AS & A Level Biology 9700 · Topic 12

Energy and respiration: past paper questions

162 real questionsasked in 10 of the last 10 exam series2019–2025usually: Suggest, Describe, Explain, State, Name

Real questions on energy and respiration

The newest 20 of 145 written questions, plus 17 multiple-choice. Open one to see it on the real paper.

9700/43 · October/November 2025 · Q7a[3]
Outline the features of ATP that make it suitable as the universal energy currency.
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9700/43 · October/November 2025 · Q7b[6]
Rotenone is a compound that affects oxidative phosphorylation. Suggest and explain how rotenone reduces the production of ATP and water in aerobic respiration. Rotenone disrupts the first carrier in the electron transport chain by stopping the transfer of electrons from this carrier.
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9700/41 · May/June 2025 · Q1a[2]
Name two energy-rich molecules that enter the respiration pathway to synthesise ATP.
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9700/41 · May/June 2025 · Q1b[4]
NH 2 O HO O P O O – P O – N O O P O N O O – OH N N OH Fig. 1.1 Explain the features of ATP that make it suitable to be the universal energy currency of cells. (b) Fig. 1.1 shows a molecule of ATP.
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9700/41 · May/June 2025 · Q1d(i)[1]
Pyruvate moves into the matrix of the mitochondrion only when a particular inorganic molecule is present. Name the inorganic molecule that must be present in the cell for pyruvate to enter the matrix of the mitochondrion.
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9700/41 · May/June 2025 · Q1d(ii)[3]
Explain how the presence of the inorganic molecule named in (d)(i) affects the ATP yield from respiration.
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9700/41 · May/June 2025 · Q2a[4]
Explain how the experimental set-up in Fig. 2.2 allows the rate of respiration of woodlice to be determined.
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9700/41 · May/June 2025 · Q2b[1]
A student determined the rate of respiration of woodlice at a temperature of 5 °C and at a temperature of 20 °C. Predict and explain how the rate of respiration of woodlice differs at 5 °C compared to 20 °C.
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9700/42 · May/June 2025 · Q1b[4]
Cyanide ions (CN – ) are highly toxic. Cyanide ions bind to carrier 4 in Fig. 1.1 and inactivate the carrier. Suggest and explain how the binding of cyanide ions to carrier 4 can have an effect on respiration.
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9700/43 · May/June 2025 · Q1b[4]
The mitochondrial pyruvate carrier (MPC), shown in Fig. 1.1, allows the passage of pyruvate into the mitochondrial matrix. When pyruvate enters the mitochondrial matrix, it takes part in the link reaction. Describe the link reaction.
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9700/43 · May/June 2025 · Q1c[3]
Some tumour cells have a greatly reduced ability to transport pyruvate into the matrix of the mitochondrion. Suggest how a reduction in pyruvate transport could affect respiration in these tumour cells.
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9700/42 · February/March 2025 · Q1a[1]
Different types of respiratory substrate can have different energy values and therefore release different quantities of energy when they are respired. Complete Table 1.1 to show the energy value of each of the three main types of respiratory substrate. Use one tick (3) to identify which of the two possible energy value...
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9700/42 · February/March 2025 · Q1b(i)[1]
State the name of the laboratory apparatus that can be used to determine the RQ value of organisms such as blowfly larvae.
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9700/42 · February/March 2025 · Q1b(ii)[1]
When determining RQ values using the laboratory apparatus stated in (b)(i), chemicals such as soda lime or potassium hydroxide solution are used. State the reason for using chemicals such as soda lime or potassium hydroxide solution when measuring RQ values.
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9700/42 · February/March 2025 · Q1c(i)[1]
Calculate how many molecules of oxygen are taken in when one molecule of malic acid is respired aerobically. number of molecules of oxygen =
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9700/42 · February/March 2025 · Q1c(ii)[1]
Calculate the RQ for malic acid. Give your answer to two decimal places. RQ =
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9700/42 · February/March 2025 · Q1d(i)[3]
Describe the trend shown during torpor in Fig. 1.3 and suggest an explanation for this trend.
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9700/42 · February/March 2025 · Q1d(ii)[2]
Deer mice have a daily period of torpor only at certain times of the year. Suggest reasons why a deer mouse enters torpor only at certain times of the year.
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9700/42 · February/March 2025 · Q6a(i)[3]
Identify P, Q and R. P Q
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9700/42 · February/March 2025 · Q8a[2]
In the link reaction, a two-carbon acetyl group is produced from pyruvate. The acetyl group is transferred to coenzyme A to form acetyl coenzyme A (acetyl-coA). State the terms used to summarise the two chemical changes that occur in the link reaction to produce an acetyl group from pyruvate.
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What examiners said

