Biology-Year 13

phosphorylation

occurs in the chlorophyll during photosynthesis where ATP is reformed from ADP+Pi

oxidative phosphorylation

occurs in the mitochondria during the electron transport chain (part of respiration)

substrate level phosphorylation

when phosphate groups are transferred from donor molecules to ADP

thylakoid membranes

in the chloroplast, contains chlorophyll A and B and carotene pigments, these are attached to proteins and called a photosystem

Grana

stacks of thylakoid sacks

stroma

a gel like substance surrounding the grana, enclosed in the inner membrane, contains enzymes and sugars

Chloroplast DNA

found in the stroma, often circular

lamellae (linky linky lamellae ladder)

sheet like structure joining the grana

photosynthetic pigments

chlorophyll A and B (green leaves), accessory pigments such as carotene (orange leaves) and anthocyanins (red leaves)

chlorophyll pigment

tail projects into the thylakoid membrane and acts as an anchor, different chlorophylls have different side chains and that’s what modifies its absorption spectra, chlorophyll A is the most abundant.

the light compensation point

2 point in the day where there is a zero net CO2 exchange, this is because the level of light intensity where the rates of photosynthesis and respiration are the same

Gibberelins

cause stem elongation, trigger mobilisation of food stores in seed germination, stimulate pollen tube growth in fertilisation.

auxin

control cell elongation, prevent leaf loss (abscission), maintain apical dominance, involved in tropisms, stimulate release of ethene and involved in fruit ripening

hormone

molecules that act as chemical messengers.

ethene

promotes fruit ripening, promotes leaf fall (abscission)

cytokines

promote cell division

abscisic acid-ABA

maintains seed dormancy, stimulates cold protective responses like antifreeze production and stimulates stomatal closing.

stimulus

a change in energy in the environement

sensory receptor

detects a stimulus at the end of some neurones. They act as transducers and convert energy from a stimulus into electrical energy. This generates an action potential.

voluntary response

stimulus-sensory receptor-CNS-motor neurone-effector

effector

a muscle or a gland which produces a response to the stimulus

synapse

a gap between neurones, when the action potential reaches the end of neurone1 the neurotransmitter diffuses across this gap to neurone 2 and the action potential is generated across neuron 2.

dendrites

transmits action potential towards the cell body, usually attached to the cell body apart from in a sensory neurone

axon

take the action potential away from the cell body with a terminal at the end (effector end)

Schwann cell

wrap around the axon and many make up the myeline (lipid) sheath (cover). It acts as an insulator for the action potential to speed up neurotransmission.

cell body of a neurone

nucleus lots of mitochondria as energy from respiration is used in active transport of ions. Lots of RER/ribosomes to synthesise neurotransmitters

resting potential

no action potential is being transmitted, the inside of the neurone is negatively charged and positive on the outside

depolarisation

charge in the neuron is positive and negative on the outside (reversal of charge) this generates action potential

saltatory conduction

Schwann cells prevent depolarisation on that part of the axon, only on the node of Ranvier, action potential is forced to jump from the cell body to the node of Ranvier, this keep happening unit it reaches the axon terminal. Faster because only small regions need to be depolarised.

hyperpolarisation

After repolarisation occurs, too many potassium ions leave the axon so it is more negatively charged than usual at resting potential. 

refractory period

another action potential cannot be generated as a larger influx of sodium ions would be needed to cause depolarisations, this means action potentials are unidirectional and discrete (do not overlap)

synergism

different plant hormones working together and giving a greater response than they would on their own. for example, auxin and cytokines

Antagonism

If the substances have opposite effects then the balance between them will determine the response of the plant.

photoperiodism

plant response to lack of daylight, many different responses are triggered by this e.g breaking bud dormancy.

Abscission

plant responds to falling auxin levels by producing ethene causing leaf loss, ethene initiates enzyme production which digest the cell wall on the outer layer of the abscission layer and vascular bundles are sealed off.

antifreeze production in plants

cytoplasm and vacuole contain solutes which lower the freeziging point. Some plants produce produce saccharides or proteins which act as antifreeze

stomatal control

way to respond to heat and water availability, plant hormone ABA causes stomatal closure

Physical defences against herbivory

thorns, barbs, spikes, inedible tissue or hairy leaves.

tannins

have a very bitter taste, toxic to insects binding to the digestive enzymes

alkaloids

bitter tasting nitrogenous compounds, many acting as drugs affecting the metabolism of animals and can sometimes be poisonous including caffeine, nicotine, morphine and cocaine

pheromones

chemical made by the plant and is released to act between plants and other organisms like insects, they use them to defend themselves

leaf folding in response to touch

drastic loss of water makes the leaf fold to scare of herbivores and shake off insects.

commercial use of plant hormones

control of ripening-ethene

weedkillers-synthetic auxins

hormone rooting powders- auxin

uses of triose phosphate 

carbohydrates-TP is used to make glucose, highly reactive so a fructose is added.

lipids- made of glycerol and fatty acids, the glycerol is made of TP and fatty acids are made from GP in the glycolysis pathway 

amino acids- GP and TP contain the C, H and O needed and N and S are obtained from the soil.

light intensity effect on photosynthesis

the rate of photosynthesis increases as light intensity increases until another factor limits it

CO2 concentration increases effect on photosynthesis

rate of photosynthesis increases until the CO2 diffusion gradient becomes constant. When it plateaus, there is not enough RUBP so another factor is limiting it.

temperature effect on photosynthesis

most light independent reactions (and some dependent) are enzyme controlled, if the temp is too low the enzyme work slower as less collisions with substrates so less enzyme-substrate complexes form, if the temp is too high enzymes become denatured.

glycolysis

the oxidation of glucose (6C) into pyruvate ( 2×3C), occurs in the cytoplasm and is anaerobic. 

glycolysis pt.1 phosphorylation of the sugar

a phosphate is added to glucose from an ATP this makes hexose phosphate. This is phosphorylated to make hexose biphosphate. This is split into 2 TP

glycolysis pt.2 oxidation of dehydrogenation

TP is oxidised . NAD collects this H to form 2 NADH. 4 ATP is produced, but 2 is used in stage 1, so net gain of 2.