# Explain how the structural features of waxes make them suitable for their role in reducing water loss from the surfaces of leaves and insect cuticles.

> IB DP Biology Higher Level (2023 syllabus) — B1.1 Carbohydrates and lipids · Explain · 4 marks

## Mark scheme (4 marks)

1. Waxes are esters formed from long-chain fatty acids and long-chain alcohols (rather than glycerol), giving a large non-polar / hydrophobic molecule.
2. The long, saturated hydrocarbon chains allow wax molecules to pack tightly together, forming a solid / semi-solid layer at biological temperatures.
3. The hydrophobic nature of wax means water molecules cannot form hydrogen bonds with it and are therefore repelled / cannot pass through the wax layer.
4. The solid, continuous wax layer therefore acts as a barrier that greatly reduces evaporation / transpiration of water from the surface, limiting water loss.

## Key terms

- [wax](https://www.gradenine.co.uk/glossary/wax)
- [cuticle](https://www.gradenine.co.uk/glossary/cuticle)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structural-features-of-209e64ac) · Published by Druglandscape Ltd.