# Explain why a thick layer of lipid stored beneath the skin is important for a polar bear surviving in Arctic conditions. Give three reasons in your answer.

> AQA A-Level Biology (7402) — 3.1.3 Lipids · Explain · 5 marks

> Polar bears live in the Arctic, where temperatures can fall below −40 °C. They rely on reserves stored in their bodies to survive long periods without food.

## Mark scheme (5 marks)

1. Lipid acts as an energy store / releases energy when food is scarce
2. Lipid contains more energy per gram than carbohydrate (so is a more efficient store)
3. Lipid acts as an insulator / reduces heat loss to the environment
4. Lipid is insoluble in water / does not dissolve in body fluids
5. Lipid molecules are made of glycerol and fatty acids (correct structural reference linking to high energy content or storage)

## Key terms

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

## Related

- [Revision notes for AQA A-Level Biology (7402)](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-why-a-thick-layer-of-242eb00f) · Published by Druglandscape Ltd.