# Explain why a protein loses its function when it is denatured.

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

## Mark scheme (4 marks)

1. Denaturation involves the breaking of bonds (hydrogen bonds / ionic bonds / disulfide bonds) that maintain the tertiary structure of the protein.
2. The tertiary (three-dimensional) shape / conformation of the protein is altered / lost.
3. The active site (or binding site) changes shape, so substrate / ligand can no longer fit / bind.
4. Function depends on the specific shape of the protein, so any change in shape prevents the protein from carrying out its role (e.g., catalysis, transport, signalling).

## Related

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