Course Guide AS A2 OCR Biology - Pearson Education · PDF fileOCR Biology Course Guide ... OCR...

Pete KennedyFrank SochackiSue Hocking Mark WinterbottomSeries Editor: Sue Hocking

Exclusively endorsed by OCR for GCE Biology

In Exclusive Partnership

A2

Pete Kennedy and Frank SochackiSeries Editor: Sue Hocking

AS




OCR

Biology

Course GuideAS A2

Heinemann is working exclusively with OCR to produce an exciting suite of resources tailored to the new OCR GCE Biology specification. Written by experienced examiners, OCR AS and A2 Biology provide you with tailored support for teaching the revised specification. Comprehensive support for AS and A2, and motivating exam preparation in our unique Exam Café, will give your students every chance of success.

Exciting resources developed in exclusive partnership to support the new GCE Biology specification

Course Structure

AS

AS Student Book with Exam Café

CD-ROM


AS



AS Teacher Support CD-ROM

22

AS Revision Guide

Richard Fosbery and Ianto StevensSeries editor: Sue Hocking

AS




This revision guide is tailored to the OCR specification and exclusively endorsed by OCR for GCE Biology. It is written by experienced examiners and teachers, giving you:

complete coverage of the specification for the exams content organised by module and unit to follow the structure of the

specification and exams bite-sized chunks of information to make it easier to organise your

revision time quick-check revision questions so that you can test your own

knowledge easily hints and tips from examiners to help you avoid common errors lots of practice exam-style questions for each unit all the answers to questions so that you can check that you’re on the

right track.

Titles in this series:OCR AS Biology student book and exam café CD-ROM 978 0 435691 80 6OCR A2 Biology student book and exam café CD-ROM 978 0 435691 90 5OCR AS Biology Teacher Support CD-ROM 978 0 435691 77 6OCR A2 Biology Teacher Support CD-ROM 978 0 435691 91 2OCR AS Biology revision guide 978 0 435583 70 5OCR A2 Biology revision guide 978 0 435583 73 6

AS

Second Edition

01865 888118www.heinemann.co.uk


I S B N 978-0-435583-70-5

9 7 8 0 4 3 5 5 8 3 7 0 5

AS

01865 888118


ISBN 978 0 435961 77 6

Mike WinterbottomJenny Wakefi eld-Warren and Frank SochackiSeries Editor: Sue Hocking

Teacher SupportExclusively endorsed by OCR for GCE Biology A

Series Editor: Sue Hocking

A2

A2 Student Book with Exam Café

CD-ROM




A2

A2 Teacher Support CD-ROM

AS Revision Guide

A2

Exclusively endorsed by OCR for GCE Biology A

01865 888118Mike WinterbottomJenny Wakefi eld-Warren and Frank SochackiSeries Editor: Sue Hocking


ISBN 978 0 435961 91 2

Teacher Resource CD

Winterbottom • Wakefi eld-Warren • Frank SochackiSeries Editor: Sue Hocking

l OCR and Heinemann working in exclusive partnership to provide better support for you.

l Engaging resources written by experienced examiners and tailored to the new specification.

l A full ready-to-use teaching scheme that can be customised to give you total freedom and flexibility.

l Innovative Exam Café CD-ROM provided FREE in the back of every Student Book.

What you can expect from Heinemann’s OCR AS and A2 Biology

3

Student Book

Peter Kennedy

Frank SochackiHelen Eccles

Sue Hocking

Peter Kennedy

Frank Sochacki

Mark Winterbottom

Exam Café CD-ROM

Frank Sochacki

Jenny Wakefield-Warren

Robert Duncan

Robert Duncan

Frank Sochacki

Karen Stephens


Teacher Support CD-ROM

Frank Sochacki


Mark Winterbottom

Frank SochackiJenny Wakefield-Warren

Mark Winterbottom

Revision Guide

Richard FosberyIanto StevensJennifer Gregory

Richard FosberyIanto StevensJennifer Gregory

Authors

Our authors have been specially selected because of their expertise and experience as examiners and practising teachers, and are dedicated to providing you with a set of resources that meet your needs in the classroom.

AS

A2

Series EditorSue Hocking

82

83

Exercise/diet/smoking

Health aspects oflifestyle

Lungs

Exchange withcells

Tissue fluid

Blood vessels

Heart

Animals

Animals

Transpiration

Translocation

Leaves

Roots

Plants

Diffusion throughoutcell

Surface of body usedfor exchange

Exchange andtransport links

Digestivesystem

Low demand foroxygen and nutrients

Large surface-area-to-volume ratio

Single-celled organismsand small multicellular

organisms

Xylem

Plants

Phloem

Need fortransport

system

Need forspecial

exchangesurface

High demand foroxygen and nutrients

Small surface-area-to-volume ratio

Large multicellularorganisms

Living things

1.2 Exchange and transport summary

1 (a) State the names of the tissues labelled A–D below. [4]A

B

C

D

Figure 1

(b) Name the organ represented by Figure 1. [1]

2 (a) State the name of the type of muscle found in theheart.[1] (b) Explain why the muscle surrounding the left ventricle isthicker than that surrounding the right ventricle. [2] (c) Name the blood vessels that: (i) carry blood away from the ventricles; (ii) carry blood back towards the heart. [2]

