Explain how the structure of a leaf is adapted to allow efficient photosynthesis.

WJEC GCSE Biology (Wales) — 1.5.1 Plant structure and function · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

A leaf is thin and flat, so light can reach the cells inside.
The palisade mesophyll cells are densely packed with chloroplasts, which absorb light for photosynthesis.
Stomata on the leaf surface allow carbon dioxide to enter the leaf.
The spongy mesophyll layer contains air spaces that enable CO₂ and other gases to diffuse to the cells.

Examiner tips

Use the exact terms: leaf, thin, flat, palisade mesophyll, chloroplasts, stomata, spongy mesophyll, air spaces. Show the causal link: structure → function → efficient photosynthesis. Keep each point short and to the point to hit the 4 marks.

Common mistakes

Confusing palisade with spongy mesophyll. Forgetting to mention stomata. Using vague phrases like "good for photosynthesis" without detail.

Mark scheme (4 marks)

The leaf is thin / flat, which allows light to penetrate to the cells inside
The palisade mesophyll cells are packed with chloroplasts, which absorb light for photosynthesis
Stomata allow carbon dioxide to enter the leaf (for photosynthesis)
The spongy mesophyll layer has air spaces that allow carbon dioxide / gases to diffuse to the cells

Key terms in this question

photosynthesis