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192 Cards in this Set

  • Front
  • Back

What is magnification?

How much bigger an image looks compared with the original object.

What is resolution?

The ability of an optical instrument to see or produce an image that shows detail clearly.

Light microscope

Max mag 2000x

Resolution 200nm

Light microscope pros and con


Easy to use


Able to study live specimens

Limited resolution

Laser scanning microscopes

Max mag approx 2000x

High resolution

Displayed on a computer

Best for looking at living cells

Can focus on structures at different depths

Laser scanning microscopes cons

Low resolution compared to electron microscope

Not portable


Transmission election microscopes TEM

Max mag approx 5,000,000x

Very high resolution

Best for looking at internal structure of objects

Transmission election microscopes TEM cons

Can’t be used to look at living things


Specimen has to be chemically fixed i.e. dehydrated

Scanning electron microscopes SEM

Max mag approx 500 000x

Best for looking at surfaces of objects

Able to see objects in 3D

Scanning electron microscopes SEM cons

Resolution often not as high as the transmission electron microscope

Electrons do not pass through the specimen


Great skill/training to use

Staining samples for use in light microscopy

A lot of biological material inside a cell isn't coloured, so staining helps distinguish different features. Chemicals bind to other chemicals on, or in the specimen or specific structures.

Colouring in electron microscopy

Starts off black ands white, colour is added by specialised computer programs afterwards

Equation for image size

Image size= Actual size x Magnification

Structures of eukaryotic cells (14)

Nucleus, Nucleolus , nuclear envelope, rough and smooth endoplasmic reticulum, Golgi apparatus, ribosomes, mitochondria, lysosomes, chloroplasts, plasma membrane, centrioles, undulipodia and cilia.

Function of Nucleus

Stores all of the cells genetic material in the form of DNA, which contains the instructions for protein synthesis

Function of Nucleolus

Makes ribosomes and RNA which passes into the cytoplasm and are used in protein synthesis.

Function of Nuclear envelope

A double membrane with nuclear pores

Function of rough endoplasmic reticulum (RER)

Transports proteins made by the attached ribosomes

Function of smooth endoplasmic reticulum (SER)

Involved in making lipids

Function of Golgi apparatus

Modifies proteins received from the RER and then packages them into vesicles so they can be transported

Function of ribosomes

Site of protein synthesis

Function of mitochondria

Where ATP is made

Function of Lysosomes

Contain digestive enzymes that are used to break down material

Function of Chloroplasts

Site of photosynthesis in plant cells

Function of Plasma membrane

Controls the entry and exit of substances into and out of the cell.

Function of Centrioles

Form the spindle which moves chromosomes during cell division

Function of undulipodia and cilia

Move by ATP, e.g wave mucus along or make sperm swim

Making and secreting a protein

1. A gene with instructions encoded is copied onto a piece of mRNA.

2. mRNA leaves nucleus through nuclear pore

3. mRNA attaches to a ribosome, reads instructions to assemble the protein

5. Molecules pinched off in vesicles and travel to to Golgi apparatus

6. Vesicle fuses with G.A, that processes and packages the molecules ready for release

7. Pinched off in vesicles from the G.A travel to the plasma membrane

8. Vesicle fuses with it P.M opens and releases molecule outside

Cytoskeleton providing-

1. mechanical strength

2. aiding transport with cells

3. enabling cell movement

Due to protein fibres that keep the cells shape by giving an internal framework-

microfilaments and microtubes

Functions of microfilaments and microtubes

supporting organelles

strengthening the cell and maintaining cell shape

transporting materials within the cell (e.g. spindle during mitosis)

cell movement (cilia and flagella)

Cells prokaryotic and eukaryotic both have

plasma memebrane


ribosomes for assembling amino acids into proteins


Prokaryotic differences from eukaryotic

Do not have a nucleus

No membrane bound organelles

Cell wall made of peptidoglycan not cellulose

Smaller ribosomes

Naked DNA as a loop floating free in cytoplasm

Small loops of DNA called Plasmids

Prokaryotic cell division

Binary fission- before they divide their DNA is copied so that each new cell receives the large loop of DNA and any smaller plasmids

Structure and ultrastructure of plant cells

Cell wall thats outside the cell surface membrane and made of cellulose, its strong and is kept rigid by the pressure of the fluid inside the cell. The vacuole makes the cell stable and turgid which supports the whole cell.

