Explain why the upper epidermis and palisade mesophyll are both important for efficient photosynthesis in a leaf.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The upper epidermis is transparent, so light can pass through it and reach the palisade mesophyll. The palisade mesophyll lies just below the upper epidermis, where most of the light is received. Its cells contain many chloroplasts, which have chlorophyll to absorb light energy for photosynthesis. Because the upper epidermis lacks chloroplasts, it does not block or reduce the light that reaches the palisade mesophyll.
Examiner tips
- Use the word ‘transparent’ for the upper epidermis; examiners look for this term.
- Mention that palisade cells are rich in chloroplasts and are positioned to receive light.
- Show the link between light passage and chlorophyll absorption.
- Keep the answer concise – 4 points only.
Mark scheme (4 marks)
- The upper epidermis is transparent, allowing light to pass through to the palisade mesophyll.
- The palisade mesophyll is positioned near the top of the leaf where most light is received.
- Palisade mesophyll cells contain many chloroplasts, which contain chlorophyll to absorb light energy for photosynthesis.
- The upper epidermis does not contain chloroplasts, so it does not block or reduce the light available to the palisade mesophyll.
Key terms in this question
upper epidermis · palisade mesophyll
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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