# A nutritionist is comparing the biological molecules found in a chicken breast and a stick of butter. Explain how the structures and functions of proteins and lipids differ, and state one element found in proteins that is not found in lipids.

> Pearson Edexcel A-Level Biology A (9BI0) — Topic 1 Biological Molecules · Explain · 5 marks

> Proteins and lipids are two important biological molecules found in food. Both are made up of smaller building-block molecules and play essential roles in the body.

## Mark scheme (5 marks)

1. Proteins are made from amino acids (monomers / building blocks)
2. Lipids are made from fatty acids and glycerol
3. Proteins have a variety of functions such as growth, repair, or making enzymes / antibodies / hormones
4. Lipids function as an energy store / source of insulation / waterproofing
5. Nitrogen (accept: sulfur) is found in proteins but not in lipids

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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/a-nutritionist-is-comparing-the-biological-a24c1d88) · Published by Druglandscape Ltd.