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Respiration releases chemical energy in biological processes: Eduqas A‑Level Biology questions

Every Eduqas A-Level Biology exam question on 1.3 Respiration releases chemical energy in biological processes, 2016–2025, with its mark scheme and examiner’s report.

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2,061 questions

  1. Q1(a)(i)

    June 2025 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 1(a)(i): Name two hydrogen carriers that are involved in aerobic respiration in mitochondria. [1]

  2. Q5(a)(i)

    June 2025 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 5(a)(i): Name the stage of respiration that takes place in the cytoplasm. [1]

  3. Q5(a)(ii)

    June 2025 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 5(a)(ii): State the type of reaction that produces ATP in the cytoplasm. [1] Image 5.1 shows the stages of respiration that take place in the mitochondria. Image 5.1 pyru

  4. Q5(a)(iii)

    June 2025 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 5(a)(iii): Name two types of enzyme involved in the conversion of pyruvate to acetyl CoA in the stage labelled X in Image 5.1. [1]

  5. Q5(a)(iv)

    June 2025 · Component 1

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 5(a)(iv): Triacetin is a triglyceride that can be used as an alternative respiratory substrate to glucose. From each molecule of triacetin, four molecules of acetyl CoA a

  6. Q5(b)(i)

    June 2025 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 5(b)(i): Explain why the molecules shown in Image 5.2 are structural isomers. [1]

  7. Q5(c)(i)

    June 2025 · Component 1

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2025 Component 1, question 5(c)(i): Use information from Image 5.3 to state whether NAD is being oxidised or reduced in the reaction labelled X. Explain your answer. [2]

  8. Q5(d)(iii)

    June 2025 · Component 1

    3 marks1.3 Respiration releases chemical energy in biological processesC.4 Biological reactions are regulated by enzymes
    The whole paper ↗
    June 2025 Component 1, question 5(d)(iii): The rate at which NADH transports hydrogen to the electron transport chain increases as the concentration of ATP in the matrix decreases. ATP cannot be stored i

  9. Q3(a)(ii)

    June 2024 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 1, question 3(a)(ii): Name the type of respiration shown in Image 3.1. [1]

  10. Q3(a)(iii)

    June 2024 · Component 1

    4 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 1, question 3(a)(iii): In Image 3.1, C1, C2, C3 and C6 indicate the number of carbon atoms in different organic molecules. I. Name the molecules that contain 1, 2 and 3 carbon atoms.

  11. Q3(a)(iv)

    June 2024 · Component 1

    3 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 1, question 3(a)(iv): If yeast cells respire for a long time using the process summarised in Image 3.1 they eventually die. When animal cells respire in a similar way it does not cau

  12. Q3(b)(i)

    June 2024 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 1, question 3(b)(i): Both test tubes were left in the water bath for 5 minutes in step 3. Explain why this was necessary. [1]

  13. Q3(b)(ii)

    June 2024 · Component 1

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 1, question 3(b)(ii): Explain the purpose of the layer of oil. [2]

  14. Q3(a)(i)

    June 2024 · Component 2

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 2, question 3(a)(i): Red blood cells do not contain mitochondria. Use all the information given to conclude why red blood cells are at greater risk of membrane damage than other bod

  15. Q4(b)(i)

    June 2024 · Component 2

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 2, question 4(b)(i): Calculate the mean whole body oxygen demand per g of fish. Write your answer in the space in Table 4.2.  [2]

  16. Q4(b)(ii)

    June 2024 · Component 2

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2024 Component 2, question 4(b)(ii): Explain why the units for oxygen demand are given per gram of fish.  [1] The oxygen demand shows that the eyes in the surface form use approximately 11% of the

  17. Q3(b)(i)

    June 2023 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2023 Component 1, question 3(b)(i): Name the process by which ATP is produced directly in glycolysis. [1]

  18. Q3(b)(ii)

    June 2023 · Component 1

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2023 Component 1, question 3(b)(ii): Use Image 3.1 to explain why there is a net yield of 2 ATP produced directly in glycolysis. [2]

  19. Q3(b)(iii)

    June 2023 · Component 1

    2 marks1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2023 Component 1, question 3(b)(iii): Identify one type of enzyme involved in the conversion of triose phosphate to pyruvate and state the function of this type of enzyme. [2]

