# A leaf is adapted for efficient gas exchange. Describe the features of a leaf that make it well-adapted for gas exchange, and explain how each feature helps gases to be exchanged efficiently.

> Eduqas A-Level Biology — 2.2 Adaptations for gas exchange · Describe · 5 marks

## Mark scheme (5 marks)

1. Stomata (pores) in the lower epidermis allow gases to diffuse into and out of the leaf
2. The spongy mesophyll has air spaces which increase the surface area for gas exchange / allow fast diffusion of gases inside the leaf
3. The cells forming the exchange surface are thin / have a short diffusion distance, so gases diffuse across quickly
4. The moist surface of cells lining the air spaces allows gases to dissolve before diffusing across the membrane
5. A large concentration gradient is maintained (e.g. carbon dioxide is used up in photosynthesis / oxygen is used in respiration) which increases the rate of diffusion

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-leaf-is-adapted-for-efficient-a535d808) · Published by Druglandscape Ltd.