UNIT THREE

UNIT THREE

BIOLOGYAREA OF STUDY #1: MOLECULES OF LIFE

EXAM REVISION LECTURE

CHP 2: MEMBRANES AND CELL ORGANELLES

Cell TypesViruses: not really cells; share some characteristics with living things including;

– Genetic material (DNA or RNA)– Protein coat (known as a capsid); some also envelop themselves courtesy of infected host membrane– Enzymes

Prokaryotic Cells: • Include bacteria (Monera), archaebacteria and eubacteria• Smallest living cells (most bacteria less than 1 micron i.e. <1/1000mm)• All single celled organisms (but some form colonies)• Have a cell membrane and cytosol• Lack membrane bound organelles• Have no nuclear membrane• Have just one, circular chromosome; may have many small rings of DNA called plasmids• contain ribosomes (organelle not membrane bound)• May contain fimbria (hairline structures used for attachment); flagellum - used for movement

CHP 2 TOPIC 1: CELLS

Eukaryotic Cells• Larger than prokaryotic cells (ranging from 10 to 150 microns)• Include the Kingdoms: animal; plants; fungi & protista (protozoa)• Some are unicellular (single celled) others are multicellular (with many specialised cells)• All contain membrane bound organelles suspended in a fluid known as cytosol• (membranes, organelle and cytosol together is known as cytoplasm• Membrane is a liquid lipid bilayer (two layers of phospholipids)• Have many linear chromosomes

Protista Cells• eukaryotic – have a nucleus• example: paramecium; euglena, amoeba• unicellular• about 100 microns• cell membrane • may contain chloroplasts; cell wall

Fungi Cells • eukaryotic• can be single or mutlicellular• cell wall – made of chitin • cell membrane

Plant Cells• eukaryotic • multicellular – often square in shape• cell membrane (often not visible)• cell wall made of cellulose• some cells contain plastids (i.e. chloroplasts)• vacuoles

Animal Cells• eukaryotic• multicellular• no cell wall or vacuole• centrioles (involved in cell division)•

The light microscope has a limit of resolution of

about 200 nm (0.2 µm). This limit is due to the

wavelength of light (0.4-0.7 µm). Cells observed

under a light microscope can be alive, or fixed and

stained

Topic CHP2.1 Questions:1. List up to 7 characteristics of all living things:

2. Which of the following would be not be visible under a low-power light microscope:Guard Cell; White Blood Cell; paramecium; nucleus; ribosome

3. Which of the following could be used to examine living cells:3. Light microscope or Transmission Electron Microscope

4. List three characteristics of each of the following:3. Protozoan Cell: ___________________, ________________________ & ________________________4. Bacteria Cell: : ___________________, ________________________ & ________________________5. Plant Cell: : ___________________, ________________________ & ________________________

5. True False: Bacteria, Plant & Fungi cell walls are made of polysaccharides6. True False : The cell wall of Fungi is made of chitin7. True/ False: Plasmids are circular units of DNA8. What name is given to inert viruses (those not infecting a host): _______________9. What name is given to the protein coat around a viruse: _____________________

/ 9 Marks

Organelle: structural unit in cells that performs a key function in cellular metabolism

CHP 2 TOPIC 2: CELL ORGANELLES

Name & Location

Description/ Diagram Function Present in

Prokaryotes Animal Plants

Cell Membranealso called: cytoplasmic/ plasma membrane

Double layer of phospholipids embedded with proteins, glycoproteins and carbohydrates

• encloses cell contents• regulates the movement of materials into and out of cells• maintain cell shape• communicate with other cells √ √ √

Nucleus Surrounded by a double membrane (2 membranes!).

Contains chromosomes and nucleolus

Some cells have more than 1

• information in the chromosomes controls the production of proteins in the cell- control cellular metabolism

x √ √

Nuclear Membrane

Pores in membrane big enough for RNA to leave

• regulates the movement of materials between itself x √ √

CHP 2 TOPIC 2: CELL ORGANELLESName & Location



Nucleolus1-3 inside a nucleus

A granular structure in the nucleus, made up of protein and RNA

• site of manufacture of ribosomal RNA x √ √

Mitochondria(sing: mitochondrion)

A few to thousands in cytoplasm

Sacs made up of 2 membranes . Inner membrane folded to create cristae (increase SA: V).Fluid filled matrix

• site of aerobic cellular respiration, they are responsible for most of the cells energy production

• most abundant in cells with high energy needs; muscle cells, kidney tubules

x √ √




RibosomesSome are free in the cytosol (produce protein for cell)

others are free floating (proteins for export)