  20. Q3(b)(iv)

    June 2023 · Component 1

    1 mark1.3 Respiration releases chemical energy in biological processes
    The whole paper ↗
    June 2023 Component 1, question 3(b)(iv): Describe what happens to pyruvate in animal cells under anaerobic conditions. [1]
All 55 questions on Respiration releases chemical energy in biological processes, as a list
  1. June 2025, Component 1, Q1(a)(i) (1 mark): Name two hydrogen carriers that are involved in aerobic respiration in mitochondria. [1]
  2. June 2025, Component 1, Q5(a)(i) (1 mark): Name the stage of respiration that takes place in the cytoplasm. [1]
  3. June 2025, Component 1, Q5(a)(ii) (1 mark): State the type of reaction that produces ATP in the cytoplasm. [1] Image 5.1 shows the stages of respiration that take place in the mitochondria. Image 5.1 pyru
  4. June 2025, Component 1, Q5(a)(iii) (1 mark): Name two types of enzyme involved in the conversion of pyruvate to acetyl CoA in the stage labelled X in Image 5.1. [1]
  5. June 2025, Component 1, Q5(a)(iv) (2 marks): Triacetin is a triglyceride that can be used as an alternative respiratory substrate to glucose. From each molecule of triacetin, four molecules of acetyl CoA a
  6. June 2025, Component 1, Q5(b)(i) (1 mark): Explain why the molecules shown in Image 5.2 are structural isomers. [1]
  7. June 2025, Component 1, Q5(c)(i) (2 marks): Use information from Image 5.3 to state whether NAD is being oxidised or reduced in the reaction labelled X. Explain your answer. [2]
  8. June 2025, Component 1, Q5(d)(iii) (3 marks): The rate at which NADH transports hydrogen to the electron transport chain increases as the concentration of ATP in the matrix decreases. ATP cannot be stored i
  9. June 2024, Component 1, Q3(a)(ii) (1 mark): Name the type of respiration shown in Image 3.1. [1]
  10. June 2024, Component 1, Q3(a)(iii) (4 marks): In Image 3.1, C1, C2, C3 and C6 indicate the number of carbon atoms in different organic molecules. I. Name the molecules that contain 1, 2 and 3 carbon atoms.
  11. June 2024, Component 1, Q3(a)(iv) (3 marks): If yeast cells respire for a long time using the process summarised in Image 3.1 they eventually die. When animal cells respire in a similar way it does not cau
  12. June 2024, Component 1, Q3(b)(i) (1 mark): Both test tubes were left in the water bath for 5 minutes in step 3. Explain why this was necessary. [1]
  13. June 2024, Component 1, Q3(b)(ii) (2 marks): Explain the purpose of the layer of oil. [2]
  14. June 2024, Component 2, Q3(a)(i) (2 marks): Red blood cells do not contain mitochondria. Use all the information given to conclude why red blood cells are at greater risk of membrane damage than other bod
  15. June 2024, Component 2, Q4(b)(i) (2 marks): Calculate the mean whole body oxygen demand per g of fish. Write your answer in the space in Table 4.2.  [2]
  16. June 2024, Component 2, Q4(b)(ii) (1 mark): Explain why the units for oxygen demand are given per gram of fish.  [1] The oxygen demand shows that the eyes in the surface form use approximately 11% of the
  17. June 2023, Component 1, Q3(b)(i) (1 mark): Name the process by which ATP is produced directly in glycolysis. [1]
  18. June 2023, Component 1, Q3(b)(ii) (2 marks): Use Image 3.1 to explain why there is a net yield of 2 ATP produced directly in glycolysis. [2]
  19. June 2023, Component 1, Q3(b)(iii) (2 marks): Identify one type of enzyme involved in the conversion of triose phosphate to pyruvate and state the function of this type of enzyme. [2]
  20. June 2023, Component 1, Q3(b)(iv) (1 mark): Describe what happens to pyruvate in animal cells under anaerobic conditions. [1]
  21. June 2022, Component 1, Q2(a)(iii) (4 marks): ATP acts as a common energy source for reactions in the cells of all living organisms. Most ATP in eukaryotic cells is synthesised in the mitochondria. Describe
  22. June 2022, Component 1, Q4(a)(i) (2 marks): Calculate the efficiency of aerobic respiration of glucose. Give your answer to a suitable number of decimal places. [2] Efficiency of aerobic respiration = %
  23. June 2022, Component 1, Q4(a)(ii) (1 mark): State what happens to the energy which is not used to generate ATP. [1]
  24. June 2022, Component 1, Q4(a)(iii) (3 marks): Table 4.1 compares figures from the respiration of carbohydrate and lipid. Table 4.1 Energy released Metabolic water Oxygen consumed Energy source / kJ g–1 food
  25. June 2022, Component 1, Q4(b)(i) (2 marks): Lipids are digested into glycerol, a three carbon compound, and fatty acids. The fatty acids are then broken down further in the liver into two carbon fragments
  26. June 2022, Component 1, Q4(b)(ii) (3 marks): Before proteins can enter the respiratory pathway they must be hydrolysed. Describe how proteins are hydrolysed and suggest which stage of respiration the produ
  27. Autumn 2021, Component 1, Q6(a)(ii) (3 marks): Explain why blood lactate concentration rises as a symptom of cyanide poisoning.  [3]