Cell cycle- M phase

Checkpoint chemical triggers condensation of chromatin

Halfway through metaphase ensures the cell is ready to complete mitosis

Cell growth stops

Pro, meta, ana, tele and cytokineses occurs

Cell cycle- G0 phase

Testing phase triggered early during G1

Cells may undergo apoptosis (programmed cell death) differentiation (changes type of cell) or senescence (makes cells divide)

Some cells (neurons) remain in this phase for a very long time or indefinitely

Cell cycle- G1 phase

Checkpoint- ensures that the cell can enter S phase and begin DNA synthesis

Transcription of genes to make RNA occurs

Organelles duplicate

Cell cycle- S phase

All DNA molecules are replicated

Housekeeping genes duplicated

Once cells enter its committed to finishing the cycle

DNA replicated

The phase is rapid as DNA pairs susceptible to mutagenic agents reducing mutations

Cell cycle- Cytokine

Any number of substances which are secreted by certain cells of the immune system and have an effect on the other cells

Pre Mitosis, interphase

DNA prepares to divide, and replicates

Mitosis, prophase

Chromosomes supercoil & become visible under a Light microscope

The nuclear envelope breaks down

Centriole divide in two and move to opposite ends of the cell to form a spindle

Mitosis, metaphase

Chromosomes line up along the middle of the cell

They attach to the spindle thread by their centromere

Mitosis, anaphase

Replicated sister chromotids are separated yen the centromere splits

Spindle fibres shorten, pulling the chromotids apart

Mitosis, telophase

Separated sister chromotids reach the poles of the cells

A new nuclear envelope forms around each set

Spindle breaks down

Chromosomes uncoil so they are no longer visible under a light microscope

Cytokinesis, post mitosis

The whole cell splits down to two new cells, each one identical to each other and to the parent cell

Meiosis (first division) prophase

Chromosomes condense then arrange themselves Ito homologous pairs and crossing over occurs

Like mitosis- centrioles move opposite end of cell spindle fibres forms

Nuclear envelope breaks down

Meiosis (first division) Metaphase

Homologous pairs line up at centre of cell

Attach to the spindle fibres by their centromeres

Meiosis (first division) Anaphase

Spindle contracts, separating homologous pairs

One chromosome goes to each end of the cell

Meiosis (first division) Telophase

A nuclear envelope forms around each group of chromosomes

Meiosis cytokinesis

Division of cytoplasm, occurs and two haploid daughter cells are produced

Meiosis (second division)

At the end of meiosis 1= two haploid daughter cells

The two daughter cells undergo that stages again, PMATC again

Meiosis (second division) anaphase

Sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosome. 4 genetically different- haploid daughter calls are made (the gamete)

Chromatids cross over in prophase 1

Homologous pairs of chromosomes pair up, bits of chromatids swap over.

Chromatids still contain the same gene but have a different combination of alleles

How meiosis produces genetic variation

Crossing over during P1shuffles alleles

Independent assortment of chromosomes in A1leads to chromosomes line up randomly

Haploid gametes are produced that undergo random fusion with gametes

erythrocytes (red blood cells)

biconclave disc shape to maximise surface area

no nucleus = more room for haemoglobin


Flexible shape to engulf foregoing particles or pathogens

Many lysosomes contain digestive enzymes to break down the engulfed particles

Epithelial cells

Some have cilia to move particles

They are flattened in shape

Sperm cells (spermatozoa)

Many mitochondria, sperm head contain enzymes

Undulipodium to move, small, long and thin

Nucleus contains half chromosomes

palisade cells

contains chloroplasts to absorb light

thin walls so that CO2 can diffuse in

Root hair cells

Hair like projections to increase surface area to absorb water and minerals from the soil

Guard cells

thin outer wall, thick inner wall

in light they absorb water to become turgid and allow gaseous exchange


group of similar cells that perform a particular function


a collection of tissue that work together to form a specific overall function

organ system

a number of organs working together to form a life function

Ciliated epithelial tissue

Column shaped, exposed surface covered with cilia

Move in synchronised waves, e.g. waft mucus/eggs

Found on saurface of tubes

Cooperation between cells example

Movement: due to muscular and skeletal system, only if the nervous system 'instructs'.

