AQA biology a-level paper 2
Exam Questions and Answers
100% PASS
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
© 2026 Copyright. All Rights Reserved. This document is
protected by copyright law, Copyrighted By Katelyn Whitman
, 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
Exam Questions and Answers
100% PASS
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
© 2026 Copyright. All Rights Reserved. This document is
protected by copyright law, Copyrighted By Katelyn Whitman
, 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
