IGCSE Biology Topic 12: Respiration MCQs – 30 Practice Questions with Answers (Cambridge 0610)

Free practice for Cambridge IGCSE Biology 0610 on respiration, covering the uses of released energy, aerobic respiration, anaerobic respiration in yeast and muscle, and oxygen debt, with every question followed by a worked explanation.

What respiration is and what its energy is used for

Q1. Which description best fits respiration?

  • (A) The movement of air in and out of the lungs
  • (B) The diffusion of gases across the alveoli
  • (C) The transport of oxygen around the body in the blood to respiring tissues
  • (D) The chemical reactions in cells that release energy from nutrients
Show Answer

Answer: D – Respiration is a set of chemical reactions inside cells that releases energy from nutrients.

Q2. How does respiration differ from breathing?

  • (A) Breathing releases energy, while respiration moves air
  • (B) Breathing moves air, while respiration is a chemical process in cells
  • (C) Breathing happens inside cells, while respiration happens in the lungs and the blood
  • (D) Breathing uses oxygen, while respiration never uses oxygen
Show Answer

Answer: B – Breathing is ventilation of the lungs, whereas respiration is the chemical release of energy in cells.

Q3. Which process in muscle cells is powered directly by energy from respiration?

  • (A) Muscle contraction
  • (B) Diffusion of oxygen into the blood
  • (C) Filtration of blood in the kidney
  • (D) Secretion of mucus in the airways
Show Answer

Answer: A – Energy from respiration powers muscle contraction, including the muscles used in movement.

Q4. Which cell process builds new proteins and therefore needs energy from respiration?

  • (A) The beating of cilia in the airways
  • (B) The diffusion of carbon dioxide out of cells
  • (C) Protein synthesis
  • (D) The evaporation of water from leaves
Show Answer

Answer: C – Building new proteins from amino acids needs energy supplied by respiration.

Q5. Which process in a cell directly needs energy from respiration because it moves substances against a concentration gradient?

  • (A) Diffusion
  • (B) Osmosis
  • (C) Evaporation
  • (D) Active transport
Show Answer

Answer: D – Active transport moves substances against their concentration gradient, so it requires energy from respiration.

Q6. Which process, involving the production of new cells, needs energy from respiration?

  • (A) The clotting of blood at a wound
  • (B) Cell division
  • (C) The dissolving of food by stomach acid
  • (D) The absorption of light by chlorophyll
Show Answer

Answer: B – Cell division, including the copying of cell contents and growth that follows, needs energy from respiration.

Q7. Which activity in nerve cells is powered by energy from respiration?

  • (A) The passage of nerve impulses
  • (B) The diffusion of glucose into cells
  • (C) The loss of heat from the skin
  • (D) The filtering of urea from the blood
Show Answer

Answer: A – Energy from respiration powers the passage of nerve impulses along nerve cells.

Q8. How does respiration help an animal maintain a constant body temperature?

  • (A) It stores heat in the bones for later use
  • (B) It stops all heat loss from the skin
  • (C) It releases energy, some of which warms the body
  • (D) It cools the blood as it passes through the lungs
Show Answer

Answer: C – Maintaining a constant body temperature is one of the uses of energy released by respiration.

Q9. In an investigation of respiration in yeast at different temperatures, what pattern is expected as temperature rises from cold towards warm?

  • (A) The rate falls steadily at every temperature
  • (B) The rate rises, then falls sharply at high temperatures
  • (C) The rate stays exactly the same at every temperature
  • (D) The rate rises without limit at every temperature
Show Answer

Answer: B – Warming speeds up respiration in yeast up to an optimum, but very high temperatures reduce the rate sharply.

Q10. In an investigation of the effect of temperature on respiration in yeast, which variable must be changed while the others are kept the same?

  • (A) The type of yeast used in each sample
  • (B) The volume of yeast suspension in each sample
  • (C) The amount of glucose supplied to each sample
  • (D) The temperature of each sample
Show Answer

Answer: D – Temperature is the variable being investigated, so it is the one changed while other conditions are controlled.