3 (a) State two features of a good gaseous exchangesystem.[2] (b) Describe the route taken by air as it is inhaled. [3] (c) Name the air sacs in the lungs. [1]

4 (a) What immediate effect does exercise have on the heartrate?[1] (b) What happens to the tidal volume of the lungs duringexercise?[1] (c) Name two other exchange surfaces. [2]

5 Complete the following paragraph by filling in the blankspaces.Blood is .................................... in the lungs. The redpigment .................................. has a high affinity foroxygen. The pumping action of the ..........................creates pressure which pushes the blood around the body.In the tissues the partial pressure of ..................................is low. This causes the ................................ of theoxyhaemoglobin. In the tissues, the oxygen is used in theprocess of ................................. . Most of the carbondioxide produced in this process enters the.............................................. cells. Here it is converted to carbonic acidby the action of the enzyme carbonic anhydrase. Thecarbon dioxide is transported as .....................................back to the lungs.

[8]

6 (a) Explain the role of elastic tissue in the alveoli. [2] (b) Name the two types of cell found in the epithelium ofthe airways.[2] (c) Describe the action of the cilia in bronchi. [2]

7 (a) In a plant, name two tissues that may act as a source.[2] (b) Name the tissue that is used to transport sugars in aplant.[1]

8 (a) Explain why a large organism with a lowsurface-area-to-volume ratio needs a special surfacefor gaseous exchange.[3] (b) Explain how a higher concentration of carbon dioxidein the blood can cause extra oxygen to dissociate fromoxyhaemoglobin.[4]

9 (a) Describe how sucrose is loaded into the sieve tubeelement.[4] (b) Explain, using the term water vapour potential gradient,why increasing the wind speed will increase the rate oftranspiration.[3]

10 (a) Explain the importance of the Purkyne tissue incoordination of the cardiac cycle. [3] (b) Describe and explain the role of the coronary arteries.[3]

Practice questionsModule 2

Exchange and transportPractice questions

936 biology.U1 M2.indd 82-83

10/3/08 11:40:13 am

Student Books

8

9

1.1 3 Electron microscopes and cell details

Module 1Cells

Electron microscopes and cell details

By the end of this spread, you should be able to . . .

State the magni� cation that can be achieved with the electron microscope.

Explain the need for staining samples for use in light microscopy and electron microscopy.

The use of electronsLight microscopes have low resolution. This means that if the magnifi cation is above

×1500, the image isn’t clear. The wavelength of visible light ranges from about 400 to

750nm, so structures closer together than 200nm (0.2 m) will appear as one object.

We can achieve higher resolution with electron microscopes.

• Electron microscopes generate a beam of electrons.

• A beam of electrons has a wavelength of 0.004nm, 100000 times shorter than a light

wavelength.

• Electron microscopes can distinguish between objects 0.2nm apart.

• These microscopes use magnets (instead of lenses) to focus the beam of electrons

onto a prepared specimen.

• Electrons are not visible to the human eye. The image produced from the

electron beam is projected onto a screen or onto photographic paper to make a

black-and-white image (sometimes referred to as a ‘greyscale’ image).

• Such images are called electron micrographs.

• The resolution of an electron microscope is about 500000 times greater than that of

the human eye.

Two types of electron microscope

Transmission electron microscope (TEM)

• The electron beam passes through a very thin prepared sample.

• Electrons pass through the denser parts of the sample less easily, so giving some

contrast.

• The fi nal image produced is two-dimensional.

• The magnifi cation possible with a TEM is ×500000.

Scanning electron microscope (SEM)

• The electron beam is directed onto a sample. The electrons don’t pass

through the specimen.

• They are ‘bounced off’ (refl ected off) the sample.

• The fi nal image produced is a 3D view of the surface of the sample.

• The magnifi cation possible with an SEM is about ×100000.

Advantages and limitations of the electron microscope

• The resolution is 0.1nm (2000× more than in the light microscope).

• This means the electron microscope can be used to produce detailed images

of the structures (organelles) inside cells.

• The SEM produces 3D images that can reveal the detail of contours and

cellular or tissue arrangements – this is not possible using light microscopes.

• Electron beams are defl ected by the molecules in air, so samples are placed

in a vacuum.

• Electron microscopes are extremely expensive items.

Coloured electron micrographs

Electron micrographs are sometimes shown in colour. The fi nal image produced from an

electron microscope is always black, white and grey; the colours are added afterward

using specialised computer software. Such images will be labelled as ‘false-colour’

electron micrographs.Figure 1 Electron micrograph of an

insect grasping a microelectronic

component in its mandibles

Figure 2 Electron microscope in outline

Electrongun

Condenserlenses

Projectionaperture

Stigmator

Scan coils

Objectivelens

Detector(ESD)

Specimenstub

Specimenstage

Specimenchamber

Gas inlet

Questions1 List the similarities and differences between light and electron microscopes.

2 Explain why both light and electron microscopes are used widely in biology.

3 Describe the main limitations of the electron microscope.

4 Describe the limitations of the light microscope.

Figure 3 Preparation and viewing of

samples for scanning electron

microscopy

Figure 4 False-colour electron micrographs of pollen grains and red blood cells

Examiner tip

You may be asked to calculate the

actual size of a specimen. Measure the

size of the image in mm and then

convert it to m. Then divide it by the

magnifi cation.

