AQA biology a-level paper 2
Study online at https://quizlet.com/_4z9voc
1. describe and ex- 1. photoionisation: light reaches chlorophyll in PSII, which
plain the steps in is absorbed by an electron, which becomes excited and
the light depen- moves to a higher energy level.
dent reaction of 2. the electron passes to a carrier protein in the thylakoid
photosynthesis membrane, and is passed down a series of carrier mole-
cules 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 en-
ergy 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.
2. describe and ex- 1. CO2 diffuses into stroma and combines with ribulose
plain the steps bisphosphate (RuBP) using the enzyme rubisco.
in the light in- 2. this forms an unstable 6 carbon molecule, which splits
dependent reac- into 2 3 carbon molecules, glyercate-3-phosphate (G3P)
tion pf photosyn- .
thesis. 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.
3. describe glycoly- 1. glucose is converted into phosphorylated glucose by
sis in respiration. 2ATP. this makes it very reactive, so it splits into 2 triose
give net forma- phosphate (TP).
tion. 2. 2TP is then oxidised by 2NAD and 4 ATP is formed to
form pyruvate.
3. NET: 2ATP, 2Pyruvate, 2NADH, 2H+
4. describe links re- 1. pyruvate diffuses into the matrix of mitochondria.
action in respira- 2. pyruvate is oxidised by NAD. CO2 is lost. this forms
, AQA biology a-level paper 2
Study online at https://quizlet.com/_4z9voc
tion. give net for- acetate.
mation. 3. acetate and co-enzyme A combine to form acetyl
co-enzyme A.
4. NET: CO2, reduced NAD, acetyl co-enzyme A
5. describe krebs 1. acetyl co-enzyme A combines with 4 carbon molecule
cycle in respira- (oxaloacetate) to form 6 carbon citric acid.
tion. give net for- 2. CO2 is lost (decarboxylation), molecule is oxidised by
mation. NAD and ATP is produce. this forms 5 carbon compound.
3. it is oxidised by 2NADH and FAD, and is decarboxylat-
ed.
4. this forms 4 carbon molecule again.
6. describe oxida- 1. reduced coenzyme passes its H to a carrier protein in
tive phosphory- the ETC. this splits into a proton and electron.
lation in respira- 2. the protons pass through the space between inner and
tion. 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.
7. define biomass the total mass of organisms in a given area
8. what is the the chemical energy stored in a plants biomass
'gross primary
production'
9. what is the 'net the chemical energy stores in a plants biomass after
primary produc- respiratory losses have been considered. this energy is
tion' available to consumers.
10. how can you cal- NPP = GPP - R
culate the net
primary produc-
tion?
11.
, AQA biology a-level paper 2
Study online at https://quizlet.com/_4z9voc
why is convert- some light isn't the correct wavelength to be absorbed
ing sunlight en- some light doesnt hit chloroplast
ergy into bio- some light is converted into heat energy
mass in produc- some light energy is reflected
ers inefficient?
12. describe the ni- fixation:
trogen cycle. 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 ammo-
nia, which then forms ammonium ions in the soil.
nitrification:
nitrifying bacteria convert ammonium ions into nitrite ions
and then to nirate ions.
denitrification:
anaerobic denitrifying bacteria convert soil nitrates into
gaseous nitrogen.
13. homeostasis the maintenance of an internal environment within re-
stricted limits in organisms. all cells are in an environment
that meets their requirements and allows them to function
normally despite external changes.
14. why is home- 1. the enzymes that control biochemical reactions in cells
ostasis impor- are sensitive to change e.g. in pH or temperature, which
tant? can cause them to denature. homeostasis allows enzyme
controlled reactions to take place at a suitable rate.
2. homeostasis allows a constant blood glucose concen-
tration to ensure a constant water potential, so cells don't
shrink or burst.
3. homeostasis allows organisms to be more independent
of external changes.
Study online at https://quizlet.com/_4z9voc
1. describe and ex- 1. photoionisation: light reaches chlorophyll in PSII, which
plain the steps in is absorbed by an electron, which becomes excited and
the light depen- moves to a higher energy level.
dent reaction of 2. the electron passes to a carrier protein in the thylakoid
photosynthesis membrane, and is passed down a series of carrier mole-
cules 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 en-
ergy 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.
2. describe and ex- 1. CO2 diffuses into stroma and combines with ribulose
plain the steps bisphosphate (RuBP) using the enzyme rubisco.
in the light in- 2. this forms an unstable 6 carbon molecule, which splits
dependent reac- into 2 3 carbon molecules, glyercate-3-phosphate (G3P)
tion pf photosyn- .
thesis. 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.
3. describe glycoly- 1. glucose is converted into phosphorylated glucose by
sis in respiration. 2ATP. this makes it very reactive, so it splits into 2 triose
give net forma- phosphate (TP).
tion. 2. 2TP is then oxidised by 2NAD and 4 ATP is formed to
form pyruvate.
3. NET: 2ATP, 2Pyruvate, 2NADH, 2H+
4. describe links re- 1. pyruvate diffuses into the matrix of mitochondria.
action in respira- 2. pyruvate is oxidised by NAD. CO2 is lost. this forms
, AQA biology a-level paper 2
Study online at https://quizlet.com/_4z9voc
tion. give net for- acetate.
mation. 3. acetate and co-enzyme A combine to form acetyl
co-enzyme A.
4. NET: CO2, reduced NAD, acetyl co-enzyme A
5. describe krebs 1. acetyl co-enzyme A combines with 4 carbon molecule
cycle in respira- (oxaloacetate) to form 6 carbon citric acid.
tion. give net for- 2. CO2 is lost (decarboxylation), molecule is oxidised by
mation. NAD and ATP is produce. this forms 5 carbon compound.
3. it is oxidised by 2NADH and FAD, and is decarboxylat-
ed.
4. this forms 4 carbon molecule again.
6. describe oxida- 1. reduced coenzyme passes its H to a carrier protein in
tive phosphory- the ETC. this splits into a proton and electron.
lation in respira- 2. the protons pass through the space between inner and
tion. 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.
7. define biomass the total mass of organisms in a given area
8. what is the the chemical energy stored in a plants biomass
'gross primary
production'
9. what is the 'net the chemical energy stores in a plants biomass after
primary produc- respiratory losses have been considered. this energy is
tion' available to consumers.
10. how can you cal- NPP = GPP - R
culate the net
primary produc-
tion?
11.
, AQA biology a-level paper 2
Study online at https://quizlet.com/_4z9voc
why is convert- some light isn't the correct wavelength to be absorbed
ing sunlight en- some light doesnt hit chloroplast
ergy into bio- some light is converted into heat energy
mass in produc- some light energy is reflected
ers inefficient?
12. describe the ni- fixation:
trogen cycle. 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 ammo-
nia, which then forms ammonium ions in the soil.
nitrification:
nitrifying bacteria convert ammonium ions into nitrite ions
and then to nirate ions.
denitrification:
anaerobic denitrifying bacteria convert soil nitrates into
gaseous nitrogen.
13. homeostasis the maintenance of an internal environment within re-
stricted limits in organisms. all cells are in an environment
that meets their requirements and allows them to function
normally despite external changes.
14. why is home- 1. the enzymes that control biochemical reactions in cells
ostasis impor- are sensitive to change e.g. in pH or temperature, which
tant? can cause them to denature. homeostasis allows enzyme
controlled reactions to take place at a suitable rate.
2. homeostasis allows a constant blood glucose concen-
tration to ensure a constant water potential, so cells don't
shrink or burst.
3. homeostasis allows organisms to be more independent
of external changes.
