1.
glucose is broken down to pyruvate in the cytoplasm;
with a small yield of ATP / net yield of 2 ATP;
and NADH + H+ / NADH;
aerobic respiration in the presence of oxygen;
pyruvate converted to acetyl CoA;
acetyl CoA enters Krebs cycle;
Krebs cycle yields a small amount of ATP / one ATP per cycle;
and FADH2 / FADH + H+ / NADH / NADH + H+ /
reduced compounds / electron collecting molecules;
these molecules pass electrons to electron transport chain;
oxygen is final electron acceptor / water produced;
electron transport chain linked to creation of an electrochemical gradient;
electrochemical gradient / chemiosmosis powers creation of ATP;
through ATPase;
[8]
2.
(a)
(b)
(i)
increasing fructose 6-phosphate concentration (initially) causes an increase
in activity;
activity levels out / remains constant as (substrate) concentration continues
to rise;
2
(ii)
more collisions with active site as concentration rises;
at high substrate levels all active sites are occupied so no further increase
in rate / enzyme working at maximum rate;
2
(i)
decreases activity;
at all fructose 6-phosphate concentrations;
most effect at intermediate fructose 6-phosphate concentrations / little difference
at high fructose 6-phosphate concentrations;
ATP acts as an inhibitor;
2 max
(ii)
end-product inhibition;
respiration rate decreased if ATP already available;
1 max
[7]
3.
(a)
Award [1] for each of the following clearly drawn and correctly labelled.
outer membrane;
inner membrane – folded into thin cristae;
cristae – shown as thin;
matrix;
intermembrane space – shown as thin;
(70S) ribosomes;
ATP synthase – shown on the inner membrane surface;
(naked) loop of DNA;
4 max
1
(b)
photosynthesis:
chloroplasts / photosystems: for light absorption / photosynthesis;
stroma: light-independent reactions / Calvin cycle;
thylakoid membranes of chloroplast: chemiosmosis /
photophosphorylation / light dependent reactions;
thylakoid space: build up H+ concentration gradient;
inner membrane of thylakoid: electron transfer;
inner membrane: ATP synthesis;
3 max
cell respiration:
3 max
mitochondria: for ATP production / aerobic respiration;
cytoplasm: glycolysis / matrix: Krebs cycle / oxidative
phosphorylation / link reaction;
double / inner membranes of mitochondria: chemiosmosis /
oxidative phosphorylation;
intermembrane space: build-up H+ concentration gradient;
inner membrane of mitochondria: electron transfer;
inner membrane: ATP synthesis;
6 max
Answers must indicate location and process to receive a mark.
Do not award a mark if it is ambiguous whether the candidate is discussing
photosynthesis or respiration.
(c)
a food chain includes a producer and consumers;
represents the direction of energy flow;
energy loss occurs between trophic levels;
due to material not consumed / assimilated;
and from heat loss due to cell respiration;
energy passed on from one level to next is 10–20%;
which limits length of food chain;
photosynthesis / producers convert solar energy to chemical
energy (in organic molecules);
consumers obtain necessary energy from eating organisms
of previous trophic level;
an energy pyramid shows the flow of energy from one tropic
level to the next (in a community);
units are energy per unit area per unit time / J m–2 yr–1;
Pyramid of energy – properly drawn, each level no more than
one fifth the width of the level below it, with three correctly
labelled trophic levels eg producer, primary consumer;
8 max
(Plus up to [2] for quality)
[20]
4.
(a)
between 1.5 and 3.5 hours (or number between these figures)
after feeding mealworm RQ values are higher than for millet;
no difference in RQ values between 3.5 hours and 6 hours;
between 0.5 and 1.5 hours (or number between these figures)
millet RQ values much higher than for mealworm;
between 2 and 3 hours mealworm RQ values are
slightly higher than for millet;
2 max
2
(b)
(c)
millet is not composed entirely of carbohydrates;
millet contains more carbohydrates;
mealworms contain more lipids / proteins;
2 max
(i)
using carbohydrate (from millet as a respiratory substrate)
1
(ii)
reverting to other substrates /
carbohydrates (from millet) used up
1
[6]
5.
Answers must include both similarities and differences to receive full marks.
aerobic requires oxygen and anaerobic does not utilize oxygen;
similarities:
both can start with glucose;
both use glycolysis;
both produce ATP / energy (heat);
both produce pyruvate;
carbon dioxide is produced;
(both start with glycolysis) aerobic leads to Krebs’ cycle and anaerobic
leads to fermentation;
3 max
differences:
anaerobic:
(fermentation) produces lactic acid in humans;
(fermentation) produces ethanol and CO2 in yeast;
occurs in cytoplasm of the cell;
recycles NADH (NAD+);
5 max
aerobic cellular respiration:
pyruvate transported to mitochondria;
further oxidized to CO2 and water (in Krebs’ cycle);
produce a larger amount of ATP (36–38 ATP) / anaerobic produces less ATP (2);
can use other compounds / lipids / amino acids for energy;
[8]
6.