Small spherical organelles composed of RNA and proteinConsist of two sub-units

• the site of protein synthesis

√ √ √

Smooth Endoplasmic Reticulumthroughout the cytoplasm

Network of membranes creating channels in the cytoplasm from the nucleus to the cell membrane

• the site of lipid synthesis •transport of many materials throughout the cell. Abundant in cells which produced steroid hormones•also contains enzymes for detoxifying chemicals including drugs and pesticides

x √ √




Nucleolus1-3 inside a nucleus

A granular structure in the nucleus, made up of protein and RNA

• site of manufacture of ribosomal RNA x √ √

Mitochondria(sing: mitochondrion)

A few to thousands in cytoplasm

Sacs made up of 2 membranes . Inner membrane folded to create cristae (increase SA: V).Fluid filled matrix

• site of aerobic cellular respiration, they are responsible for most of the cells energy production

• most abundant in cells with high energy needs; muscle cells, kidney tubules

x √ √




Rough Endoplasmic Reticulumthroughout the cytoplasm

Often associated with nuclear memb.

A network of membranes creating channels in the cytoplasm.Studded with ribosomes

• transport and folding of proteins produced by ribosomes• synthesis of gycoproteins• parts become pinched off to become vesicles for transport to the membrane or to other organelles

x √ √

Golgi Complexalso called golgi complex

Stacks of flattened sacs

• packages proteins and glycoproteins into vesicles for secretion from the cell or to be sent to other organelles•Synthesises cellulose in plant cells• abundant in cells that export cell products

x √ √




Lysosomethroughout cytoplasm

A membrane sack containing many digestive enzymes

• contain enzymes which digest ingested materials and wastes. Important in programmed cell death (apoptosis)

x √ x

VacuoleOne large in mature plant cells. Smaller (vesicles) in animal cells)Appear clear when seen through a microscope

A membrane bound sac containing fluid, sugars and ions

• important in cell turgor in plant cells

• pressure of fluid in large vacuole helps maintain cell shape

• storage storage of sugars, ions and food

x √ √




ChloroplastsFew to many in cells which photosynthesis

Surrounded by a double membrane, contains stacks of membranes (grana) embedded in less dense membrane and fluid (stroma)

• site of photosynthesis

• grana (or thylakoid membranes) contain chlorophyll, the pigment which traps light energy

•Abundant in leaf cells

x x √

CentrioleNear the nucleus in animal cells

Near the poles in dividing animal cells

A pair of cylindrical structures made up of several smaller tubes

•The spindle forms between centrioles during cell division

x √ x




Flagella or CiliaExtension(s) of the cell membrane

Made of membrane material and microtubules, they protrude from the cell.

Note, prokaryotic flagella lack membrane material

• provides a means of movement of the cell or of the fluid surrounding the cell

√ √ √

Cell Wall (not really an organelle!)

A layer of cellulose (in plants) secreted by the cell (see golgi complex) and completely surrounding membrane.Note: cellulose only in plant cells

• provides structural support and defines the shape of cells

√ x √

Topic CHP2.2 Questions:1. The cellular organelles which assemble polypeptides are called? _________________2. Pancreatic cells will incorporate radioactively labelled amino acids into proteins. Proteins can therefore be

labelled and tracked within a cell. If we were tracking a pancreatic enzyme that was to be secreted, the most likely pathway of movement of this protein in the cell would be:

A. Endoplasmic reticulum to golgi body to nucleusB. Golgi body to ER to lysosomeC. Nucleus to ER to golgi bodyD. ER to golgi body to secretory vesicles

3. The purpose of the cristae in mitochondria isA. To provide greater SA within the organelleB. To store chemicalsC. To provide a surface for the process of photosynthesis to occurD. To provide structural support

4. Rough ER are called rough because: ______________5. In what type of plant cells would you expect to find mitochondria? _____________6. Which 4 organelles contain nucleic material? _____________________________________7. Outline the role of the following organelles in protein manufacture:

– Nucleus– Ribosomes– Rough ER– Golgi Apparatus– Secretory vesicles

8. True/ False: Lysosmes are involved in apoptosis? 9. Which organelles have a double membrane?__________________________________________10. Name three organelles you can see and three you can’t see under a light microscope in an animal cell.

____________________________________, ________________________________, _______________________________

/ 10 Marks

A catalyst is any chemical which speeds up the rate of a chemical reaction without itself being used up in the reaction. Biological catalysts are enzymes.

Enzymes are protein molecules manufactured by cells in the ribosomes.