Key de� nition

Staining in microscopy refers to any

process that helps to reveal or

distinguish different features. In light

microscopy, stains may be colours or

fl uorescent dyes. In electron

microscopy, they are metal particles or

metal salts.

Preparing specimens to be viewed in an electron microscope is complicated.

For example, to prepare a thin section of liver tissue, you might need to:

• fi x the specimen in glutaraldehyde to make the tissue fi rm

• dehydrate it to replace the water with ethanol

• embed the dehydrated tissue in a solid resin

• cut very thin slices using a diamond knife

• stain it using lead salts to scatter electrons differently – this gives contrast

• mount it on a copper grid

• place the specimen on the grid in a vacuum in the microscope.

When electron microscopes were fi rst developed, many scientists thought that the

complicated preparation of specimens produced artefacts. Artefacts are structures that

result from the preparation process. They are not true representations of the

specimen’s original structure.

Even in the 1980s, scientists were arguing about the true value of electron microscopes,

but their technology and quality has improved in recent years. Scientists have also used

X-ray crystallography to investigate cell structure. This has confi rmed that electron

microscopes do give a true insight into the internal workings of cells.

How science works

4


AS



We listen to teachers’ needs...

Sample pages from OCR AS Biology Student Book.

Exclusively endorsed by OCR, these Student Books offer accessible and engaging material to help students understand the underlying principles of science. Careful explanations of key principles, plenty of worked examples, practice questions and exam-style questions all ensure that students have plenty of opportunities to improve their skills.

Examination tips.

Text is structured in line with the new OCR specification, by Unit and Module.

Integrates How Science Works throughout the book to help students understand the underlying principles of science.

82

83

Exercise/diet/smoking

Health aspects oflifestyle

Lungs

Exchange withcells

Tissue fluid

Blood vessels

Heart

Animals

Animals

Transpiration

Translocation

Leaves

Roots

Plants

Diffusion throughoutcell

Surface of body usedfor exchange

Exchange andtransport links

Digestivesystem

Low demand foroxygen and nutrients

Large surface-area-to-volume ratio

Single-celled organismsand small multicellular

organisms

Xylem

Plants

Phloem

Need fortransport

system

Need forspecial

exchangesurface

High demand foroxygen and nutrients

Small surface-area-to-volume ratio

Large multicellularorganisms

Living things

1.2 Exchange and transport summary

1 (a) State the names of the tissues labelled A–D below. [4]A

B

C

D

Figure 1

(b) Name the organ represented by Figure 1. [1]

2 (a) State the name of the type of muscle found in theheart.[1] (b) Explain why the muscle surrounding the left ventricle isthicker than that surrounding the right ventricle. [2] (c) Name the blood vessels that: (i) carry blood away from the ventricles; (ii) carry blood back towards the heart. [2]

3 (a) State two features of a good gaseous exchangesystem.[2] (b) Describe the route taken by air as it is inhaled. [3] (c) Name the air sacs in the lungs. [1]

4 (a) What immediate effect does exercise have on the heartrate?[1] (b) What happens to the tidal volume of the lungs duringexercise?[1] (c) Name two other exchange surfaces. [2]

5 Complete the following paragraph by filling in the blankspaces.Blood is .................................... in the lungs. The redpigment .................................. has a high affinity foroxygen. The pumping action of the ..........................creates pressure which pushes the blood around the body.In the tissues the partial pressure of ..................................is low. This causes the ................................ of theoxyhaemoglobin. In the tissues, the oxygen is used in theprocess of ................................. . Most of the carbondioxide produced in this process enters the.............................................. cells. Here it is converted to carbonic acidby the action of the enzyme carbonic anhydrase. Thecarbon dioxide is transported as .....................................back to the lungs.

[8]

6 (a) Explain the role of elastic tissue in the alveoli. [2] (b) Name the two types of cell found in the epithelium ofthe airways.[2] (c) Describe the action of the cilia in bronchi. [2]

7 (a) In a plant, name two tissues that may act as a source.[2] (b) Name the tissue that is used to transport sugars in aplant.[1]

8 (a) Explain why a large organism with a lowsurface-area-to-volume ratio needs a special surfacefor gaseous exchange.[3] (b) Explain how a higher concentration of carbon dioxidein the blood can cause extra oxygen to dissociate fromoxyhaemoglobin.[4]

9 (a) Describe how sucrose is loaded into the sieve tubeelement.[4] (b) Explain, using the term water vapour potential gradient,why increasing the wind speed will increase the rate oftranspiration.[3]

10 (a) Explain the importance of the Purkyne tissue incoordination of the cardiac cycle. [3] (b) Describe and explain the role of the coronary arteries.[3]

Practice questionsModule 2

Exchange and transportPractice questions

936 biology.U1 M2.indd 82-83

10/3/08 11:40:13 am

8

9

1.1 3 Electron microscopes and cell details

Module 1Cells

Electron microscopes and cell details

By the end of this spread, you should be able to . . .

State the magni� cation that can be achieved with the electron microscope.

Explain the need for staining samples for use in light microscopy and electron microscopy.

