AQA Biology A-Level Paper 2 Test With Verified Answers Graded A
describe and explain the steps in the light dependent
reaction of photosynthesis - -1. photoionisation: light
reaches chlorophyll in PSII, which is absorbed by an describe krebs cycle in respiration. give net formation. -
electron, which becomes excited and moves to a higher -1. acetyl co-enzyme A combines with 4 carbon
energy level. molecule (oxaloacetate) to form 6 carbon citric acid.
2. the electron passes to a carrier protein in the thylakoid 2. CO2 is lost (decarboxylation), molecule is oxidised by
membrane, and is passed down a series of carrier NAD and ATP is produce. this forms 5 carbon compound.
molecules called an electron transfer chain. 3. it is oxidised by 2NADH and FAD, and is
3. as the electron moves down, energy is lost from the decarboxylated.
electron and is released as ATP. 4. this forms 4 carbon molecule again.
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 describe oxidative phosphorylation in respiration. - -
energy and boosts another electron to a higher energy 1. reduced coenzyme passes its H to a carrier protein in
level (excitation). the ETC. this splits into a proton and electron.
6. this electron also goes down an electron transport 2. the protons pass through the space between inner and
chain. outer mitochondrial membrane.
7. this reaches the final electron acceptor which is a 3. electrons pass through proteins on ETC.
proton. they combine to form H and reduce NADP to 4. protons return back via ATP synthase in the membrane,
NADPH. 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.
describe and explain the steps in the light independent
reaction pf photosynthesis. - -1. CO2 diffuses into
stroma and combines with ribulose bisphosphate (RuBP)
using the enzyme rubisco. define biomass - -the total mass of organisms in a
2. this forms an unstable 6 carbon molecule, which splits given area
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. what is the 'gross primary production' - -the
5. TP can also be reformed into RuBP using ATP. chemical energy stored in a plants biomass
describe glycolysis in respiration. give net formation. -
what is the 'net primary production' - -the chemical
-1. glucose is converted into phosphorylated energy stores in a plants biomass after respiratory losses
glucose by 2ATP. this makes it very reactive, so it splits have been considered. this energy is available to
into 2 triose phosphate (TP). consumers.
2. 2TP is then oxidised by 2NAD and 4 ATP is formed to
form pyruvate.
3. NET: 2ATP, 2Pyruvate, 2NADH, 2H+
how can you calculate the net primary production? -
-NPP = GPP - R
describe links reaction in respiration. give net formation. -
-1. pyruvate diffuses into the matrix of mitochondria.
2. pyruvate is oxidised by NAD. CO2 is lost. this forms why is converting sunlight energy into biomass in
acetate. producers inefficient? - -some light isn't the correct
3. acetate and co-enzyme A combine to form acetyl co-
wavelength to be absorbed
enzyme A.
some light doesnt hit chloroplast
4. NET: CO2, reduced NAD, acetyl co-enzyme A
some light is converted into heat energy
, AQA Biology A-Level Paper 2 Test With Verified Answers Graded A
some light energy is reflected
what is negative feedback? - -this is when the
change produced by the system leads to a change in the
describe the nitrogen cycle. - -fixation: stimulus detected by the receptor, turning the system off.
atmospheric nitrogen can be fixed by rhizbium bacteria.
if struck by lightning, it becomes reactive and combines
with oxygen to form NO.
what is positive feedback? - -this is when a deviation
ammonification: from the optimum causes changes that result in an even
saprobionts feed on organic matter and release ammonia, greater deviation from the norm
which then forms ammonium ions in the soil.
e.g. in neurones, a stimulus leads to an influx of Na+,
nitrification: which increases the membrane permeability to allow
nitrifying bacteria convert ammonium ions into nitrite ions further NA+ to enter.
and then to nirate ions.
denitrification:
anaerobic denitrifying bacteria convert soil nitrates into describe the second messenger model. - -1.
gaseous nitrogen. Adrenaline binds to transmembrane protein receptor in the
cell surface membrane of a liver cell.
2. the binding of adrenaline causes the protein to change
shape on the inside of the membrane.
homeostasis - -the maintenance of an internal 3. the change in tertiary structure activates adenyl cyclase,
environment within restricted limits in organisms. all cells which converts ATP to cAMP.
are in an environment that meets their requirements and 4. cAMP binds to kinase, changes structure and activates
allows them to function normally despite external it.
changes. 5. this catalyses the conversion of glycogen to glucose,
which moves out of the liver cell and into the blood by
facilitated diffusion.
why is homeostasis important? - -1. the enzymes
that control biochemical reactions in cells are sensitive to
change e.g. in pH or temperature, which can cause them glycogenesis - -conversion of glucose to glycogen.
to denature. homeostasis allows enzyme controlled this is when glucose levels are abnormally high.
reactions to take place at a suitable rate.
2. homeostasis allows a constant blood glucose
concentration to ensure a constant water potential, so glycogenolysis - -breakdown of glycogen to glucose.
cells don't shrink or burst. this is when glucose levels are abnormally low.
3. homeostasis allows organisms to be more independent
of external changes.
gluconeogenesis - -production of glucose from
sources other than carbohydrates, such as glycerol or fatty
acids. occurs when there's insufficient glycogen.
list the parts of control mechanisms in homeostasis. -
-1. optimum temperature
2. receptor- detects any deviation from the optimum
temperature how does insulin and beta cells in the pancreas affect
3. coordinator- info from receptor to effector glucose levels? - -1. the beta cells in the pancreas
4. effector- often a muscle/gland, brings about change to
detect a rise in the blood glucose concentration and
return the system to optimum level
respond by secreting insulin into blood.
