# A student is investigating a protein found in human hair. The protein has a specific three-dimensional shape that is essential for its function. Describe the structure of an amino acid and explain how a sequence of amino acids can fold into a three-dimensional protein shape, including why this shape is important for the protein's function.

> Eduqas A-Level Chemistry — 4.7 Amino acids, peptides and proteins · Describe and Explain · 5 marks

> Human hair contains a protein called keratin. Keratin's three-dimensional shape gives it structural properties that make hair strong and flexible.

## Mark scheme (5 marks)

1. An amino acid contains an amino group (-NH2)
2. An amino acid contains a carboxylic acid group (-COOH)
3. Different amino acids have different R groups / side chains, giving each amino acid different properties
4. Interactions between R groups / side chains in the chain of amino acids cause the protein to fold into a specific three-dimensional shape
5. The specific three-dimensional shape is essential for the protein's function, so if the shape changes the protein can no longer perform its function

## Key terms

- [amino acid](https://www.gradenine.co.uk/glossary/amino-acid)
- [three-dimensional shape](https://www.gradenine.co.uk/glossary/three-dimensional-shape)
- [protein](https://www.gradenine.co.uk/glossary/protein)

## Related

- [Revision notes for Eduqas A-Level Chemistry](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-student-is-investigating-a-protein-fe9053da) · Published by Druglandscape Ltd.