# A student claims that lipids and carbohydrates both contain carbon, hydrogen and oxygen, so they must have the same properties and functions in the body. Evaluate this claim.

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

## Mark scheme (5 marks)

1. The claim is partially correct — both lipids and carbohydrates contain carbon, hydrogen and oxygen
2. Lipids have a much higher ratio of hydrogen to oxygen compared to carbohydrates
3. Lipids are made of glycerol and fatty acids, whereas carbohydrates are made of sugar (glucose/monosaccharide) units
4. Lipids release more energy per gram than carbohydrates, so they are a more efficient energy store
5. Lipids have functions that carbohydrates do not, such as insulation or forming cell membranes

## Key terms

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

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Evaluate" 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-student-claims-that-lipids-and-de09adcb) · Published by Druglandscape Ltd.