It uses energy so requires supply of nutrients and oxygen from the circulatory system

Receiving chemicals from digestive and ventilation systems


Hyaline cartilage- forms the embyonic skeletion

Fibrous cartilage- occurs in discs between vertebrae

Elastic cartilage makes up the outer ear and the epiglottis

Muscle tissue

Vascularised (many blood vessels)

Elongated & contain myofilaments made of protein

Types of muscle

Skeletal- connective tissue sheets

Cardiac- walls of the heart

Smooth- walls of intestine, blood vessels, propels along these tracts (passages)

Epidermial Tissue

Flatterned cells, form protective covering over leaves, stem and rools

Some have walls impregnated with a waxy substances, forming a cuticle

Vascular Tissue

Tissue concerned with transport

Xylem & Phloem both present in vascular bundles

How Xylem derives from meristem (cambuim cells differentiate into xylem vessels)

Lignin (woody substances) deposited in their cell walls- reinforce, waterproof them but also kills the cell

Ends of cells break down, Xylem forms continuous columns with wide lumens to carry water and dissolved minerals

How phloem derives from meristem (cambium cells differentiate into phloem sieve tubes or companion cells)

Sieve tubes loose most of their organelles and sieveplates develop betweeen them

Companion cells retain their organelles and continue metabolic function to provide ATP for active loading of sugar into sieve tubes

Stem cells

Undifferenated cells able to express all of its genes and divide by mitosis

Sources of stem cells

Early embryo- when zygote begins to divide

Umbilical cord blood

Adult stem cells- bone marrow

Bone marrow transplants

Treats dieases of blood (sickle cell anamia & leukaemia) and immune system

Stem cells, development in biology

Enables a better understanding of how multicellular organism develop cell functions & what goes wrong when diseased

Why plants need a transport system

All living things need to take substances and return waste to their environment

Examples parts of the plant can that can do one thing but not another

Roots can obtain water but not sugars

Leaves can produce sugars but cannot obtain water from the air

Xylem and phloem tissue in Roots

Xylem is arranged in an X shape, phloem found between the arm of the xylem

Xylem and phloem tissue in Stem

Vascular bundles found around the outside of the stem in a ring shape

Xylem on the inside, phloem on the outside separated by a layer of cambium- meristem cells

Xylem and phloem tissue in Leaves

Xylem on top, phloem in the 'veins' of a leaf

Xylem function and structure

Transports water and mineral ions from the roots up to the leaves- vessels do this

Fibers help support the plant

Living parenchyma cells which act as packing tissues to separate and support the vessels

Xylem Vessels

Long thick walls impregnated by waterproof lignin- prevents collapsing, creates patterns making the stem or branch flexble

Vessels always stay open

Lignification is not complete= pits or bordered pits- allow water to leave & pass into living parts of the plant

Sieve tube elements

Little cytoplasm

No nucleus

Form a tube - sugars are transported

Sieve plates- cross walls that are perforated

Thin walls

Companion cells

Found between sieve tubes

Cytoplasm, nucleus, mitochondria

ATP loads sucrose into the phloem

Plasmodesmata between companion cells allows flow of minerals between the cells


Gaps in the cell wall containing cytoplasm that connect two cells

Apoplast pathway

Water passes through spaces in cell walls

By mass flow

Dissolved mineral ion & salts carried with water

Symplast pathway

Water passes through plasma membrane

Can pass through plasmodesmatas

Vacuolar pathway

Water passes through plasma membrane and vacuoles

Water potential

The tendency of water molecules to move from one place to another


The loss of water vapour from the aerial parts of a plant due to evaporation

Transpiration a consequence of gaseous exchange- how plants reduce water loss

Stomata opens- water can be lost to reduce this:

Waxy cuticle- prevents water through epidermis

Stomata closes at night

Deciduous plants loose leaves in winter- conserve the water that they have got

Factors that affect transpiration rate

Number of leaves

Number-size-position of stomata

Presence of cuticle



Relative humidity

Air movement

Water available

How a potometer is used to estimate transpiration Pt 1

Cut healthy shoot underwater to stop air entering xylem

Cutting shoot at a slant to increase surface area

Ensure apparatus is full of water and that there is only the desired air bubble

Insert shoot into apparatus underwater

How a potometer is used to estimate transpiration Pt 2

Remove potometer form water and ensure it is airtight around the shoot

Dry leaves and Keep conditions constant to allow shoot to acclimatize (adjust)

Shut screw fixed and record position of air bubble

Start timing and measure distance moved per unit of time

The movement of water between plant cells

Water passes from cell with higher water potential (less negative)

To the cell, with the lower water potential (more negative)

The movement of water between plant cells and their environment

Water moves down the water gradient

If water potential inside the cell is greater than the water potential outside the cell

Water moves out of the cell by osmosis

Vice versa

The pathway water is transported from the root cortex to the air surrounding the leaves Pt 1

Water enters the root hair cells by osmosis

At the same time, minerals are actively pumped from the root cortex into the xylem

Consequentially water moves from root hair cell along symplast pathway to follow the xylem

The pathway water is transported from the root cortex to the air surrounding the leaves Pt 2

Casparian strip blocks the apoplast pathway between the cortex and the xylem

Water must join the symplast pathway to reach the xylem

When water reaches the top of the xylem it enters the leaves

Leaves the leaves through the stomata

How Adhesion transports water from the root cortex to the air surrounding the leaves

Water molecules form hydrogen bonds with the walls of the xylem

As the xylem vessels are narrow H bonds can pull water up the sides of the vessel

How cohesion and the transpiration stream transports water from the root cortex to the air surrounding the leaves

Water molecules attract to each other due to forces of cohesion

The forces are strong enough t hold the molecules together in a long chain

As molecules are lost from the top the whole column is pulled up ad one chain

This is called the transpiration stream

How the if some xerophytes are adapted to reduce water loss by transpiration

Smaller leaves less surafce area

Densely packed spongy mesophyll

Thicker waxy cuticle

Closing stomata, stomata in pits

Hairs on surface of leave trap layer of air reduce diffusion of water out of stomata


Plants that live in water

Large air spaces in the leaf

Stomata are on the upper epidermis

Large air spaces in the stem helps with buoyancy and diffuse quickly


The transport of assimilates (substances that have become a part of the plant)throughout a plant

Translocation between sources (where the sugars come from eg leaves) and sinks (where they go eg roots)

Sugars made in leaves and transported to roots

in early spring leaves need energy to grow so sugars are transported from the roots (now the source) to the leaves (now the sink)

Transport in the phloem involving active loading at the source and removal at the sink Pt 1

ATP used by companion cells to actively transport proteins out of their cytoplasm and into the surrounding tissue

This sets up a diffusion gradient and the hydrogen inn diffuse back into the cells

Done through cotransport proteins which enable H ions to bring sucrose back into the cell with them

Transport in the phloem involving active loading at the source and removal at the sink Pt 2

Concentration of sucrose molecules builds up, they diffuse into the sieve tube elements through the plasmodesmata

The entrance of sucrose into the sieve tube elements reduces the water potential

water follows by osmosis and increases the hydrostatic pressure at the source to lower hydrostatic pressure at the sink

Transport in the phloem involving active loading at the source and removal at the sink Pt 3

Sucrose moves via either diffusion or active transport from sieve tube to the surrounding cells

