# A scientist is investigating molecules found in cell membranes and in the adipose tissue of a deep-diving whale. Describe the structure of a lipid molecule and explain why the same type of molecule can serve two very different functions in the whale's body.

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

> Lipids are found throughout living organisms. In whales, lipids are a major component of cell membranes and are also stored in thick layers of adipose tissue beneath the skin.

## Mark scheme (5 marks)

1. A lipid is made from one glycerol molecule joined to three fatty acid molecules
2. Lipids contain carbon, hydrogen, and oxygen
3. The adipose tissue stores lipids as an energy reserve / lipids release energy when broken down
4. The layer of adipose tissue also acts as insulation, reducing heat loss to the cold water
5. Lipids are a component of cell membranes / form the phospholipid bilayer of membranes

## Key terms

- [lipid](https://www.gradenine.co.uk/glossary/lipid)
- [adipose tissue](https://www.gradenine.co.uk/glossary/adipose-tissue)
- [cell membrane](https://www.gradenine.co.uk/glossary/cell-membrane)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/a-scientist-is-investigating-molecules-found-72b88c90) · Published by Druglandscape Ltd.