CHP 2 TOPIC 3 ENZYMES

• are proteins that act on other molecules• are organic catalysts • are protein molecules that increase the rate of reactions that occur inside the

organism.• are generally intracellular (exception: digestive enzymes)• some require a non-protein cofactor (i.e vitamins, CoQ10) before they can act• have a region, known as the active site, that alligns with a particular substrate• the compounds obtained as a result of the enzyme action are called the products• enzymes are highly specific in their action. Each enzyme acts on a particular

substrate.

Substrate

Enzyme

Active Site

Enzyme-Substrate ComplexProduct

Enzyme

1

23

Enzymes are organic

catalysts.

Menu

• Many enzymes lower the activation energy required to get a reaction going• Enzymes are sensitive to pH. They will only work in optimum pH range• Optimum pH differs for different enzymes• Enzymes are denatured if the pH varies from the optimum• Enzymes are temperature sensitive• Most enzymes work best at temps between 35-40 degrees celcius• The rate of any reaction is slower at lower temps• At temps above 40 degrees most enzymes denature• Some bacterial enzymes can exist in hot temps• Enzyme action can be affected by the presence of other molecules which may

inhibit the action of the enzyme• Inhibition of enzymes may be reversible or irreversible

REVERSIBLE INHIBITION Competitive Inhibition: molecule competes with the substrate for binding to the enzymes active site – temporary

Non-Competitive Inhibition: Molecule binds with the enzyme in a part of the enzyme that is not the active site, but alters the shape of the enzyme molecule

IRREVERSIBLE INHIBITION

Denaturing; caused by heat, pH or other chemicals the seondary or tertiary structure is lost

Binding of Poisons: many pisons are chemicals which bind irreversibly to enzymes, stopping their function. Examples: some antibiotics, gases, heavy metals

• Cofactors: some enzymes require another chemical component attached to the protein to be active:

• Some cofactors are inorganic ions• Organic cofactors are called coenzymes • Most coenzymes are carrier molecules transferring electrons or ions from one

reactant to another in a biological reaction: NADH, NADPH and FADH2 are important coenzymes ATP is a coenzyme

This complementary fitting of shapes is known as the ‘lock and key’ theory of enzyme action.

in some cases, the shape of the active site varies slightly from that of the substrate and the two fit only after the

substrate induces a complimentary shape at the active

site theory of enzyme action.

Rate of reaction will be dependent upon amount of:

• substrate concentration• enzyme concentration• cofactors concentration• presence of inhibitors such as poisons

Topic CHP2.3Questions:1. Name four factors that influence that rate of enzyme action: ________________,_________________, ______________________ & ______________________2. The amount of energy required to initiate a reaction is called what: _______________________3. A biological catalyst is called an: _____________________4. In regards to enzyme inhibition, denaturing is: reversible / irreversible5. A molecule which competes with the substrate for binding to the ensymes active

site is called what: ___________________ _________________6. The action of enzymes is: random/ dependent upon diploar bonds/ highly specific7. With regards to theories of enzyme action, the perfect fit of enzyme and substrate

is called the ________________ theory; when the substrate is slightly different to that of the active site, the theory of enzyme action is known as the ___________ & ______________ theory

/ 7 Marks

CHP 2 TOPIC 4 MEMBRANES & MOVEMENT OF MATERIALS• All cells are surrounded by a cellular membrane (also known as plasma membrane)• Cell membranes are selectively/ semi/ partially permeable• Control movement into and out of cell; communication between cells; recognition

by other cells• Less than 0.01 microns thick or 1/ 100 000 mm or 10 nanometers (scanning

electron can see down to 2 nanometers!)• Cell membranes are composed of a phospholipid bilayer• Proteins are embedded in the bilayer• Carbohydrate chains are involved in cell recognition• Cholesterol (lipid- steroid) also often embedded in membrane- aide fluidity• The phospholipids and proteins allow the movement of substances in and out of cell

These proteins are used in intercellular

communication. In this animation you can see the a hormone binding

to the receptor. This causes the receptor

protein release a signal to perform some

action.

Receptor Proteins

There are carrier proteins that regulate transport and diffusion

Channel Proteins

Topic CHP2.4 Questions:1. List four roles for cell membranes:____________, ______________, __________,______________2. List 5 molecules found in a typical cell membrane::____________,

______________, __________,______________ & __________________3. True/ false: you can see a membrane under a scanning electron microscope ?

