# Describe how the structure of a leaf is adapted to allow carbon dioxide to reach the chloroplasts in the palisade mesophyll cells.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.5 Nutrition: flowering plants · Describe · 4 marks

## Mark scheme (4 marks)

1. Stomata (in the lower epidermis) allow carbon dioxide to enter the leaf by diffusion
2. Air spaces in the spongy mesophyll allow carbon dioxide to diffuse towards the palisade mesophyll
3. The large surface area of the leaf / spongy mesophyll cells increases the rate of diffusion of carbon dioxide
4. Chloroplasts are the site of photosynthesis and are present in the palisade mesophyll cells, so carbon dioxide is used there, maintaining a concentration gradient for continued diffusion

## Key terms

- [palisade mesophyll](https://www.gradenine.co.uk/glossary/palisade-mesophyll)
- [chloroplast](https://www.gradenine.co.uk/glossary/chloroplast)

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-the-structure-of-a-90163f53) · Published by Druglandscape Ltd.