Aerobic respiration

Q11. Which description best fits aerobic respiration?

  • (A) The chemical reactions in cells that use oxygen to release energy from nutrients
  • (B) The chemical reactions in cells that break down nutrients without using any oxygen at all
  • (C) The movement of oxygen from the alveoli into the blood
  • (D) The breakdown of food in the gut by enzymes
Show Answer

Answer: A – Aerobic respiration uses oxygen to break down nutrient molecules and release energy.

Q12. What is the word equation for aerobic respiration?

  • (A) Glucose → lactic acid
  • (B) Glucose → alcohol + carbon dioxide
  • (C) Glucose + oxygen → carbon dioxide + water
  • (D) Carbon dioxide + water → glucose + oxygen
Show Answer

Answer: C – In aerobic respiration, glucose and oxygen react to give carbon dioxide and water, releasing energy.

Q13. What is the balanced chemical equation for aerobic respiration?

  • (A) C6H12O6 → 2C2H5OH + 2CO2
  • (B) C6H12O6 + 6O2 → 6CO2 + 6H2O
  • (C) 6CO2 + 6H2O → C6H12O6 + 6O2
  • (D) C6H12O6 → 2C3H6O3
Show Answer

Answer: B – One glucose molecule reacts with six oxygen molecules to give six molecules each of carbon dioxide and water.

Q14. How does the energy released per glucose molecule in aerobic respiration compare with anaerobic respiration?

  • (A) Aerobic respiration releases much more energy per glucose molecule
  • (B) Aerobic respiration releases much less energy per glucose molecule
  • (C) Both release exactly the same energy per glucose molecule
  • (D) Aerobic respiration releases no energy at all
Show Answer

Answer: A – Aerobic respiration breaks glucose down fully, releasing much more energy per molecule than anaerobic respiration.

Q15. In the aerobic respiration equation, which substance is the nutrient molecule broken down?

  • (A) Oxygen
  • (B) Carbon dioxide
  • (C) Water
  • (D) Glucose
Show Answer

Answer: D – Glucose is the nutrient molecule broken down, using oxygen, to release energy.


Q16. Why does a cell that respires aerobically need a continuous supply of oxygen?

  • (A) Oxygen is stored in the cell as a fuel reserve for later use in respiration
  • (B) Oxygen is needed to build new cell membranes
  • (C) Oxygen is a reactant that breaks down glucose to release energy
  • (D) Oxygen is needed to cool the cell during respiration
Show Answer

Answer: C – Without oxygen as a reactant, the cell cannot carry out aerobic respiration and must rely on anaerobic respiration.

Q17. A muscle cell has a plentiful oxygen supply during gentle activity. Which type of respiration will it mainly carry out?

  • (A) Fermentation in the gut
  • (B) Aerobic respiration
  • (C) Anaerobic respiration to lactic acid
  • (D) Photosynthesis
Show Answer

Answer: B – With oxygen available, cells mainly respire aerobically because it releases much more energy per glucose molecule.

Q18. In the balanced equation for aerobic respiration, how many oxygen molecules react with one glucose molecule?

  • (A) 6
  • (B) 2
  • (C) 1
  • (D) 12
Show Answer

Answer: A – The balanced equation is C6H12O6 + 6O2 → 6CO2 + 6H2O.

Q19. In the balanced equation for aerobic respiration, how many carbon dioxide molecules are produced from one glucose molecule?

  • (A) 1
  • (B) 2
  • (C) 12
  • (D) 6
Show Answer

Answer: D – The balanced equation shows six carbon dioxide molecules produced per glucose molecule.

Q20. In the balanced equation for aerobic respiration, how many water molecules are produced from one glucose molecule?

  • (A) 1
  • (B) 2
  • (C) 6
  • (D) 12
Show Answer

Answer: C – The balanced equation shows six water molecules produced per glucose molecule.

Anaerobic respiration and oxygen debt

Q21. Which description best fits anaerobic respiration?

