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A Level Biology: Energy and respiration MCQs — Biology

29 multiple-choice questions on A Level Biology: Energy and respiration from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. An organism has an RQ of 0.7. It is most likely respiring

  1. carbohydrate
  2. anaerobically
  3. protein only
  4. lipid

Answer: D) lipid

Explanation: Lipids give RQ ≈ 0.7. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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2. A respirometer shows 24 mm³ O₂ used and 18 mm³ CO₂ released. The RQ is

  1. 1.0
  2. 0.75
  3. 1.33
  4. 0.67

Answer: B) 0.75

Explanation: 18 ÷ 24 = 0.75. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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3. Substrate-linked phosphorylation is

  1. phosphorylation of glucose in glycolysis
  2. ATP synthesis using light
  3. direct transfer of phosphate from a substrate to ADP
  4. ATP synthesis using a proton gradient

Answer: C) direct transfer of phosphate from a substrate to ADP

Explanation: Occurs in glycolysis and Krebs. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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4. Hydrolysis of ATP produces

  1. ADP and inorganic phosphate
  2. AMP and glucose
  3. NAD and phosphate
  4. ADP and oxygen

Answer: A) ADP and inorganic phosphate

Explanation: ATP + H₂O → ADP + Pi. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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5. The net gain of ATP from glycolysis per glucose is

  1. 4
  2. 0
  3. 36
  4. 2

Answer: D) 2

Explanation: 4 made, 2 used. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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6. Rice plants survive in flooded fields partly because they have

  1. leaves underwater
  2. no roots
  3. aerenchyma allowing oxygen to diffuse to the roots
  4. thick cuticles on roots

Answer: C) aerenchyma allowing oxygen to diffuse to the roots

Explanation: Air spaces carry O₂. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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7. Ethanol fermentation in yeast produces

  1. lactate
  2. oxygen and water
  3. lactate and CO₂
  4. ethanol and carbon dioxide

Answer: D) ethanol and carbon dioxide

Explanation: Pyruvate → ethanal + CO₂ → ethanol. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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8. Aerobic respiration yields much more ATP than anaerobic respiration because

  1. it produces lactate
  2. it uses more glucose
  3. glucose is completely oxidised via the Krebs cycle and oxidative phosphorylation
  4. it happens in the cytoplasm

Answer: C) glucose is completely oxidised via the Krebs cycle and oxidative phosphorylation

Explanation: Most ATP comes from oxidative phosphorylation. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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9. In glycolysis, glucose is first

  1. decarboxylated
  2. split into acetyl groups
  3. phosphorylated using ATP
  4. oxidised to pyruvate

Answer: C) phosphorylated using ATP

Explanation: Phosphorylation activates glucose. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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10. Where does glycolysis take place?

  1. Inner mitochondrial membrane
  2. Mitochondrial matrix
  3. Intermembrane space
  4. Cytoplasm

Answer: D) Cytoplasm

Explanation: Glycolysis is cytoplasmic. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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11. How many molecules of CO₂ are released per turn of the Krebs cycle?

  1. 1
  2. 6
  3. 3
  4. 2

Answer: D) 2

Explanation: Two decarboxylations per turn. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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12. In the DCPIP investigation of yeast respiration, DCPIP

  1. absorbs CO₂
  2. produces oxygen
  3. accepts hydrogen and turns from blue to colourless
  4. turns blue when respiration occurs

Answer: C) accepts hydrogen and turns from blue to colourless

Explanation: Redox indicator. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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13. The final electron acceptor in oxidative phosphorylation is

  1. carbon dioxide
  2. NAD
  3. oxygen
  4. FAD

Answer: C) oxygen

Explanation: Oxygen forms water. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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14. The RQ for carbohydrate respiration is

  1. 0.9
  2. 0.7
  3. 1.0
  4. 1.5

Answer: C) 1.0

Explanation: Equal moles of CO₂ and O₂. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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15. Why is a layer of oil placed over yeast suspension in a methylene blue experiment?

  1. To feed the yeast
  2. To absorb CO₂
  3. To keep the temperature constant
  4. To prevent oxygen reoxidising the dye

Answer: D) To prevent oxygen reoxidising the dye

Explanation: Oxygen would recolour the dye. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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16. ATP is described as the universal energy currency because

  1. it cannot be hydrolysed
  2. it is only found in muscle cells
  3. it stores energy for long periods
  4. it is used to transfer energy in all cells

Answer: D) it is used to transfer energy in all cells

Explanation: All organisms use ATP. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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17. In anaerobic respiration in mammals, pyruvate is converted to lactate in order to

  1. produce more ATP directly
  2. remove oxygen
  3. make CO₂
  4. regenerate NAD so glycolysis can continue

Answer: D) regenerate NAD so glycolysis can continue

Explanation: NAD must be reoxidised. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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18. Why is a control tube with glass beads used in a respirometer?

  1. To measure RQ directly
  2. To correct for changes in temperature and pressure
  3. To supply oxygen
  4. To absorb CO₂

Answer: B) To correct for changes in temperature and pressure

Explanation: It compensates for physical changes. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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19. The link reaction converts pyruvate into

  1. lactate
  2. acetyl coenzyme A and carbon dioxide
  3. citrate
  4. oxaloacetate

Answer: B) acetyl coenzyme A and carbon dioxide

Explanation: Decarboxylation and dehydrogenation. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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20. Fructose 1,6-bisphosphate splits into

  1. acetyl CoA
  2. two pyruvates
  3. citrate
  4. two triose phosphates

Answer: D) two triose phosphates

Explanation: 6C → two 3C. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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21. Protons return to the matrix through

  1. electron carriers
  2. the outer membrane
  3. coenzyme A
  4. ATP synthase

Answer: D) ATP synthase

Explanation: Facilitated diffusion through ATP synthase drives ATP synthesis. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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22. In the Krebs cycle, acetyl (2C) combines with oxaloacetate (4C) to form

  1. pyruvate (3C)
  2. citrate (6C)
  3. glucose
  4. triose phosphate

Answer: B) citrate (6C)

Explanation: 2C + 4C = 6C citrate. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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23. Which is an anabolic reaction requiring energy?

  1. Protein synthesis
  2. Diffusion
  3. Glycolysis
  4. Hydrolysis of starch

Answer: A) Protein synthesis

Explanation: Building macromolecules needs ATP. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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24. Energy released as electrons pass along the electron transport chain is used to

  1. reduce oxygen directly to ATP
  2. make glucose
  3. split water
  4. pump protons into the intermembrane space

Answer: D) pump protons into the intermembrane space

Explanation: Protons are pumped to create a gradient. AS & A Level Biology · Topic 12 Energy and Respiration · 12.2 Respiration

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25. Lipids release more energy per gram than carbohydrates because they contain

  1. more oxygen atoms
  2. more hydrogen atoms per molecule
  3. more nitrogen
  4. fewer carbon atoms

Answer: B) more hydrogen atoms per molecule

Explanation: More H means more reduced NAD and ATP. AS & A Level Biology · Topic 12 Energy and Respiration · 12.1 Energy

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