Describe the role of physical digestion in the stomach and explain how this process benefits chemical digestion.

Cambridge International IGCSE Biology (0610) — 7.3 Mechanical digestion · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

The muscular walls of the stomach contract to mix, churn and grind the food.
This physical digestion breaks the food into smaller particles, increasing its surface area.
A larger surface area allows digestive enzymes to act on more of the food at once, raising the rate of enzyme action.
Consequently chemical digestion is faster and more efficient.

Examiner tips

Use the exact terms ‘mix, churn, grind’ and ‘increase surface area’. Show the causal link: physical digestion → larger surface area → faster enzyme action. Keep the answer concise, 4 points, no extra words.

Common mistakes

Using vague verbs such as ‘break down’ instead of ‘mix, churn, grind’. Omitting the link between increased surface area and enzyme efficiency. Writing more than four points or including irrelevant details.

Mark scheme (4 marks)

The muscular walls of the stomach contract to mix/churn/grind the food.
Physical digestion breaks food into smaller pieces, increasing its surface area.
A greater surface area allows enzymes to act on more of the food at once / increases the rate of enzyme action.
This speeds up / makes chemical digestion more efficient.

Key terms in this question

physical digestion · chemical digestion