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AQA biology a-level paper 2 June 2024 Exam Question and Answers
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AQA biology a-level paper 2 June 2024 Exam Question and Answers
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AQA biology a-level paper2 June 2024 Exam
Question and Answers
describe and explain the steps in the light dependent reaction of
photosynthesis - Answer>> 1. photoionisation: light reaches
chlorophyll in PSII, which is absorbed by an electron, which
becomes excited and moves to a higher energy level.
2. the electron passes to a carrier protein in the thylakoid
membrane, and is passed down a series of carrier molecules
called an electron transfer chain.
3. as the electron moves down, energy is lost from the electron
and is released as ATP.
4. the loss of electron from PSII is 'refilled' by an electron
produced by photolysis, which also produces hydrogen and
oxygen.
5. the lost electron reaches PSI, which absorbs light energy and
boosts another electron to a higher energy level (excitation).
6. this electron also goes down an electron transport chain.
7. this reaches the final electron acceptor which is a proton. they
combine to form H and reduce NADP to NADPH.
describe and explain the steps in the light independent reaction pf
photosynthesis. - Answer>> 1. CO2 diffuses into stroma and
combines with ribulose bisphosphate (RuBP) using the enzyme
rubisco.
2. this forms an unstable 6 carbon molecule, which splits into 2 3
carbon molecules, glyercate-3-phosphate (G3P) .
3. G3P is reduced by NADPH to triose-phosphate (TP), which is
aided by ATP for energy.
4. TP can be converted into useful organic substances.
,5. TP can also be reformed into RuBP using ATP.
describe glycolysis in respiration. give net formation. -
Answer>> 1. glucose is converted into phosphorylated glucose
by 2ATP. this makes it very reactive, so it splits into 2 triose
phosphate (TP).
2. 2TP is then oxidised by 2NAD and 4 ATP is formed to form
pyruvate.
3. NET: 2ATP, 2Pyruvate, 2NADH, 2H+
describe links reaction in respiration. give net formation. -
Answer>> 1. pyruvate diffuses into the matrix of mitochondria.
2. pyruvate is oxidised by NAD. CO2 is lost. this forms acetate.
3. acetate and co-enzyme A combine to form acetyl co-enzyme A.
4. NET: CO2, reduced NAD, acetyl co-enzyme A
describe krebs cycle in respiration. give net formation. -
Answer>> 1. acetyl co-enzyme A combines with 4 carbon
molecule (oxaloacetate) to form 6 carbon citric acid.
2. CO2 is lost (decarboxylation), molecule is oxidised by NAD and
ATP is produce. this forms 5 carbon compound.
3. it is oxidised by 2NADH and FAD, and is decarboxylated.
4. this forms 4 carbon molecule again.
describe oxidative phosphorylation in respiration. - Answer>> 1.
reduced coenzyme passes its H to a carrier protein in the ETC.
this splits into a proton and electron.
2. the protons pass through the space between inner and outer
mitochondrial membrane.
3. electrons pass through proteins on ETC.
4. protons return back via ATP synthase in the membrane,
producing ATP.
5. the protons and electrons recombine to form H, which
combines with O to form water.
, 6. oxygen is the last electron acceptor in the ETC.
define biomass - Answer>> the total mass of organisms in a
given area
what is the 'gross primary production' - Answer>> the chemical
energy stored in a plants biomass
what is the 'net primary production' - Answer>> the chemical
energy stores in a plants biomass after respiratory losses have
been considered. this energy is available to consumers.
how can you calculate the net primary production? - Answer>>
NPP = GPP - R
why is converting sunlight energy into biomass in producers
inefficient? - Answer>> some light isn't the correct wavelength
to be absorbed
some light doesnt hit chloroplast
some light is converted into heat energy
some light energy is reflected
describe the nitrogen cycle. - Answer>> fixation:
atmospheric nitrogen can be fixed by rhizbium bacteria.
if struck by lightning, it becomes reactive and combines with
oxygen to form NO.
ammonification:
saprobionts feed on organic matter and release ammonia, which
then forms ammonium ions in the soil.
nitrification:
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