AQA AS BIOLOGY PAPER 2 VIEW AHEAD
EXAM WITH TESTED QUESTIONS AND
ANSWERS 2026
‣ 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
EXAM WITH TESTED QUESTIONS AND
ANSWERS 2026
‣ 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
