Explain how physical digestion in the stomach helps chemical digestion to occur more efficiently.

Cambridge International IGCSE Biology (0610) — 7.3 Mechanical digestion · Explain · 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 food into smaller particles.
This increases the surface area of the food.
A greater surface area allows digestive enzymes to act on more of the food at once.
Thus chemical digestion proceeds faster, more efficiently and more completely.

Examiner tips

Use the exact phrase "muscular walls contract to mix, churn and grind" to hit the first point. Show the logical chain: mixing → increased surface area → more enzyme contact → faster digestion. Keep the answer to four short sentences to match the 4 marks.

Common mistakes

Using vague terms like "stomach works" instead of "muscular walls contract to mix, churn and grind". Omitting the link between increased surface area and enzyme action. Writing a long paragraph instead of four concise sentences.

Mark scheme (4 marks)

The muscular walls of the stomach contract to mix / churn / grind food into smaller pieces.
This increases the surface area of food (particles).
A greater surface area allows enzymes to act on / contact more of the food at once.
So chemical digestion / the rate of chemical digestion is faster / more efficient / more complete.

Key terms in this question

physical digestion · chemical digestion · stomach