This increases the water potential in the sieve tube elements so water moves into surrounding cells by osmosis

this reduces the hydrostatic pressure at the sink

Role of membrane within cells and at the surface of cells

Separate cell contents and components from the outside environment

Cell recognition and signalling

Holding the components of some metabolic pathways in place

Regulating the transport of materials into or out cells

Phospholipids membranes

Have a hydrophobic head and fatty acid tail

Form a bi-layer

Fluid so components can move around freely

Permeable, small, non polar but impermeable to large molecules and ions

Cholesterol membranes

Mechanical Stability

Sit between fatty acid tails making the barrier more complete

Glycolipids membranes

Phospholipid molecules that have a carbohydrate part attached

Used for cell signalling, cell surface antigens and cell adhesion

Proteins Membranes

Channel proteins allow the movement of large molecules into and out of the cell as they can't travel directly through the membrane

Carrier proteins actively move substances across the membrane

Glycoproteins membranes

Phospholipid molecules with a protein attached with a chain of carbohydrate molecules

Temperatures effect on phospholipids

Increasing temp = more kinetic energy membrane becomes more permeable so increases the fluidity

Temperature effect on cholesterol

Increased temperature = cholesterol pulls phospholipids together as they are attached to the cholesterol

The molecules in the membrane are closer = the fluidity of the membrane decreases

Unsaturated tails affect of membranes

Tails are bent = more distance

Double carbon bonds

More distance = increased fluidity

Saturated tails affect of membranes

Tails are straight = narrower distance

Single bond

Less distance = decreased fluidity

Passive transport

Transport of molecules without using energy

Diffusion net movement from high conc to low conc down a conc gradient

Larger molecules travel through carrier proteins shape only allow one molecule through often gated

Carrier proteins shaped to fit a specific molecule, then change shape to allow it to the other side

Active transport

Movement of molecules or ions across membranes, using ATP to drive 'protein pumps' within the membrane


When large quantities of a material are brought into the cell using ATP


When large quantities of a material are moved out the cell using ATP

Osmosis in terms of water poteintal

The movement of eater molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane


The concentration of solutes is greater inside the cell than outside of it


The concentration of solutes is greater outside the cell than inside it

Hyper-tonic in Plants

Water moves out of cells by osmosis down a water potential gradient

Plant membrane pulls away from cell wall as water leaves the cell is plasmolysed

Hyper-tonic In animals

Water moves out of cells by osmosis down a water potential gradient

Animal cell shrinks and appears wrinkled it is crenated

Hypo-tonic in plants

Water moves in by osmosis down a water potential gradient

plant cell wall prevents bursting membrane pushes against wall the cell is turgid

Hypo-tonic in animals

Water moves in by osmosis down a water potential gradient

animal cell bursts open it is cytolysed

Water as a liquid

Water molecules constantly move around and continually make and break hydrogen bonds

Density of water

Ideal habitat for living thing

Ice is less dense than water

Water as a solvent

Metabolic processes in all organisms rely on chemicals being able to react together in a solution

Cohesion in water

Water molecules stick to each other creating surface tension at the water surface

Synthesis of dipeptides and polypeptides

The -OH from one amino acid and then the -H from the -COOH from the other are removed to make water and the C and the N join together via a peptide bond

Hydrolysis of dipeptides and polypeptides

A water molecule is used to break the peptide bond

The -H joins back to the N, and the -OH back to the C

Primary structure

Sequence of amino acids found in a protein molecule

Secondary structure

The coiling or folding due to the formation of hydrogen bonds synthesised

Main forms are the alpha-helix and the beta-pleated sheet

Tertiary structure

3-D structure, result of interactions between parts of the protein molecule such as

hydrogen bonding

disulfide bridges

ionic bonding

hydrophobic and hydrophilic interactions

Quaternary structure

Proteins made up of more than one polypeptide chain

e.g. Haemoglobin made up of 4 polypeptide chains

Structure and function of haemoglobin

Globular protein

Soluble in water

Wide range of amino acids constituents in primary structure

Contains a prosthetic group- haem

Wound into alpha-helix structures

Structure and function of collagen

Fibrous protein

Insoluble in water

35% of the molecule's primary structure is gycine

Does not have a prosthetic group

Much of the molecule consists of left handed helix structures

Structure of an alpha-glucose


Structural difference between alpha and beta glucose

In alpha the -OH on carbon 1 is below the plane of the ring

In beta it is above the chain of the ring

Formation of disaccharide

water is eliminated as the -OH from one glucose and the -H from an -OH from the other leaves

