# Explain how the primary structure of a protein determines its three-dimensional shape and, therefore, its function.

> IB DP Biology Standard Level (2023 syllabus) — B1.2 Proteins · Explain · 4 marks

## Mark scheme (4 marks)

1. Primary structure is the specific sequence of amino acids in a polypeptide chain
2. The R groups of amino acids interact with each other (e.g. hydrogen bonds, ionic bonds, disulfide bonds, hydrophobic interactions) to produce secondary and tertiary folding
3. The sequence of amino acids (primary structure) therefore dictates the final three-dimensional (tertiary) shape of the protein
4. The specific three-dimensional shape produces a specific active site / binding site, so the protein can only interact with complementary molecules and carry out its particular function

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-primary-structure-of-05a8117a) · Published by Druglandscape Ltd.