Explain why aerobic respiration releases more energy than anaerobic respiration.

WJEC GCSE Biology (Wales) — 1.2.1 Aerobic and anaerobic respiration · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Athletes training at high intensity may switch from aerobic to anaerobic respiration when oxygen supply to their muscles becomes insufficient.

Model answer (4 marks)

Aerobic respiration fully oxidises glucose to CO₂ and H₂O, releasing all the energy stored in the glucose molecule.
Anaerobic respiration only partially breaks down glucose; the glucose is not completely oxidised.
The products of anaerobic respiration, such as lactic acid, still contain chemical energy that is not released.
Aerobic respiration requires oxygen to carry out the complete oxidation, whereas anaerobic respiration does not use oxygen.

Examiner tips

  • Use the exact terms ‘fully oxidises’ and ‘partially breaks down’ to match the mark scheme.
  • Explain the role of oxygen in completing the oxidation process.
  • Show the energy difference by noting that lactic acid still stores energy.
  • Keep the answer concise – one sentence per point.

Mark scheme (4 marks)

  1. Aerobic respiration completely breaks down / fully oxidises glucose
  2. Anaerobic respiration only partially breaks down glucose / glucose is not completely broken down
  3. The products of anaerobic respiration (lactic acid) still contain chemical energy / energy remains stored in lactic acid
  4. Aerobic respiration requires oxygen (to fully oxidise glucose) whereas anaerobic respiration does not use oxygen

Key terms in this question

aerobic respiration · anaerobic respiration

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