  • (A) The movement of air in and out of the lungs without oxygen
  • (B) The chemical reactions in cells that release energy without using oxygen
  • (C) The diffusion of oxygen from the blood into muscle cells during vigorous exercise
  • (D) The breakdown of glucose using six oxygen molecules
Show Answer

Answer: B – Anaerobic respiration releases energy from nutrients without using oxygen.

Q22. Why does anaerobic respiration release much less energy per glucose molecule than aerobic respiration?

  • (A) The glucose molecule is only partly broken down
  • (B) The glucose molecule is broken down completely to water
  • (C) No glucose molecules are broken down at all
  • (D) The energy is used up making oxygen
Show Answer

Answer: A – Anaerobic respiration breaks glucose down only partly, so it releases much less energy per molecule.

Q23. What is the word equation for anaerobic respiration in yeast?

  • (A) Glucose + oxygen → carbon dioxide + water
  • (B) Glucose → lactic acid
  • (C) Carbon dioxide + water → glucose + oxygen
  • (D) Glucose → alcohol + carbon dioxide
Show Answer

Answer: D – In yeast, anaerobic respiration converts glucose into alcohol (ethanol) and carbon dioxide.

Q24. What is the balanced chemical equation for anaerobic respiration in yeast?

  • (A) C6H12O6 + 6O2 → 6CO2 + 6H2O
  • (B) C6H12O6 → 2C3H6O3
  • (C) C6H12O6 → 2C2H5OH + 2CO2
  • (D) 6CO2 + 6H2O → C6H12O6 + 6O2
Show Answer

Answer: C – One glucose molecule gives two molecules of ethanol and two molecules of carbon dioxide.

Q25. What is the word equation for anaerobic respiration in muscles during vigorous exercise?

  • (A) Glucose + oxygen → carbon dioxide + water
  • (B) Glucose → lactic acid
  • (C) Glucose → alcohol + carbon dioxide
  • (D) Lactic acid → glucose + oxygen
Show Answer

Answer: B – During vigorous exercise, muscle cells respire anaerobically and convert glucose into lactic acid.

Q26. During vigorous exercise, where does lactic acid build up?

  • (A) In the muscles and the blood
  • (B) In the lungs and the trachea
  • (C) In the stomach and the gut
  • (D) In the bones and the cartilage
Show Answer

Answer: A – Lactic acid builds up in the muscles and the blood during vigorous exercise, causing an oxygen debt.

Q27. What is meant by an oxygen debt after vigorous exercise?

  • (A) Oxygen that the lungs failed to take in during exercise
  • (B) Oxygen lost from the blood as sweat
  • (C) Oxygen used to build new muscle fibres
  • (D) Extra oxygen needed after exercise to break down the lactic acid built up
Show Answer

Answer: D – The oxygen debt is the extra oxygen required after exercise to deal with the lactic acid accumulated.

Q28. How does a fast heart rate after exercise help to remove the oxygen debt?

  • (A) It stops lactic acid leaving the muscles
  • (B) It cools the muscles so lactic acid dissolves
  • (C) It transports lactic acid in the blood from the muscles to the liver
  • (D) It converts lactic acid directly into glucose in the muscles
Show Answer

Answer: C – Continued fast heart rate carries lactic acid in the blood from the muscles to the liver.

Q29. Why does breathing stay deeper and faster for a while after vigorous exercise?

  • (A) To supply carbon dioxide for the breakdown of lactic acid in the liver
  • (B) To supply oxygen for the aerobic respiration of lactic acid
  • (C) To remove glucose from the blood as fast as possible
  • (D) To cool the lungs after exercise
Show Answer

Answer: B – Deeper, faster breathing supplies the oxygen needed for aerobic respiration of lactic acid.

Q30. Where, and by what process, is lactic acid finally broken down when the oxygen debt is repaid?

  • (A) In the liver, by aerobic respiration
  • (B) In the lungs, by gas exchange
  • (C) In the muscles, by anaerobic respiration
  • (D) In the blood, by diffusion
Show Answer

Answer: A – Lactic acid is broken down by aerobic respiration in the liver once enough oxygen is available.

Revise any questions you missed, especially the two anaerobic equations and the three steps that repay an oxygen debt, then retest yourself.