The remaining O joins to the C on the other glucose making a disaccharide

Breaking of a disaccharide

Water is used to break the glycosidic bond between the subunits

The -H returns to the O and the -OH returns to C4

In polysaccharides there are many glucose subunits joined together by 1,4 gycosidic bonds


Made up of alpha glucose

straight chain

tends to coil up

plant storage polysaccaride


Made up the beta glucose

in a chain, alternate glucose subunits are inverted

forms straight chains

The beta glycosidic bond can only be broken down by an enzyme which herbivores have

Form plant cell walls

Structure and function of glycogen

Mostly like amylase, as it has many 1,4 glycosidic bonds, but there are 9% 1-6 branches

As it is highly branched it can be brake down the glucose very quickly

The function in living organisms of glucose

Simplists sugar, used in respiration

The function in living organisms of amylose

Insoluble in water so does not affect the water potential of the cell


Glycerol plus three fatty acids

The function in living organisms compact energy store insoluble in water doesn't affect cell water potential

Test for presence for protein (biuret test)

If present, turns from bale blue to lilac

Test for presence for reducing sugars (Benedict's test)

Add Benedict's, heat to 80 degrees

from blue to orange-red

Test for presence for non-reducing sugars

(Benedict's test)

If reducing sugar test is negative, boil with hydrochloric aid, cool and neutralise with sodium hydrocarbonate, repeat benedict's test

Test for presence for starch (iodine solution)

Turns from yellow to blue-black if starch prent

Test for presence for lipids (emulsion test)

Mix the ethanol

pour into water

if an emulsion forms a lipid is present

Nucleic acids DNA

DNA is a polynucleotide, usually double stranded

Nucleotides containing bases

A adenine

T thymine

C cytosine

G guanine


Is a polynucleotide, usually single stranded

made up of nucleotides containing bases

A adenine

U uracil

C cytosine

G guanine

Formation of DNA

AT pair up = (purines), CG pair up = (pyrimidines) Hydrogen bonds between complementary base

Strands are anti parallel chains and twist like a rope ladder to form a double helix

How DNA replicates

Double helix is untwisted

H bonds brake between bases, DNA 'unzips' by the eznyme helicase

Free DNA nucleotides are H bonded onto their exposed complementary bases

DNA polymerase catalyses the formation of covalent bonds between the phosphate of one molecule and the sugar of the next one,

continues all the way down till there are two identical strands, these are proof read by DNA polymerase to prevent mistakes

Protein synthesis

Gene exposed by splitting the hydrogen bonds that hold the double helix together

(mRNA) is complementary strand which is a copy of the DNA coding strand

mRNA peels away from the DNA and leaves nucleus from pores attaches to ribosome

tRNA bring amino acids to ribosome in correct order according to base sequence on mRNA

Amino acids joined by peptide bonds to give a protein with a specific tertiary structure

An enzyme

Are globular proteins

Specific tertiary structure

Catalyse metabolic reactions in living organisms



EX= outside the cell

IN= inside the cell

Active site

The area on an enzyme to which the substrate binds

lock and key hypothesis

The theory of enzyme action in which the enzyme active site is complementary to thesubstrate molecule, like a lock and key

induced-fit hypothesis

induced-fit hypothesis,The theory of enzyme action in which the enzyme molecule changes shape to fit thesubstrate molecule more closely as it binds to it

enzyme-substrate complex

The intermediary formed when a substrate molecule binds to an enzyme molecule

enzyme-product complex

The intermediate structure in which product molecules are bound to an enzyme molecule

lowering of activation energy

Enzymes reduce the activation enthalpy so the reaction can proceed at a much lowertemperature

Effect of pH on enzyme activity

Low pH = lots of H+ ions

H+ ion concentration can interfere with the hydrogen and ionic bondsholding the tertiary structure together.

