C1.2 Cell respiration

a. used as a source/(temporary) store of energy / is the energy currency of the cell;

b. releases energy when converted to ADP/when a phosphate is removed;

c. amount of energy released can be used/sufficient for (many metabolic) tasks;

d. active transport/another valid example;

e. ATP to ADP conversion is reversible / ATP can be regenerated from ADP;

f. can be produced in different ways/using energy from different sources/by aerobic or anaerobic respiration;

g. stable within cell so does not release energy prematurely/before needed;

h. small molecule/soluble so can move easily/quickly (through the cell);

i. cannot diffuse through membranes so is not lost from cell/to the environment;

h. The idea of ATP being small/soluble
must be there along with its
moveability.

3

Marking guidance:

max

a. movement of cells/chromosomes and example of movement;
b. movement of flagellum/cilium;
c. endocytosis/exocytosis;
d. detachment of myosin heads from actin filaments / myosin heads change their angle/become cocked;
e. active transport and example of use of active transport;
f. anabolic reactions / polymerization example / example of synthesizing macromolecules;
g. generation of heat and to provide optimum temperature for enzyme activity / in homeostasis / to maintain body temperature;
h. phosphorylation of substrates in glycolysis;
i. phosphorylation of substrates in photosynthesis light-
independent reaction/Calvin cycle;

For a. accept descriptions of cells (e.g. amoeboid phagocyte
moving to site of infection) or chromosomes (e.g. anaphase,
chromosomes moving to opposite poles).
For d. ignore 'muscle contraction'.
For e. E.g. sodium-potassium pump (in neurons) / maintaining resting potential in neurons / generation of root pressure / villus epithelial cells / selective reabsorption in kidney.
For e. do not accept transport of large molecules as example.
For f. accept examples such as DNA replication / transcription / translation / and other examples of formation of
macromolecules.
For h. accept phosphorylation of glucose (to glucose-6-phosphate) or phosphorylation of fructose-6-phosphate (to
fructose 1,6-biphosphate).
For i. accept formation of triose phosphate and formation of ribulose bisphosphate (regeneration of RuBP).

5

Marking guidance:

max

A

The need for energy

a. life processes/active transport/metabolism/movement require energy;

b. ATP provides energy for cell processes;

c. energy need to break bonds in a substrate during enzyme reactions;

d. energy is required to synthesize ATP from ADP

OR

energy is released when ATP is hydrolysed;

Release of energy

e. cell respiration produces ATP using energy stored in carbon compounds/glucose/fatty acids;

f. aerobic respiration occurs in mitochondria;

g. aerobic respiration requires oxygen;

h. aerobic respiration provides more ATP/energy than anaerobic respiration;

i. cells use mainly glucose and/or fatty acids as a fuel/substrate for respiration;

j. in aerobic respiration carbon dioxide and water are waste products

OR
$$\text { fuel/glucose }+\mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \text { (+ energy/ATP); }$$

k. anaerobic respiration (in humans) yields lactic acid as a waste product

OR

fuel/glucose → lactic acid (+ energy/ATP);

Correct equation can gain
marking points g. and j.
Equation does not need to be balanced.

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Marking guidance:

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anaerobic respiration: glucose transformed into (two molecules of) pyruvate/pyruvic acid; Accept this point in any part of the answer. oxidation reactions using NAD/NAD ${ }^{+}$/ producing reduced NAD/NADH; smaller amount of energy released/ATP produced than in aerobic; $\mathrm{NAD} / \mathrm{NAD}^{+}$regenerated by reducing pyruvate/transfer of hydrogen to pyruvate; pyruvate to $\mathrm{CO}_{2}$ and ethanol in yeast/in alcoholic fermentation; pyruvate to lactic acid in humans/in lactic/lactate fermentation; aerobic respiration:
pyruvic acid/pyruvate fully oxidized/fully broken down; by the link reaction and Krebs cycle; reduced NAD/NADH passes electrons to electron transport chain; proton $/ \mathrm{H}^{+}$gradient generated; oxygen required as terminal electron acceptor; proton gradient used by ATP synthase/synthetase to produce ATP;

a. more oxygen in inhaled air than in exhaled air

OR

mouse uses oxygen in respiration

b. carbon dioxide exhaled / produced by mouse is absorbed by the soda lime

c. difference in volume is oxygen used by mouse

OR the volume/concentration/pressure of oxygen in the jar falls

d. «this» sucks the coloured liquid up the tube

e. volume of oxygen consumed equals the increase in volume of coloured water in the tube

Source/mouse must be mentioned for marking point b - not just "sodalime absorbs $\mathrm{CO}_{2}$ ".

3 max