Candidates were asked to identify the approximate energy value of three main respiratory substrates. Few were aware that lipid has the highest energy value.
— Examiner report, February/March 2025, 9700/42 Q1(a) (Cambridge)

(i)(ii) Most candidates were able to state the name of the apparatus that can be used to determine RQ values. Many were able to state the reasons for using chemicals such as soda lime or potassium hydroxide solution.
— Examiner report, February/March 2025, 9700/42 Q1(b) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

Practise energy and respiration

In the syllabus

12.1 Energy

outline the need for energy in living organisms, as illustrated by active transport, movement and anabolic reactions, such as those occurring in DNA replication and protein synthesis
describe the features of ATP that make it suitable as the universal energy currency
state that ATP is synthesised by: • transfer of phosphate in substrate-linked reactions • chemiosmosis in membranes of mitochondria and chloroplasts
explain the relative energy values of carbohydrates, lipids and proteins as respiratory substrates
state that the respiratory quotient (RQ) is the ratio of the number of molecules of carbon dioxide produced to the number of molecules of oxygen taken in, as a result of respiration
calculate RQ values of different respiratory substrates from equations for respiration
describe and carry out investigations, using simple respirometers, to determine the RQ of germinating seeds or small invertebrates (e.g. blowfly larvae)

12.2 Respiration

State where each of the four stages in aerobic respiration occurs in eukaryotic cells: • glycolysis in the cytoplasm • link reaction in the mitochondrial matrix • Krebs cycle in the mitochondrial matrix • oxidative phosphorylation on the inner membrane of mitochondria
outline glycolysis as phosphorylation of glucose and the subsequent splitting of fructose 1,6-bisphosphate (6C) into two triose phosphate molecules (3C), which are then further oxidised to pyruvate (3C), with the production of ATP and reduced NAD
explain that, when oxygen is available, pyruvate enters mitochondria to take part in the link reaction
describe the link reaction, including the role of coenzyme A in the transfer of acetyl (2C) groups
outline the Krebs cycle, explaining that oxaloacetate (4C) acts as an acceptor of the 2C fragment from acetyl coenzyme A to form citrate (6C), which is converted back to oxaloacetate in a series of small steps
explain that reactions in the Krebs cycle involve decarboxylation and dehydrogenation and the reduction of the coenzymes NAD and FAD
describe the role of NAD and FAD in transferring hydrogen to carriers in the inner mitochondrial membrane
explain that during oxidative phosphorylation: • hydrogen atoms split into protons and energetic electrons • energetic electrons release energy as they pass through the electron transport chain (details of carriers are not expected) • the released energy is used to transfer protons across the inner mitochondrial membrane • protons return to the mitochondrial matrix by facilitated diffusion through ATP synthase, providing energy for ATP synthesis (details of ATP synthase are not expected) • oxygen acts as the final electron acceptor to form water
describe the relationship between the structure and function of mitochondria using diagrams and electron micrographs
outline respiration in anaerobic conditions in mammals (lactate fermentation) and in yeast cells (ethanol fermentation) continued

12.2 Respiration continued

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