Describe how the structure of a leaf is adapted to allow photosynthesis to occur efficiently. In your answer, refer to the palisade mesophyll, the upper epidermis and the stomata.

Cambridge International IGCSE Biology (0610) — 6.1 Photosynthesis · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

Palisade mesophyll cells are packed with chloroplasts, so they can absorb light energy efficiently.
They are located just below the upper epidermis, where most light reaches the leaf.
The upper epidermis is made of transparent cells, allowing light to pass through to the palisade mesophyll.
Stomata on the leaf surface let CO₂ diffuse into the leaf for use in photosynthesis.

Examiner tips

  • Use the word ‘packed’ or ‘rich in’ for chloroplasts. Mention the position of palisade cells relative to the upper epidermis. State that the upper epidermis is transparent. Explain that stomata allow CO₂ entry by diffusion.

Common mistakes

  • Saying the palisade mesophyll is ‘below’ the upper epidermis without noting its position near the top. Forgetting to mention that the upper epidermis is transparent. Confusing stomata with other leaf structures such as trichomes.

Mark scheme (4 marks)

  1. Palisade mesophyll contains many chloroplasts to absorb light energy for photosynthesis
  2. Palisade mesophyll is positioned near the top of the leaf where most light reaches it
  3. Upper epidermis cells are transparent, allowing light to pass through to the palisade mesophyll
  4. Stomata allow carbon dioxide to enter the leaf by diffusion for use in photosynthesis

Key terms in this question

palisade mesophyll · upper epidermis · stomata · photosynthesis

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