(a)
(i)
A: cristae / inner membrane;
B: matrix;
1
Both needed for [1].
(ii)
A: electron transport / proton transport;
B: Krebs cycle / ATP synthesis;
1
Both needed for [1].
3
(b)
large surface area of cristae allows electron transport / oxidative phosphorylation
to be very efficient;
matrix provides necessary chemical environment for the Krebs cycle;
small distance between inner and outer membranes allows rapid movement
of molecules between cytosol and matrix;
small space between membranes allows protons to be
accumulated / concentrated;
3 max
[5]
7.
glucose converted to pyruvate (two molecules);
by glycolysis;
pyruvate enters the mitochondria;
pyruvate converted to acetyl CoA / ethyl CoA;
by oxidative decarboxylation / NADH and CO2 formed;
fatty acids / lipids converted to acetyl CoA;
acetyl groups enter the Krebs cycle (accept acetyl CoA);
FAD / NAD+ accepts hydrogen (from respiratory substrates) to form NADH / FADH2;
FADH2 / NADH donates electrons / hydrogen to electron transport chain (reject
donates H+);
electrons release energy as they pass along the chain;
oxygen final electron acceptor;
production of water;
builds up proton gradient / protons pumped across inner membrane;
protons flow into matrix of mitochondria through ATPase;
ATP produced;
produces 36 / 38 ATP (per glucose);
Accept any appropriate terminology for NAD and FAD.
(Plus up to [2] for quality)
8 max
[8]
8.
(a)
light dependent and light independent / Calvin cycle
Do not accept “light” and “dark” reactions.
1
4
(b)
Light
low light;
less ATP;
less NADPH + H+;
Carbon dioxide
low carbon dioxide;
less available for fixation in Calvin cycle;
Temperature
enzymes less active at low temperatures;
enzymes denature at high temperatures;
RuBP carboxylase as example;
Do not award mark for factor without effect.
(c)
light excites electrons in chlorophyll / photosystem;
electrons pass along carriers;
protons / H+ pumped across thylakoid membrane / into thylakoid space;
proton / H+ concentration rises inside;
protons / H+ diffuse out / down concentration gradient;
produces ATP from ADP;
involvement of ATP synthetase / synthase;
2 max
3 max
[6]
9.
(a)
(b)
Award [1] for any two products.
ATP;
NADH;
pyruvate;
polar amino acids are hydrophilic and non-polar amino acids
are hydrophobic;
position of polar and non-polar amino acids determine
protein shape / function / location;
(in channel proteins) hydrophilic amino acids line the
channels and allow transport of ions / polar substances;
non-polar amino acids are in contact / embedded
within the lipid membrane;
polar amino acids on the surface proteins make
them water soluble;
non-polar in the centre of water-soluble proteins
stabilize the structure;
Accept any of the above points if clearly explained using a
suitably labelled diagram.
1 max
3 max
[4]
5
10.
(a)
(b)
Award [1] for any two correct examples.
hormones eg insulin;
enzymes eg amylase;
structural eg collagen;
movement eg myosin / actin;
transport eg hemoglobin;
defence eg antibodies / immunoglobin;
2 max
ATP synthesis is coupled to electron transport / H+ movement;
occurs over the (inner) mitochondrial membrane;
electrons are transported through carriers;
energy released by electron transport;
protons / H+ pumped across the membrane;
ATP synthetase transports H+;
uses energy to make ATP;
2 max
[4]
11.
(a)
(b)
(c)
both have two (outer) membranes;
both have cristae;
both have a matrix (with a grainy appearance) / ribosomes;
2 max
shape;
arrangement of cristae;
density of cristae;
amount of matrix granules / any reference to dark dots;
(do not accept ribosomes)
2 max
A / bat’s;
larger size / volume;
greater surface area of cristae / more cristae;
closeness of mitochondria in B mouse reduces rate;
3 max
[7]
12.
(a)
(i)
mitochondrion
(ii)
crista;
1
Award [1] for each of the following, up to [2 max].
folded membrane;
provides large surface area;
for electron transport chain / site of ATP synthesis;
moves protons to inter membrane space from matrix;
3 max
6
(b)
fatty acids oxidized / broken down;
form two-carbon atom (acetyl) fragments;
which are passed to Krebs’ cycle to be metabolized;
2 max
[6]
13.
(a)
ATP;
CO2;
ethanol;
lactic acid;
heat energy;
1
(b)
Reaction
Electrons gained or
lost
Oxygen or hydrogen
gained or lost
Oxidation
Reduction
loss of electrons
gain of electrons;
gain of oxygen /
loss of oxygen /
loss of H+ / hydrogen gain of H+ / hydrogen;
Award [2] for four correct and [1] for two correct.
(c)
2
A – matrix: site for Krebs’ cycle / link reaction / ATP synthesis;
B – inner membrane / cristae: site of oxidative phosphorylation / e– transport
chain / increase surface area / ATP synthesis;
C – inter membrane : H+ / proton build up;
or
C – outer membrane: determines which substances enter the mitochondrion; 3 max
Award [1 max] if only the three labels are given.