The use of electronsLight microscopes have low resolution. This means that if the magnifi cation is above

×1500, the image isn’t clear. The wavelength of visible light ranges from about 400 to

750nm, so structures closer together than 200nm (0.2 m) will appear as one object.

We can achieve higher resolution with electron microscopes.

• Electron microscopes generate a beam of electrons.

• A beam of electrons has a wavelength of 0.004nm, 100000 times shorter than a light

wavelength.

• Electron microscopes can distinguish between objects 0.2nm apart.

• These microscopes use magnets (instead of lenses) to focus the beam of electrons

onto a prepared specimen.

• Electrons are not visible to the human eye. The image produced from the

electron beam is projected onto a screen or onto photographic paper to make a

black-and-white image (sometimes referred to as a ‘greyscale’ image).

• Such images are called electron micrographs.

• The resolution of an electron microscope is about 500000 times greater than that of

the human eye.

Two types of electron microscope

Transmission electron microscope (TEM)

• The electron beam passes through a very thin prepared sample.

• Electrons pass through the denser parts of the sample less easily, so giving some

contrast.

• The fi nal image produced is two-dimensional.

• The magnifi cation possible with a TEM is ×500000.

Scanning electron microscope (SEM)

• The electron beam is directed onto a sample. The electrons don’t pass

through the specimen.

• They are ‘bounced off’ (refl ected off) the sample.

• The fi nal image produced is a 3D view of the surface of the sample.

• The magnifi cation possible with an SEM is about ×100000.

Advantages and limitations of the electron microscope

• The resolution is 0.1nm (2000× more than in the light microscope).

• This means the electron microscope can be used to produce detailed images

of the structures (organelles) inside cells.

• The SEM produces 3D images that can reveal the detail of contours and

cellular or tissue arrangements – this is not possible using light microscopes.

• Electron beams are defl ected by the molecules in air, so samples are placed

in a vacuum.

• Electron microscopes are extremely expensive items.

Coloured electron micrographs

Electron micrographs are sometimes shown in colour. The fi nal image produced from an

electron microscope is always black, white and grey; the colours are added afterward

using specialised computer software. Such images will be labelled as ‘false-colour’

electron micrographs.Figure 1 Electron micrograph of an

insect grasping a microelectronic

component in its mandibles

Figure 2 Electron microscope in outline

Electrongun

Condenserlenses

Projectionaperture

Stigmator

Scan coils

Objectivelens

Detector(ESD)

Specimenstub

Specimenstage

Specimenchamber

Gas inlet

Questions1 List the similarities and differences between light and electron microscopes.

2 Explain why both light and electron microscopes are used widely in biology.

3 Describe the main limitations of the electron microscope.

4 Describe the limitations of the light microscope.

Figure 3 Preparation and viewing of

samples for scanning electron

microscopy

Figure 4 False-colour electron micrographs of pollen grains and red blood cells

Examiner tip

You may be asked to calculate the

actual size of a specimen. Measure the

size of the image in mm and then

convert it to m. Then divide it by the

magnifi cation.

Key de� nition

Staining in microscopy refers to any

process that helps to reveal or

distinguish different features. In light

microscopy, stains may be colours or

fl uorescent dyes. In electron

microscopy, they are metal particles or

metal salts.

Preparing specimens to be viewed in an electron microscope is complicated.

For example, to prepare a thin section of liver tissue, you might need to:

• fi x the specimen in glutaraldehyde to make the tissue fi rm

• dehydrate it to replace the water with ethanol

• embed the dehydrated tissue in a solid resin

• cut very thin slices using a diamond knife

• stain it using lead salts to scatter electrons differently – this gives contrast

• mount it on a copper grid

• place the specimen on the grid in a vacuum in the microscope.

When electron microscopes were fi rst developed, many scientists thought that the

complicated preparation of specimens produced artefacts. Artefacts are structures that

result from the preparation process. They are not true representations of the

specimen’s original structure.

Even in the 1980s, scientists were arguing about the true value of electron microscopes,

but their technology and quality has improved in recent years. Scientists have also used

X-ray crystallography to investigate cell structure. This has confi rmed that electron

microscopes do give a true insight into the internal workings of cells.

How science works

5





A2

Don’t forget our A2 resources coming in the Autumn Term!

End-of-module summary pages help students link together all the topics within each module.

Practice exam questions provided at the end of each module. Answers are in the back of the book.

In our unique Exam Café, students will find plenty of support to help them prepare for their exams. They can Relax and prepare with handy revision advice, Refresh their memories by testing their understanding and Get That Result through practising exam-style questions, accompanied by lots of hints and tips.

An Exam Café CD-ROM is included FREE in the back of every Student Book.

6

Sample screen from OCR AS Biology Exam Café CD-ROM.

Links to how students can use New Scientist to reinforce their learning.

Sample questions and answers to each module with tips on how to improve, examiner tips and advice to students on practical skills.

Questions to test understanding. Also vocabulary tests, a glossary, and revision flashcards.

Study and revision skills to support students making the transition from GCSE to A Level.

What do students think about Exam Café?

“Three stages is a great idea – something you can work through.”

Sophie Wilson, student, Headington School.

“A really great and original way of encouraging students to revise and study for exams.”Marie-Lise Tassoni, student, Bexhill College.