The pH affects the charge of the amino acids at the active site, so the properties of theactive site change and the substrate can no longer bind

Effect of temperature on enzyme activity

Increasing temperature will increase the rate of reaction, as more collisions between enzymes and the substrate,

Puts strain on the inter-molecular bonds,and some of the weaker bonds (H bonds and ionic bonds) may break, after enough break the-

Tertiary structure will unravel and theenzyme will stop working, Becoming denatured

Effect of enzyme concentration on enzyme activity

Enzyme concentration increases, the rate of reaction increases

As more active sites are available

Until the substrate concentration becomes a limiting factorand the rate stops increasing

Effect of substrate concentration on enzyme activity

Increasing substrate concentration, the rate of reaction increases

As moresubstrate molecules to react.

At higher concentrations, all of the active sites become filled,so the rate of reaction remains the same

Competitive inhibitor molecules

Similar shape to that of the substrate molecule. They occupy theactive site, forming enzyme-inhibitor complexes.

Doesn't lead to theformation of products

Most don't bind permanently to the active site and leaves the enzyme molecule unaffected.

Non-competitive inhibitors

They attachto the enzyme at the allosteric site away from the active site and distorts the tertiary structure of the enzyme molecule changing the shape of the active site

The substrate no longer fits into theactive site so the enzyme-substrate complexes cannot form and the reaction ratedecreases.

Bind permanently to the enzyme molecule it's irreversible and are effectivelydenatured.


Ions that increase the rate of enzyme-controlled reactions.

Their presence allows enzyme substratecomplexes to form more easily.


Small, organic, non-protein molecules that bind for a short period of time to the active site.They may bind just before, or at the same time, as the substrate binds.

The role is often to carry chemical groups between enzymes so they link togetherenzyme-controlled reactions that need to take place in sequence.

Some coenzymes are permanent parts of the enzymes- prosthetic groups.

Metabolic poison that act as enzyme inhibitors

Potassium Cyanide acts as a non-competitive inhibitor of the enzyme cytochrome oxidase, which isinvolved in the oxidation of ATP.

When this is inhibited, aerobic respiration cannot occur, and sothe organism can only respire anaerobically, which leads to a build up of lactic acid, toxic to thecells.(i) state that some


microorganism that causes disease


Causes disease by damaging cells or releasing waste products or an toxins, toxic to the host

e.g. E-coli, Salmonella, TB


Animals- when in the skin it's hyphae forms a mycelium under the skin surface hyphae that are specialised & reproduce are sent out grow and release spores on the surface e.g. athlete's foot

Plants- vascular tissue is digested which causes decay from the hyphae releasing extracellular enzymes (cellulase) e.g. Black sigatoka (banana)



Transport in Animals: size of transport systems in multicellular animals

Once an animal has several layers of cells any oxygen or nutrients diffusing in form the outside willbe used up by the other layers of cells

The cells deeper in the body will not get any oxygen ornutrients.

level of activity in transport systems in multicellular animals

If an animal is very active then it will need a good supply of nutrients and oxygen to supply theenergy for movement.

surface area:volume ratio of transport systems in multicellular animals

It needs a range of tissues and structural support to givethe body strength.

Their volume increases as the body gets thicker, but the surface area does notincrease as much.

SA:V ratio of a large animal is relatively small. Largeranimals do not have a large enough surface area to supply all of the oxygen and nutrients that theyneed

single circulatory system

A circulation in which the blood flows through the heart once during each circulation of the bodye.g. fish

double circulatory system

A circulation in which the blood flows through the heart twice during each complete circulation ofthe body e.g. mammals

Open circulatory system

The blood is not always in vesselse.g. insects

Closed circulatory system

The blood is always in vesselse.g. fish

External structure of the mammalian heart


Internal structure of the mammalian heart