[6]
14.
(a)
(b)
2.4 (0.1) mlO2g1 h1 (units required)
1
as temperature rises oxygen consumption decreases / negative
correlation / inverse proportion ( from 6C to 30-32C);
but fairly stable / little effect above 31(1)C; (units required)
2
(c)
temperature below which animals’ oxygen consumption increases /
temperature below which animals respiration rate increases (to maintain body
temperatures);
temperature at which animal reaches minimal oxygen consumption /
temperature above which oxygen consumption remains steady / possible
increase;
1 max
(d)
(i)
sloth
1
7
(ii)
eg at 17C has 100% of metabolic rate and at  20C has 280
(5)% (of metabolic rate) / a change in 37C corresponds to a
change of 180(5)% (of metabolic rate);
180  37 = 4.9 (0.2)% (of metabolic rate) per degree of temperature
change / C1;
2 max
Award full marks for correct calculation of slope using other
figures.
Award [1] in case of ECF of a correct calculation with
incorrect figures.
(e)
(f)
(g)
(h)
to produce heat;
maintain constant body temperature;
1 max
tropical mammals have a greater increase in metabolic rate as the
temperature drops / arctic mammals have a (more) gradual change
in metabolic rate as temperature drops;
tropical mammals have a higher lower critical temperature;
values for arctic mammals are extrapolated / estimated / not proven / less
certain;
tropical mammals are not (as well) adapted to cold temperatures / they
live where little temperature change occurs;
arctic mammals have more / thicker fur / more insulation to help keep
warm;
tropical mammals use BMR to regulate temperature more than arctic
mammals;
3 max
(i)
65.0  32.5 = 32.5(0.5) mm (units required)
(ii)
the values for thickness are only of length and not the density /
number of hairs per surface area (that could be greater in the reindeer);
does not include thickness of each hair (that could be greater in the
reindeer) / different compositions / materials;
does not include amount of air trapped in fur for insulation (that
could be greater in the reindeer);
different colours of hair affect absorption light energy;
1 max
(i)
beaver drops by about 1.9 (0.1)W dm−2 / from 2.05(0.05)W dm−2 to
about 0.20(0.05)Wdm−2 (units required)
(ii)
increase in metabolic rate (to generate heat);
fat insulation (to maintain heat);
fast muscle movements (to generate heat);
vasoconstriction / decreased blood flow to surface;
1
1
1 max
Accept any other reasonable suggestion.
8
(i)
(increases in) both are adaptations to maintain body temperature;
mammals are homeotherms / must maintain constant body temperature;
increased metabolic rate produces more energy to maintain body temperatures;
thicker the fur, the greater the insulation value;
animals with high fur thickness do not change BMR as quickly as animals with
lower fur thickness;
examples of animals with greater fur thickness and lower critical temperatures;
greater fur thickness, less need for increased metabolic rate to maintain
temperature / less fur thickness requires higher metabolic rate to maintain body
temperature;
thicker fur saves energy stores during cold temperatures when food is scarce;
animals in two data sets are not identical / insufficient data;
3 max
[18]
15.
(a)
as cadmium ion concentration increases, respiration rate decreases
1
(b)
at 50 mol dm−3 respiration is lower than at 0 mol dm−3 for all temperatures;
at50 mol dm−3 respiration is highest at 15C, whereas at 0 mol dm−3 respiration
is highest at 25;
respiration at 35C is lowest at both cadmium concentrations;
2 max
(c)
salinity / pH / clarity / oxygen level / pollution
(d)
data shows results only for cadmium, not for all trace elements;
the hypothesis is always supported for changes of temperature from 15 / 25 to
35C;
the hypothesis is not always supported from 15 to 25C;
at 35C the effect on respiration is greatest at all cadmium levels;
may be other factors causing the respiration to fall (such as activity of
enzymes);
marine temperatures unlikely to reach 35C;
3 max
1
[7]
16.
(a)
210 ml kg–1 min–1 (2) (units required)
1
(b)
Accept 86 (2) or 46 (2)
1
9
(c)
oxygen delivery is similar to healthy;
oxygen use is lower / half;
insufficient energy / ATP produced by aerobic respiration;
forced to respire anaerobically;
lactic acid builds up;
3 max
[5]
17.
(a)
(b)
(c)
Q: anaerobic respiration / fermentation;
R: aerobic respiration / Kreb’s (citric acid) cycle;
2
A: pyruvate / 3-oxopropanoate;
D: carbon dioxide;
2
mitochondrion;
1
[5]
18.
(a)
(b)
(c)
(i)
carbon dioxide and water
Need both to receive the mark.
1
(ii)
heat / energy
1
starch is broken down transforming into sugar;
chlorophyll is broken down so bananas change from green to yellow;
increase in respiration causes water release and CO2 formation;
2 max
reduce heat of cargo / refrigerate (bananas) to slow respiration rate;
lower oxygen / raise nitrogen / carbon dioxide level in cargo
atmosphere to inhibit respiration rate;
shorten transport distance / time so less time to over ripen;
2 max
[6]
10