5. feedback mechanism
2. insulin binds to glycoprotein receptors on cells.
describe and explain the steps in the light dependent
reaction of photosynthesis - -1. photoionisation: light
reaches chlorophyll in PSII, which is absorbed by an describe krebs cycle in respiration. give net formation. -
electron, which becomes excited and moves to a higher -1. acetyl co-enzyme A combines with 4 carbon
energy level. molecule (oxaloacetate) to form 6 carbon citric acid.
2. the electron passes to a carrier protein in the thylakoid 2. CO2 is lost (decarboxylation), molecule is oxidised by
membrane, and is passed down a series of carrier NAD and ATP is produce. this forms 5 carbon compound.
molecules called an electron transfer chain. 3. it is oxidised by 2NADH and FAD, and is
3. as the electron moves down, energy is lost from the decarboxylated.
electron and is released as ATP. 4. this forms 4 carbon molecule again.
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 describe oxidative phosphorylation in respiration. - -
energy and boosts another electron to a higher energy 1. reduced coenzyme passes its H to a carrier protein in
level (excitation). the ETC. this splits into a proton and electron.
6. this electron also goes down an electron transport 2. the protons pass through the space between inner and
chain. outer mitochondrial membrane.
7. this reaches the final electron acceptor which is a 3. electrons pass through proteins on ETC.
proton. they combine to form H and reduce NADP to 4. protons return back via ATP synthase in the membrane,
NADPH. 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.
describe and explain the steps in the light independent
reaction pf photosynthesis. - -1. CO2 diffuses into
stroma and combines with ribulose bisphosphate (RuBP)
using the enzyme rubisco. define biomass - -the total mass of organisms in a
2. this forms an unstable 6 carbon molecule, which splits given area
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. what is the 'gross primary production' - -the
5. TP can also be reformed into RuBP using ATP. chemical energy stored in a plants biomass
describe glycolysis in respiration. give net formation. -
what is the 'net primary production' - -the chemical
-1. glucose is converted into phosphorylated energy stores in a plants biomass after respiratory losses
glucose by 2ATP. this makes it very reactive, so it splits have been considered. this energy is available to
into 2 triose phosphate (TP). consumers.
2. 2TP is then oxidised by 2NAD and 4 ATP is formed to
form pyruvate.
3. NET: 2ATP, 2Pyruvate, 2NADH, 2H+
how can you calculate the net primary production? -
-NPP = GPP - R
describe links reaction in respiration. give net formation. -
-1. pyruvate diffuses into the matrix of mitochondria.
2. pyruvate is oxidised by NAD. CO2 is lost. this forms why is converting sunlight energy into biomass in
acetate. producers inefficient? - -some light isn't the correct
3. acetate and co-enzyme A combine to form acetyl co-
wavelength to be absorbed
enzyme A.
some light doesnt hit chloroplast
4. NET: CO2, reduced NAD, acetyl co-enzyme A
some light is converted into heat energy
, AQA Biology A-Level Paper 2 Test With Verified Answers Graded A
some light energy is reflected
what is negative feedback? - -this is when the
change produced by the system leads to a change in the
describe the nitrogen cycle. - -fixation: stimulus detected by the receptor, turning the system off.
atmospheric nitrogen can be fixed by rhizbium bacteria.
if struck by lightning, it becomes reactive and combines
with oxygen to form NO.
what is positive feedback? - -this is when a deviation
ammonification: from the optimum causes changes that result in an even
saprobionts feed on organic matter and release ammonia, greater deviation from the norm
which then forms ammonium ions in the soil.
e.g. in neurones, a stimulus leads to an influx of Na+,
nitrification: which increases the membrane permeability to allow
nitrifying bacteria convert ammonium ions into nitrite ions further NA+ to enter.
and then to nirate ions.
denitrification:
anaerobic denitrifying bacteria convert soil nitrates into describe the second messenger model. - -1.
gaseous nitrogen. Adrenaline binds to transmembrane protein receptor in the
cell surface membrane of a liver cell.
2. the binding of adrenaline causes the protein to change
shape on the inside of the membrane.
homeostasis - -the maintenance of an internal 3. the change in tertiary structure activates adenyl cyclase,
environment within restricted limits in organisms. all cells which converts ATP to cAMP.
are in an environment that meets their requirements and 4. cAMP binds to kinase, changes structure and activates
allows them to function normally despite external it.
changes. 5. this catalyses the conversion of glycogen to glucose,
which moves out of the liver cell and into the blood by
facilitated diffusion.
why is homeostasis important? - -1. the enzymes
that control biochemical reactions in cells are sensitive to
change e.g. in pH or temperature, which can cause them glycogenesis - -conversion of glucose to glycogen.
to denature. homeostasis allows enzyme controlled this is when glucose levels are abnormally high.
reactions to take place at a suitable rate.
2. homeostasis allows a constant blood glucose
concentration to ensure a constant water potential, so glycogenolysis - -breakdown of glycogen to glucose.
cells don't shrink or burst. this is when glucose levels are abnormally low.
3. homeostasis allows organisms to be more independent
of external changes.
gluconeogenesis - -production of glucose from
sources other than carbohydrates, such as glycerol or fatty
acids. occurs when there's insufficient glycogen.
list the parts of control mechanisms in homeostasis. -
-1. optimum temperature
2. receptor- detects any deviation from the optimum
temperature how does insulin and beta cells in the pancreas affect
3. coordinator- info from receptor to effector glucose levels? - -1. the beta cells in the pancreas
4. effector- often a muscle/gland, brings about change to
detect a rise in the blood glucose concentration and
return the system to optimum level
respond by secreting insulin into blood.
5. feedback mechanism
2. insulin binds to glycoprotein receptors on cells.
