Carbon dioxide is produced during respiration in muscle cells and diffuses into the blood. Describe the factors that determine how quickly carbon dioxide diffuses out of a muscle cell.

Cambridge International IGCSE Biology (0610) — 3.1 Diffusion · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

A greater concentration gradient increases the rate of diffusion
A larger surface area of the cell membrane increases the rate of diffusion
A shorter diffusion distance increases the rate of diffusion
Higher temperature increases the rate of diffusion

Examiner tips

  • Use the exact wording from the mark scheme; list each factor clearly
  • Show the cause–effect relationship (e.g. ‘A greater concentration gradient …’).

Common mistakes

  • Mixing up diffusion with active transport; forgetting to mention temperature; omitting the concentration gradient.

Mark scheme (4 marks)

  1. A greater concentration gradient increases the rate of diffusion
  2. A larger surface area of the cell membrane increases the rate of diffusion
  3. A shorter diffusion distance increases the rate of diffusion
  4. Higher temperature increases the rate of diffusion

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