Explain why aerobic respiration releases more energy than anaerobic respiration from the same amount of glucose.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Cells can release energy from glucose using either aerobic or anaerobic respiration, but the two processes do not release the same amount of energy.
Model answer (4 marks)
Aerobic respiration fully oxidises glucose to CO₂ and H₂O, so all the chemical bonds are broken and the energy stored in the glucose is released as ATP.
In anaerobic respiration glucose is only partially broken down; the end‑products (lactic acid in animals, ethanol and CO₂ in yeast/plants) still contain some of the original chemical energy.
Because the end‑products still contain energy, less of the glucose energy is transferred to the cell as ATP.
Hence aerobic respiration releases more energy than anaerobic respiration from the same amount of glucose.
In anaerobic respiration glucose is only partially broken down; the end‑products (lactic acid in animals, ethanol and CO₂ in yeast/plants) still contain some of the original chemical energy.
Because the end‑products still contain energy, less of the glucose energy is transferred to the cell as ATP.
Hence aerobic respiration releases more energy than anaerobic respiration from the same amount of glucose.
Examiner tips
- Use the terms "fully oxidised" and "partially broken down". Show the link between the end‑products and the amount of energy released. Keep the answer short and to the point to fit the 4 marks.
Common mistakes
- Confusing the products of aerobic and anaerobic respiration. Using vague phrases like "more energy" without explaining why. Leaving out the fact that anaerobic products still contain energy.
Mark scheme (4 marks)
- Aerobic respiration completely breaks down / fully oxidises glucose
- Anaerobic respiration only partially breaks down glucose
- Anaerobic respiration produces lactic acid (in animals) / ethanol and carbon dioxide (in yeast/plants) as products still containing energy
- Therefore less energy is transferred / released to the cell during anaerobic respiration
Key terms in this question
aerobic respiration · anaerobic respiration · glucose
Related
- All Eduqas GCSE Biology revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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