Paper 2 recall Flashcards
Where are electron carries in photosynthesis located?
The thylakoid membrane
Where are protons pumped to and from in the chemiosmotic theory of photosynthesis?
They move from the stroma into the thylakoid intermembrane space
How are the electrons in chlorophyll replaced after photoionisation?
Photolysis of water splits to release electrons
What are all the products of the light dependent stage?
Oxygen, NADPH and ATP
What are some of the adaptations of chlorophyll for photosythesis?
Contain DNA and ribosomes to make proteins and enzymes, selectively permeable allows H+ gradient established, thylakoid membrane has large SA for chlorophyll, electron carriers and enzyme attachment and grana maximises light absorption
How is GP reduced to TP in photosynthesis?
Glycerate 3-phosphate is reduced to triose phosphate as NADPH is oxidised to NADP and energy is supplied from ATP
How is RuBP regenerated?
Most TP reforms Ribulose BiPhosphate using ATP
How is TP converted to pyruvate in glycolysis?
It is oxidised and NADH formed, each TP also synthesises two ATP per molecule so net gain 2 ATP for the whole of glycolysis
What happens in the link reaction?
The pyruvate is oxidised to acetate, CO2 is lost from the molecule and two hydrogens to form 1 NADH, acetate then combines with coenzyme A to form acetylcoenzyme A
What are the raw products for one Kreb cycle?
2 CO2, 3NADH, 1 FADH and one ATP
How are electrons released at the ETC of oxidative phosphorylation?
The Hydrogen atoms of NADH and FADH are released and they split to release electron which enter the carrier proteins and protons
How is the release of energy from electrons controlled?
As they move through the electron carriers, they move into lower energy levels so down an energy gradient, this causes gradual releases of energy that allow all the energy to be used
What are lipids and proteins converted to for use in respiration?
Glycerol becomes phosphorylates then becomes TP, fatty acids are converted to Acetyl Coenzyme A and proteins are converted to intermediates of the Krebs cycle
How is NAD regenerated in anaerobic respiration?
The pyruvate becomes reduced
What happens to lactate once oxygen becomes available again?
It is oxidised back to pyruvate which can then be further oxidised to release energy or converted into glycogen in the liver
What are saprobionts?
Organisms that break down the complex materials of dead organisms into simple structure that can be used by plants
What is biomass?
Total mass of living material in a specific area at a given time (mass of carbon easier measure due to water varying)
Why is so much of the suns energy NOT used to synthesise organic substances by plants?
90% of the sun energy reflected back by clouds and dust, not all wavelengths of light absorbed by plants, light may not fall on chlorophyll molecule and other factors such as CO2 may limit the rate of photosynthesis leading to 1-3% of the suns energy harnessed
What is the Gross Primary Production?
Total quantity of chemical energy store in plant biomass in a given area or volume in a given time
What is NPP used for?
Growth and reproduction
Why is energy transfer between trophic levels low?
Not all of the organism consumed, some parts not digested (faeces), energy lost in excretion (urine) and heat losses from respiration
How have nitrogen fertilisers reduced species diversity?
Soils favour the growth of grasses, nettles and other rapidly growing species, these out-compete many other species
What is IAA?
Indoleacetic acid (a plant growth factor)
How does IAA affect roots?
Inhibits cell elongation
What is the proposed explanation for IAA increasing plasticity of cell walls?
Acid growth hypothesis, active transport of H+ ions from the cytoplasm into spaces in the cell walls causing cell wall to become more plastic allowing the cell to elongate by expansion
What is the peripheral nervous system?
Pairs of nerves that originate from either the brain or the spinal cord
What are the features of a reflex?
Rapid, short lived, localised and involuntary
What does the coordinator neurone do?
Links the sensory neurone to the motor neurone in the spinal cord
How does the Pacinian Corpuscle act as a transducer?
Converts the change in the form of energy by the stimulus into nerve impulses that can be understood by the body
What are the features of rod cells?
Abundant, only see black and white, many connected to one bipolar cell, low light intensity, night vision, single impulse so low visual acuity, found at the peripheries
What are the features of cone cells?
Three different types (different sensitivities to wavelengths), own bipolar cell connected, only respond to high light intensity (iodopsin broke down), multiple impulses so good visual acuity, found only at the fovea
How does the heart beat?
SAN emits wave of electricity which causes atria to contract, this reaches AVN which emits another wave through Purkyne fibres in Bundle of His to cause ventricles to contract from the bottom upwards
What are the 6 features of mammalian motor neurones?
A cell body, dendrons, an axon, Schwann cells, myelin sheath and nodes of Ranvier
What are dendrons?
Extensions of the cell body which subdivide into smaller branched fibres called dendrites, that carry nerve impulses towards the cell body
What is an axon?
A single long fibre that carries nerve impulses away from the body cell
What are Schwann cells?
Surround the axon to protect it, and provide electrical insulation, they also carry out phagocytosis, they wrap aourn the axon many times to form the myelin sheath
How is a potential difference established (resting potential)?
Three sodium ions actively transported out and two potassium ions actively transported in by sodium potassium pump, sodium ions channels closed but potassium ion channels open
How does hyperpolarisation occur?
Outward diffusion of potassium ions causes temporary overshoot in electrical gradient, with the inside of the axon being more negative than usual
How does depolarisation of one region on an axon transfer to the next?
Sodium ion channels are voltage gated so when one are has an increase in voltage it causes adjacent sodium ion channels to open
What factors increase the speed of action potentials along an axon?
Presence of a myelin sheath, larger diameter (less leakage) and higher temperatures (until denaturation)
How do organisms perceive the different sizes of stimuli?
By the number of impulses passing in a given time and by having different neurones with different threshold values
What are the purposes of the refractory period?
Ensure the action potentials are propagated in one direction only, produces discrete impulses (separates action potentials) and limits the number of action potentials passing along one axon
How do inhibitory synapses operate?
Neurotransmitters bind to chloride ion protein channels, causing them to open so Cl- move into post-synaptic neurone, K+ channels also open so K+ moves out, this causes hyperpolarisation, meaning threshold potentials harder to reach
What are excitatory synapses?
Synapses that generate a new action potential
What are the processes of transmission across a cholinergic synapse?
Action potential arrives at synaptic knob and Ca2+ channels open for Ca2+ to move into knob, causing synaptic vesicles to fuse with the membrane and acetylcholine released into synaptic cleft, diffuse and bind to receptors on Na+ channels, allowing Na+ to diffuse in, generating a new action potential, acetylcholinesterase then breaks it down and it diffuses back to the pre-synaptic neurone, ATP reforms acetyl choline and is stored for future use
What are the different bands in muscles?
I band is lighter as it consists only of the thin actin and A bands are darker as this is where the thick and thin bands overlap
What is the Z line?
Marks the end of the sarcomere
How are slow twitch muscle fibres adapted to aerobic respiration?
A large store of myoglobin, a rich supply of blood vessels to deliver oxygen and glucose and numerous mitochondria to produce ATP