“I think it’s an extremely positive idea to make students see their potential.”Sophie East, student, Oxford.

7

Student answer activities focus on improving subject knowledge.

Three stages allow students to see questions against answers and examiner feedback.

Links directly to the module and specification.

Sample screen from OCR AS Biology Exam Café CD-ROM.

Teacher Support CD-ROM

The AS and A2 Teacher Support CD-ROMs help you plan and deliver the new specification with confidence. Each provides you with:

l weekly teaching plans and guidance sheets to help save time

l customisable student practical sheets with accompanying teacher and technician notes

l a media bank of all the diagrams and learning objectives in the Student Book, all ready to use in PowerPoint format.

8

Sample Lesson Plan from OCR AS Biology Teacher Support CD-ROM.

Pete Kennedy and Frank Sochacki


AS



9

Sample screen from OCR AS Biology Teacher Support CD-ROM.

Pete KennedyFrank SochackiSue Hocking

Mark WinterbottomSeries Editor: Sue Hocking



A2

Easy-to-use content menu and search box to help you locate your required content.

Split into 30 Weekly Plans.

10

Revision Guides

l Clearly written and well designed to aid revision.

l Written by experienced examiners and tailored to the new specification.

l Packed with examiner tips.

l Targeted at ensuring understanding with quick-check questions on each topic and end of unit exam-style questions.

�

�

Hint

Phospholipids form a

bilayer: ‘heads out,

tails in’ – see page 5.

Quick check 1✔

Key words

fluid mosaic

hydrophobic

hydrophilic

phospholipid bilayer

partially permeableMod

ule

1

Module 1

1 Explain why membranes are described as fluid mosaic.

2 Explain how phospholipids and proteins influence the permeability of a cell surface

membrane.

3 Describe the distribution of membranes within animal and plant cells.

QUICK CHECK QUESTIONS ?

Cell surface membranes surround all cells and control what enters and leaves.

Membranes divide up the cytoplasm of eukaryotic cells into separate compartments.

Membranes are very thin

Membranes are visible in the TEM at magnifications of ×100 000 as two dark lines

separated by a clear space. The distance across the membrane is about 7 nm.

Membranes are made of two layers of phospholipid, known as a bilayer, plus protein.

The polar heads of the phospholipids are hydrophilic and are attracted to water. This is

why they face towards the cytoplasm and towards the exterior of the cell. Both these

areas are dominated by water. The hydrocarbon tails of the two layers are hydrophobic

and are held together by weak hydrophobic bonds. Proteins are scattered about the

membrane, and transmembrane proteins pass right through from one side to the other.

Carbohydrates are attached to protein and lipid, and face the outside of the cell. This

structure is called a fluid mosaic.

Component of cell

membrane

Functions

Phospholipidsform a bilayer that acts as a barrier between cytoplasm and cell exterior

are fluid, so components can move within the membrane

are permeable to non-polar molecules such as oxygen and fatty acids

are permeable to small polar molecules such as ethanol, water and carbon dioxide

are impermeable to ions and large polar molecules such as sugars and amino acids

Cholesterol (only in

eukaryotic cells – much

more in animal cells

than in plant cells)

stabilises the phospholipid bilayer by binding to polar heads and non-polar tails of phospholipids

controls fluidity by preventing phospholipids solidifying at low temperatures and becoming too fluid at

high temperatures

reduces permeability to water, ions and polar molecules

Proteinsare transmembrane proteins acting as channels and carriers

are receptors for chemicals made by other cells, e.g. hormones

Glycolipids and

glycoproteins

(lipids and proteins

with carbohydrate

chains attached)

are carbohydrate chains only found on the exterior surface of cell membranes

act as receptors for signalling molecules (e.g. hormones) and for drugs

act as cell surface markers that identify the cells to others (also known as cell surface antigens)

are involved in ‘sticking’ cells to one another (cell adhesion)

Functions of cell surface membranes

Membranes are partially permeable because some substances pass through but

others do not. The permeability of a membrane is determined by the phospholipids and

proteins. Membranes are selective about what passes through. Cell surface membranes:

act as a barrier to many water-soluble substances

keep many large molecules, such as enzymes, within the cell

are permeable to small molecules such as water, oxygen and carbon dioxide

are permeable to selected molecules such as glucose and ions

permit movement of substances by endocytosis and exocytosis

permit recognition by other cells, such as those of the immune system

provide receptors for signalling molecules such as hormones

are often extended into microvilli to provide a large surface area for the absorption

of substances by animal cells.

Membranes within cells

The membranes within cells:

divide the cell into compartments where functions can occur more efficiently

isolate potentially harmful enzymes in lysosomes

provide a large surface for pigments, such as chlorophyll, involved in photosynthesis

in chloroplasts

provide a large surface for holding the enzymes and coenzymes for forming ATP in

mitochondria and chloroplasts

surround vesicles that transport molecules between parts of the cell, e.g. that

transport proteins from rough endoplasmic reticulum to Golgi apparatus.

Cell membranes

Examiner tip

Most of the organelles

you need to recognise

are made of membrane

– see page 4.

Hint

Some proteins are

anchored in

membranes and do not

move; others move like

boats in a sea of

phospholipid.