_________________

/ 3 Marks

Diffusion is the ‘tendency’ of particles of gases, liquids and solutes to dispense randomly and fill available space– Rate of diffusion increases with: temperature increase/ concentration increase– Particles random movement from where they are in high concentration to were they are

in low concentration– This is commonly referred to as moving along a concentration gradient – Diffusion does not require energy – passive transport– Does not have to occur through a permeable membrane

CHP 2 TOPIC 5 MOVEMENT OF MATERIALS THROUGH MEMBRANES


Osmosis is the net movement of water molecules across a differentially permeable membrane, from an area of low solute concentration to an area of high solute concentration).

note: you don’t usually refer to water with the word concentration

– Water can only move passively (through osmosis)– Water (H2O)molecules are smaller glucose (C6H12O6) etc and can move readily– The net movement is ‘overall’ as water moves both directions– When water is in solution, solutes often combine (NACl) and reduce ability of water to move– Intercellular fluid surrounding cells is usually isotonic (the same) asthe intracellular fluid (in cell

Surrounding cell Animal cell Plant cell

Isotonic solution- solute concentration the same as cell

Water moves into and out of the cell at the same rate- no net movement

Water moves into and out of the cell at the same rate- no net movement

Hypotonic solution –a lower solute concentration than cell

Water enters the cell causing it to swell. Too much osmotic pressure - it bursts

Water enters cells and passes into vacuole. Vacuole squeezes cytoplasm against cell wall. Cell becomes turgid

Hypertonic solution – higher solute concentration than the cell

Net movement of water out of cell, causing shrinkage. Cell may die

Water leaves cell causing plasmolysis (shrinkage). Cell becomes flacid.


Movement Type Description Direction Of Movement

Active/ Passive

Simple Diffusion Small uncharged particles (water, oxygen) and lipid soluble (alcohol, urea) molecules diffuse from an area of high to low concentration through phospholipid bilayer

High to Low solute Passive

Channel Mediated /

Facilitated Diffusion

In some cases the channel proteins simply act as a passive pore. Molecules will randomly move through the opening in a process called diffusion. Ions, glucose, amino acids

Passive

Active Transport The transport of molecules across cell membranes against a concentration gradient. Active transport occurs through protein channels and requires energy in the form of ATP I.e. potassium ions ,

Low to highActive

EndocytosisPinocytosis (fluid) and

phagocytosis large particles and debris)

Cells are able to take in larger quantities of solids and liquids by endocytosis. Parts of the membrane fold around the material and pinch off, inclosing the material in a vesicle.Process requires energy

Active

Exocytosis Cells secrete cell products and eliminate wastes by exocytosis.vesicles fuse with membrane, open out and spilll contents into intercellular fluid. Process requires energy

Active

High to Low solute

High to Low solute

Topic CHP2.5 Questions:1. Name two factors that can influence the rate of diffusion: _______________, ____________ 2. Diffusing particles: move along/ against/ up a concentration gradient3. True/ False: Diffusion does not require ATP4. True/ False: Diffusion take place through a differentially permeable membrane5. True / False: Water can be moved against a concentration gradient with the use of ATP6. Which of the following is the larger molecule (circle): a monosaccharide/ water7. Name three factors that influence the net movement of water molecules through a

differentially permeable membrane: _______________, ____________ & _______________8. Fresh water fish cells would be (circle): isotonic/ hypertonic/ hypotonic in comparison to

their environment9. Cells of a salt water fish placed into freshwater would: expand & burst/ shrivel10. Plant cells placed in a hypertonic solution will undergo: plasmolysis/ become turgid11. pressure caused by water within the cell is called: ______________ pressure 12. Active transport requires which of the following: protein channels, ATP Synthase, ATP,

concentration gradient13. True/ False: Facilitated Diffusion/ Channel mediated diffusion requires ATP14. Name two forms of Exocytosis:____________________ & _______________________15. Name four molecules that can move through a phospholipid bilayer by simple diffusion:__________________, _______________________, __________________, _____________

/ 15 Marks

Chapter 2 - Cells: Structure & Function 30

• A few types of cells are large enough to be seen by the unaided eye.

• The human egg (ovum) is the largest cell in the body, and can (just) be seen without the aid of a microscope.

• Most cells are small for two main reasons: a). The cell’s nucleus can only control a certain volume of active cytoplasm.

b). Cells are limited in size by their surface area to volume ratio. A group of small cells has a relatively larger surface area than a single large cell of the same volume. This is important because the nutrients, oxygen, and other materials a cell requires must enter through it surface.

As a cell grows larger at some point its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell's need. (= Fick’s Law – something you need to learn well).

