Explain why aerobic respiration is described as an exothermic reaction, and state where in the cell aerobic respiration takes place.

OCR GCSE Biology A: Gateway Science (J247) — B1.3 Respiration · Explain · 4 marks · View as Markdown

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

During exercise, a student's muscles require a large and continuous supply of energy. The student's body relies mainly on aerobic respiration to meet this demand.

Model answer (4 marks)

Aerobic respiration releases energy from glucose.
An exothermic reaction is one that releases energy to the surroundings (as heat or ATP).
Therefore aerobic respiration is exothermic because it releases energy.
Aerobic respiration takes place in the mitochondria.

Examiner tips

  • Use the word "releases" to link energy release to exothermic. Mention glucose as the source of energy. State the organelle (mitochondria) clearly.
  • common_mistakes
  • :
  • Saying "it produces heat" without linking to energy release. Omitting the mitochondria as the site of respiration.

Mark scheme (4 marks)

  1. Aerobic respiration releases energy (from glucose)
  2. An exothermic reaction is one that releases energy (as heat/ATP/to the surroundings)
  3. Therefore aerobic respiration is exothermic because it releases energy (linking the two points together)
  4. Aerobic respiration takes place in the mitochondria

Key terms in this question

aerobic respiration · exothermic reaction

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