Examiner tip

You should be able to

draw and label a

diagram of a

membrane like the one

in the figure at the

bottom of this page.

Examiner tip

Do not confuse

microvilli with cilia –

see pages 4 and 16.

Quick check 2✔

Quick check 3✔

Hint

When answering quick

check question 3, look

back to the table of

organelles on page 4.

Cell membranes

1UNIT

Outside

Carbohydrate chain

of glycoprotein

Phos

phol

ipid

bila

yer

Inside(cytoplasm)

Glycolipid

Glycoprotein

Why fluid mosaic?

Fluid: phospholipids are liquid – think of a membrane as like a thin layer of oil.

Mosaic: this is a picture

made of many small pieces

of tile. Proteins are like the

pieces of tile surrounded

by phospholipids, which

are like the cement holding

everything together.

The phospholipid bilayer is

split open to show the proteins

that pass right through the

membrane.

Hydrophilic head

Glycolipid

Carbohydrate part of

glycoprotein

Glycoprotein

7–10nm

CholesterolChannel protein Carrier protein

Hydrophobictail

Phos

phol

ipid

bila

yer

A cross-section through a cell surface membrane

Sample pages from OCR AS Biology Revision Guide.

Richard Fosbery and Ianto StevensSeries editor: Sue Hocking

AS




This revision guide is tailored to the OCR specification and exclusively

endorsed by OCR for GCE Biology. It is written by experienced examiners

and teachers, giving you:

complete coverage of the specification for the exams

content organised by module and unit to follow the structure of the

specification and exams bite-sized chunks of information to make it easier to organise your

revision time quick-check revision questions so that you can test your own

knowledge easily hints and tips from examiners to help you avoid common errors

lots of practice exam-style questions for each unit

all the answers to questions so that you can check that you’re on the

right track.Titles in this series:OCR AS Biology student book and exam café CD-ROM 978 0 435691 80 6

OCR A2 Biology student book and exam café CD-ROM 978 0 435691 90 5

OCR AS Biology Teacher Support CD-ROM978 0 435691 77 6

OCR A2 Biology Teacher Support CD-ROM978 0 435691 91 2

OCR AS Biology revision guide

978 0 435583 70 5

OCR A2 Biology revision guide

978 0 435583 73 6

AS

Second Edition

01865 888118

www.heinemann.co.uk

In Exclusive PartnershipI S B N 978-0-435583-70-5

9 7 8 0 4 3 5 5 8 3 7 0 5

Clearly linked to the specification.

Where appropriate, information is presented in tables or simple clear diagrams in order to aid understanding.

Enables students to check their knowledge and understanding. Answers are provided at the back of the book.

Hints and tips help students avoid common errors.

11

�

�

Hint

Phospholipids form a

bilayer: ‘heads out,

tails in’ – see page 5.

Quick check 1✔

Key words

fluid mosaic

hydrophobic

hydrophilic

phospholipid bilayer

partially permeableMod

ule

1

Module 1

1 Explain why membranes are described as fluid mosaic.

2 Explain how phospholipids and proteins influence the permeability of a cell surface

membrane.

3 Describe the distribution of membranes within animal and plant cells.

QUICK CHECK QUESTIONS ?

Cell surface membranes surround all cells and control what enters and leaves.

Membranes divide up the cytoplasm of eukaryotic cells into separate compartments.

Membranes are very thin

Membranes are visible in the TEM at magnifications of ×100 000 as two dark lines

separated by a clear space. The distance across the membrane is about 7 nm.

Membranes are made of two layers of phospholipid, known as a bilayer, plus protein.

The polar heads of the phospholipids are hydrophilic and are attracted to water. This is

why they face towards the cytoplasm and towards the exterior of the cell. Both these

areas are dominated by water. The hydrocarbon tails of the two layers are hydrophobic

and are held together by weak hydrophobic bonds. Proteins are scattered about the

membrane, and transmembrane proteins pass right through from one side to the other.

Carbohydrates are attached to protein and lipid, and face the outside of the cell. This

structure is called a fluid mosaic.

Component of cell

membrane

Functions

Phospholipidsform a bilayer that acts as a barrier between cytoplasm and cell exterior

are fluid, so components can move within the membrane

are permeable to non-polar molecules such as oxygen and fatty acids

are permeable to small polar molecules such as ethanol, water and carbon dioxide

are impermeable to ions and large polar molecules such as sugars and amino acids

Cholesterol (only in

eukaryotic cells – much

more in animal cells

than in plant cells)

stabilises the phospholipid bilayer by binding to polar heads and non-polar tails of phospholipids

controls fluidity by preventing phospholipids solidifying at low temperatures and becoming too fluid at

high temperatures

reduces permeability to water, ions and polar molecules

Proteinsare transmembrane proteins acting as channels and carriers

are receptors for chemicals made by other cells, e.g. hormones

Glycolipids and

glycoproteins

(lipids and proteins

with carbohydrate

chains attached)

are carbohydrate chains only found on the exterior surface of cell membranes

act as receptors for signalling molecules (e.g. hormones) and for drugs

act as cell surface markers that identify the cells to others (also known as cell surface antigens)

are involved in ‘sticking’ cells to one another (cell adhesion)

Functions of cell surface membranes

Membranes are partially permeable because some substances pass through but

others do not. The permeability of a membrane is determined by the phospholipids and

proteins. Membranes are selective about what passes through. Cell surface membranes:

act as a barrier to many water-soluble substances

keep many large molecules, such as enzymes, within the cell

are permeable to small molecules such as water, oxygen and carbon dioxide

are permeable to selected molecules such as glucose and ions

permit movement of substances by endocytosis and exocytosis

permit recognition by other cells, such as those of the immune system

provide receptors for signalling molecules such as hormones

are often extended into microvilli to provide a large surface area for the absorption

of substances by animal cells.