– Rate of diffusion α Surface Area x Concentration Difference Distance

CHP 2 TOPIC 6 SURFACE AREA TO VOLUME & CELL SIZE

Chapter 2 - Cells: Structure & Function 31

CHP 2 TOPIC 6 SURFACE AREA TO VOLUME & CELL SIZECellular environments and cell sizeAll cells need to exchange materials with their environments. They need to take in gases, water and nutrients and get rid of wastes. Exchange of materials can only occur through the cell’s membrane. The larger a cell becomes, the smaller its surface area becomes in relation to its volume. Look at these cubes to see the difference increasing size has on the ratio between surface area and volume

When a cell grows its volume grows at a greater rate than its surface area. If a cell

becomes to large they are unable to carry out sufficient exchange of materials with the environment.

Q. how would Fick’s Law influence the potential size of Prokaryotic organisms?

Topic CHP2.6 Questions:1. Name on cell visible with the naked eye? ______________2. List two factors that limit cell size:________________________, ______________3. As a cell grows larger at some point its surface area becomes too small to allow

these materials to enter the cell quickly enough to meet the cell's need. This is known as_____________________ Law

4. Find the SA: V of the following:

5. Which cube has the greater SA:V?

In most multicellular organisms, we find the following organization:

• Cellular Level: The smallest unit of life capable of carrying out all the functions of living things.

• Tissue Level: A group of cells that performs a specific function in an organism.

• Organ Level: Several different types of tissue that function together for a specific purpose.

• Organ System Level: Several organs working together to perform a function. The different organ systems in a multicellular organism interact to carry out the processes of life

CHP 2 TOPIC 7 CELL SPECIALISATIION -TISSUES ORGANS & SYSTEMS

Eukaryotic cells vary a great deal in structure. Variations in cell structure are related to function.Cells vary in the number of each organelle present and in their shape and life cycle.

CHP 2 TOPIC 7 CELL SPECIALISATIION -TISSUES ORGANS & SYSTEMS

Function Example Structure

Absorption of materialsA cell lining the intestine Large surface area created by folds of

membrane known as microvilli. Large number of mitochondria to provide energy for active transport

A root hair cell Large surface area due to long, elongated shape. Large number of mitochondria to provide energy for active transport

Photosynthesis A leaf cell Large number of chloroplasts, large vacuole for water storage

Communication A motor neuron Elongated shape, large number of mitochondria for energy production

Transport A sieve tube cell (plant vascular bundle)

Cells of the phloem vessels in plants have thickened cell walls, elongated shape and porous ends

Topic CHP2.7 Questions:

1. True/ False: cells in an organ are all made of the same tissue and cell type? ______2. How do single celled organisms function without specialised cells and tissues?

Explain: _________________________________________________________________________________________________________________________________________________________________________________________________________

3. Name two characteristics of:– root hairs that supports its function to absorb materials from its environment: _______________,

____________________– Microvilli that supports its function to absorb materials from its environment: _______________,

____________________– Leaf cell to photosynthesise: _______________, ____________________

/ 3 Marks

Although some cells like blood cells, are free to move as individuals around the body, most cells remain as a group. To assist this ‘community’ of cells are three types of junctions (joins) including:

– Occluding junctions: simply where one cell comes into contact with another (no movement of material between them)

– Communicating junctions (gap junctions): also known as gap junctions. Consist of

protein lined pores between the membrane of adjacent cells. The proteins are aligned like a series of rods with a gap (pore) in the middle of them. This bridge between cells enables the passage of ions, sugars, amino acids, other small particles and even electrical signals between the two cells. (example: electrical impulse in the heart)

– Anchoring Junctions (desmosomes): most common form of junction in epithelial cells (skin, uterus, lining cells!). Dense proteins protrude from the cytosol of one cell into the other to ‘anchor’ the cells together.

CHP 2 TOPIC 8 CONNECTIONS BETWEEN CELLS

• Communicating Junctions right ..

• Anchoring junctions below

Chapter 2 - Membranes and cell organelles

37

• Plasmodesmata (singular: plasmodium) is the name given for the structure that joins plant cells. Because of the way in which cell walls are built, the gap or pore between two cells is continuous and lined with cell membrane. The structure that bridges the gap is continuos with smooth endoplamsic reticulum.

Chapter 2 - Membranes and cell organelles

38

Connections between plant cells

Topic CHP2.8 Questions:1. List three types of communicating junctions:____________________, ___________________________, _________________2. What is the name given to the structure that joins plant cells together:__________________3. True/ False: the cytoplasm of one plant cell is continuous with the cytoplasm of

another plant cell4. Which macromolecule constitutes the gap junction structure: ________________5. Name this structure: Dense proteins protrude from the cytosol of one cell into the

other to anchor the cells together: ____________________

/5 Marks

Date post:	22-Mar-2016
Category:	Documents
Upload:	yates
View:	29 times
Download:	1 times

UNIT THREE

Documents