutorvista.com/content/biology/biology-iv/plant-growth-movements/gibberellins.php http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/Gibberellins.html http://www.plant-hormones.info/ Textbooks/Publications King p.244 Bio Factsheet 118: Germination Bio Factsheet 133: Comparing Chemical Communication in Plants and Animals Past Papers Paper 43, Nov 2012, Q10 (b)

16.3.d explain how gibberellin activates genes by causing the breakdown of

Explain that DELLA proteins are regulators of growth: they bind to transcription factors necessary for expression of genes coding for growth proteins.

Practical booklet 10 Online

http://www.indiana.edu/~oso/animations/barley.html

http://www.indiana.edu/~oso/animations/barley.html

http://www.tutorvista.com/content/biology/biology-iv/plant-growth-movements/gibberellins.php



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/Gibberellins.html


http://www.plant-hormones.info/


V3.1 184


DELLA protein repressors, which normally inhibit factors that promote transcription Key concepts Biochemical processes, DNA, the molecule of heredity, Observation and experiment

o Learners explain how the DELLA proteins can be considered repressors. (W) (Basic)

Explain that gibberellin can bind to intracellular receptor proteins (GID1) and that this leads to a complex with DELLA proteins, making them susceptible to degradation by the cell. o Learners suggest the consequences of this breakdown. (W)

(Challenging)

Learners describe the sequence of events that lead to an event such as stem elongation in the presence of gibberellins. (I) (Challenging)

Note

Learners could be directed to use this information on the mode of action of gibberellins in their interpretations of results from practical booklet 10 (see 15.2.c).




© Cambridge International Examinations 2014 Version 3.1 Updated: 16.02.16 Cambridge International Examinations 1 Hills Road, Cambridge, CB1 2EU, United Kingdom tel: +44 1223 553554 fax: +44 1223 553558 email: [email protected] www.cie.org.uk

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