Membranes within cells

The membranes within cells:

divide the cell into compartments where functions can occur more efficiently

isolate potentially harmful enzymes in lysosomes

provide a large surface for pigments, such as chlorophyll, involved in photosynthesis

in chloroplasts

provide a large surface for holding the enzymes and coenzymes for forming ATP in

mitochondria and chloroplasts

surround vesicles that transport molecules between parts of the cell, e.g. that

transport proteins from rough endoplasmic reticulum to Golgi apparatus.

Cell membranes

Examiner tip

Most of the organelles

you need to recognise

are made of membrane

– see page 4.

Hint

Some proteins are

anchored in

membranes and do not

move; others move like

boats in a sea of

phospholipid.

Examiner tip

You should be able to

draw and label a

diagram of a

membrane like the one

in the figure at the

bottom of this page.

Examiner tip

Do not confuse

microvilli with cilia –

see pages 4 and 16.

Quick check 2✔

Quick check 3✔

Hint

When answering quick

check question 3, look

back to the table of

organelles on page 4.

Cell membranes

1UNIT

Outside

Carbohydrate chain

of glycoprotein

Phos

phol

ipid

bila

yer

Inside(cytoplasm)

Glycolipid

Glycoprotein

Why fluid mosaic?

Fluid: phospholipids are liquid – think of a membrane as like a thin layer of oil.

Mosaic: this is a picture

made of many small pieces

of tile. Proteins are like the

pieces of tile surrounded

by phospholipids, which

are like the cement holding

everything together.

The phospholipid bilayer is

split open to show the proteins

that pass right through the

membrane.

Hydrophilic head

Glycolipid

Carbohydrate part of

glycoprotein

Glycoprotein

7–10nm

CholesterolChannel protein Carrier protein

Hydrophobictail

Phos

phol

ipid

bila

yer

A cross-section through a cell surface membrane




AS







A2

Summary of contents

iv

v

Introductionvi

UNIT 1 Cells, exchange and transport (F211)Module 1 Cells

21 Living organisms consist of cells 42 Cell size and magnification 63 Electron microscopes and cell details 84 Cells and living processes 105 Organelles – structure and function 126 Organelles at work147 Biological membranes – fluid boundaries 168 The fluid mosaic model 189 Communication and cell signalling 2010 Crossing membranes 1 – passive processes 2211 Crossing membranes 2 – active processes 2412 Water is a special case

2613 New cells – parent and daughter cells 2814 Two nuclei from one3015 Cell cycles and life cycles are not all the same 3216 Cell specialisation3417 Organising the organism 36Summary and practice questions 38End-of-module examination questions 40

Module 2 Exchange and transport 421 Special surfaces for exchange 442 The lung as an organ of exchange 463 Tissues in the lungs484 Measuring lung capacity 505 Transport in animals526 The structure of the mammalian heart 547 The cardiac cycle568 Control of the cardiac cycle 589 Blood vessels6010 Blood, tissue fluid and lymph 6211 Carriage of oxygen6412 Carriage of carbon dioxide 6613 Transport in plants6814 Xylem and phloem7015 Plant cells and water7216 Water uptake and movement up the stem 74

17 Transpiration7618 Reducing water loss – xerophytes 7819 The movement of sugars – translocation 80Summary and practice questions 82End-of-module examination questions 84

UNIT 2 Molecules, biodiversity, food and health (F212)Module 1 Biological molecules 861 Biochemistry and metabolism 882 Biochemicals and bonds 903 Carbohydrates 1: simple sugars 924 Carbohydrates 2: energy storage 945 Carbohydrates 3: structural units 966 Amino acids – the monomers of proteins 987 Proteins from amino acids 1008 Levels of protein structure 1029 Proteins in action

10410 Lipids are not polymers 10611 Essential oils?10812 Water – a vital biological molecule 11013 Practical biochemistry – 1 11214 Practical biochemistry – 2 11415 Nucleotides – coding molecules 11616 DNA – information storage 11817 Reading the instructions 12018 Enzymes are globular proteins 12219 Inside and out – where enzymes work best 12420 Enzyme action

12621 Enzymes and temperature 12822 Enzymes at work – pH effects 13023 Enzymes at work – concentration effects 13224 Enzymes at work – inhibitors of action 13425 Enzymes at work – coenzymes and prostheticgroups13626 Interfering with enzymes – poisons and drugs 13827 Investigating enzyme action – 1 14028 Investigating enzyme action – 2 14229 Enzymes and metabolism – an overview 144Summary and practice questions 146End-of-module examination questions 148