  28. Autumn 2021, Component 1, Q6(b) (3 marks): Apple seeds (pips) contain cyanide. If an apple seed is swallowed whole, it passes through the gut and will not poison the animal. If the seed is chewed cyanide
  29. Autumn 2020, Component 1, Q3(b)(i) (2 marks): state what is meant by substrate level phosphorylation; [2]
  30. Autumn 2020, Component 1, Q6(a)(i) (1 mark): The tap is open when the apparatus is assembled. [1]
  31. Autumn 2020, Component 1, Q6(a)(ii) (1 mark): The tap is not closed until 5 minutes after setting up. [1]
  32. Autumn 2020, Component 1, Q6(a)(iii) (1 mark): No readings are taken before the Janus Green indicator changes to pink. [1]
  33. Autumn 2020, Component 1, Q6(b) (2 marks): Explain why you would expect the meniscus to move in the direction of the arrow. [2]
  34. Autumn 2020, Component 1, Q6(c) (3 marks): Suggest a suitable control experiment and explain why a control is necessary. [3]
  35. Autumn 2020, Component 1, Q6(d)(i) (3 marks): The results when glucose was used as the substrate are shown in the table below. Use the table and formula to calculate the standard deviation for the glucose r
  36. Autumn 2020, Component 1, Q6(d)(ii) (3 marks): Complete the following table which shows the results of the experiment for all three sugars. [3] Standard Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Mean deviation
  37. Autumn 2020, Component 1, Q6(d)(iii) (3 marks): State what standard deviation indicates about data and comment on the values for the three sugars in this experiment. [3]
  38. Autumn 2020, Component 1, Q6(e) (2 marks): Explain why the respiratory rate is much slower when yeast uses sucrose as the respiratory substrate. [2]
  39. Autumn 2020, Component 1, Q6(f) (2 marks): Predict what would happen to the position of the meniscus if the yeast was only carrying out aerobic respiration. Explain your answer. [2]
  40. June 2019, Component 1, Q4(b)(i) (2 marks): Explain why the cell uses inhibition of PFK as the main method of slowing glycolysis, rather than using the inhibition of HK. [2] 3-BrPA is a chemical which is
  41. June 2019, Component 1, Q4(b)(ii) (3 marks): Explain how 3-BrPA acts as a potential anti-cancer agent. [3]
  42. June 2019, Component 1, Q4(c)(ii) (2 marks): Explain why pyruvate was used as the respiratory substrate and not glucose. [2] The results of the experiment are shown in the table below. Time taken for methy
  43. June 2019, Component 2, Q6(b) (3 marks): Give the word equation for anaerobic respiration in yeast. Explain why it is less efficient than aerobic respiration for the yeast but essential to the brewing
  44. June 2019, Component 3, Q6(c)(i) (2 marks): Earthworms rely on glucose as their main respiratory substrate and can respire glucose both aerobically and anaerobically. State the maximum yield of ATP from o
  45. June 2019, Component 3, Q9(c)(i) (3 marks): Using figure 9.4 and your own knowledge, explain the shape of the graph for ATP and creatine phosphate and explain why aerobic respiration takes over from anaer
  46. June 2018, Component 1, Q1(b)(i) (2 marks): Calculate the efficiency of ATP production from glucose for the figures above. Give your answer to one decimal place. [2] Efficiency = %
  47. June 2018, Component 1, Q1(b)(ii) (1 mark): The efficiency of an electric motor or petrol engine is between 10% and 20%. Use the result from your calculation to make a quantitative conclusion about the ef
  48. June 2018, Component 1, Q1(d) (3 marks): The diagram below shows the use of ATP from three sources over a 5 hour period, whilst undertaking exercise. stored ATP Aerobic oxidation Anaerobic glycolysis 0
  49. June 2018, Component 1, Q5(a)(iii) (4 marks): With reference to the biochemical pathways of photosynthesis and respiration, explain how a light absorbance of 0 a.u. could be observed in this experiment. [4]
  50. June 2018, Component 1, Q7 (9 marks): More than a billion years ago, aerobic bacteria colonised primordial eukaryotic cells that lacked the ability to use oxygen metabolically. A symbiotic relations
  51. June 2017, Component 1, Q8(a)(i) (2 marks): Describe the stage of the biochemical pathway in the cytoplasm which produces reduced NAD. [2] The energy budget for the complete oxidation of a single glucose
  52. June 2017, Component 1, Q8(a)(ii) (2 marks): Explain why the ATP yield per glucose molecule will be decreased if mechanism B is used. [2]
  53. June 2017, Component 1, Q8(a)(iii) (2 marks): Explain why mechanism A would be used in the muscle of flying insects. [2]
  54. June 2017, Component 1, Q8(b) (3 marks): If a human eats a diet low in nutrients, amino acids from muscle tissue can be used as an alternative respiratory substrate. The amino acids, when processed, pr
  55. June 2017, Component 1, Q9 (9 marks): Biochemical reactions in cells often involve cyclic metabolic pathways which occur within compartments inside cells. Compare the Krebs cycle and Calvin cycle in

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