# Describe the role of stomata and the spongy mesophyll layer in gas exchange in a flowering plant.

> Pearson Edexcel International GCSE Biology (4BI1) — 2.8 Gas exchange: flowering plants · Describe · 4 marks

## Mark scheme (4 marks)

1. Stomata are pores (in the lower epidermis) through which gases enter and leave the leaf
2. Carbon dioxide diffuses into the leaf (down a concentration gradient) and oxygen diffuses out during photosynthesis / the reverse occurs during respiration
3. The spongy mesophyll contains large air spaces that allow gases to circulate / diffuse throughout the leaf
4. The large surface area of spongy mesophyll cells increases the area over which gas exchange (diffusion) can occur

## Key terms

- [stomata](https://www.gradenine.co.uk/glossary/stomata)
- [spongy mesophyll](https://www.gradenine.co.uk/glossary/spongy-mesophyll)

## 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-the-role-of-stomata-and-0c176178) · Published by Druglandscape Ltd.