Module 2 Food and health 1501 Nutrition1522 Diet and coronary heart disease 1543 Improving food production 1564 Microorganisms and food 1585 Organisms that cause disease 1606 Transmission of diseases 1627 The worldwide importance of certain diseases 1648 Non-specific responses to diseases 1669 Antibodies

16810 Communication between cells 17011 The specific immune response 17212 Vaccination17413 Finding new drugs17614 The effects of smoking 17815 Smoking – nicotine and carbon monoxide 18016 Cardiovascular diseases 18217 The evidence linking smoking to disease 184Summary and practice questions 186End-of-module examination questions 188

Module 3 Biodiversity and evolution 1901 Biodiversity1922 Sampling plants194

3 Sampling animals1964 Measuring biodiversity 1985 Classification and taxonomy 2006 The five kingdoms

2027 Classifying living things 2048 Naming living things2069 Modern classification20810 Variation21011 Adaptation21212 Natural selection21413 The evidence for evolution 21614 Evolution today21815 Conservation of species 22016 The effect of global climate change 22217 Conservation in situ

22418 Conservation ex situ22619 International cooperation 228Summary and practice questions 230End-of-module examination questions 232

Answers234Glossary256Index268

ContentsContents

936 biology.prelims.indd 4-5

10/3/08 11:35:26 am

iv

v

Introductionvi

UNIT 1 Cells, exchange and transport

(F211)Module 1 Cells

2

1 Living organisms consist of cells 4

2 Cell size and magnification 6

3 Electron microscopes and cell details 8

4 Cells and living processes 10

5 Organelles – structure and function 12

6 Organelles at work14

7 Biological membranes – fluid boundaries 16

8 The fluid mosaic model 18

9 Communication and cell signalling 20

10 Crossing membranes 1 – passive processes 22

11 Crossing membranes 2 – active processes 24

12 Water is a special case26

13 New cells – parent and daughter cells 28

14 Two nuclei from one30

15 Cell cycles and life cycles are not all the same 32

16 Cell specialisation34

17 Organising the organism 36

Summary and practice questions 38

End-of-module examination questions 40

Module 2 Exchange and transport 42

1 Special surfaces for exchange 44

2 The lung as an organ of exchange 46

3 Tissues in the lungs48

4 Measuring lung capacity50

5 Transport in animals52

6 The structure of the mammalian heart 54

7 The cardiac cycle56

8 Control of the cardiac cycle 58

9 Blood vessels60

10 Blood, tissue fluid and lymph 62

11 Carriage of oxygen64

12 Carriage of carbon dioxide 66

13 Transport in plants68

14 Xylem and phloem70

15 Plant cells and water72

16 Water uptake and movement up the stem 74

17 Transpiration76

18 Reducing water loss – xerophytes 78

19 The movement of sugars – translocation 80



UNIT 2 Molecules, biodiversity, food

and health (F212)

Module 1 Biological molecules 86

1 Biochemistry and metabolism 88

2 Biochemicals and bonds 90

3 Carbohydrates 1: simple sugars 92

4 Carbohydrates 2: energy storage 94

5 Carbohydrates 3: structural units 96

6 Amino acids – the monomers of proteins 98

7 Proteins from amino acids 100

8 Levels of protein structure 102

9 Proteins in action104

10 Lipids are not polymers 106

11 Essential oils?108

12 Water – a vital biological molecule 110

13 Practical biochemistry – 1 112

14 Practical biochemistry – 2 114

15 Nucleotides – coding molecules 116

16 DNA – information storage 118

17 Reading the instructions 120

18 Enzymes are globular proteins 122

19 Inside and out – where enzymes work best 124

20 Enzyme action126

21 Enzymes and temperature 128

22 Enzymes at work – pH effects 130

23 Enzymes at work – concentration effects 132

24 Enzymes at work – inhibitors of action 134

25 Enzymes at work – coenzymes and prosthetic

groups136

26 Interfering with enzymes – poisons and drugs 138

27 Investigating enzyme action – 1 140

28 Investigating enzyme action – 2 142

29 Enzymes and metabolism – an overview 144



Module 2 Food and health 150

1 Nutrition152

2 Diet and coronary heart disease 154

3 Improving food production 156

4 Microorganisms and food 158

5 Organisms that cause disease 160

6 Transmission of diseases 162

7 The worldwide importance of certain diseases 164

8 Non-specific responses to diseases 166

9 Antibodies168

10 Communication between cells 170

11 The specific immune response 172

12 Vaccination174

13 Finding new drugs176

14 The effects of smoking 178

15 Smoking – nicotine and carbon monoxide 180

16 Cardiovascular diseases 182

17 The evidence linking smoking to disease 184



Module 3 Biodiversity and evolution 190

1 Biodiversity192

2 Sampling plants194

3 Sampling animals196

4 Measuring biodiversity198

5 Classification and taxonomy 200

6 The five kingdoms202

7 Classifying living things 204

8 Naming living things206

9 Modern classification208

10 Variation210

11 Adaptation212

12 Natural selection214

13 The evidence for evolution 216

14 Evolution today218

15 Conservation of species 220

16 The effect of global climate change 222

17 Conservation in situ224

18 Conservation ex situ226

19 International cooperation 228



Answers234

Glossary256

Index268

Contents

Contents

936 biology.prelims.indd 4-5

10/3/08 11:35:26 am

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