# Explain how the induced fit model accounts for the specificity and catalytic activity of enzymes.

> IB DP Biology Higher Level (2023 syllabus) — C1.1 Enzymes and metabolism · Explain · 4 marks

## Mark scheme (4 marks)

1. The active site of an enzyme is not a rigid, pre-formed complementary shape but is flexible/dynamic, changing conformation upon substrate binding.
2. Interaction between the substrate and R-groups/amino acid residues of the active site induces a conformational change that optimally positions catalytic residues around the substrate.
3. The conformational change creates mechanical strain/distortion in the substrate's bonds, lowering the activation energy of the reaction.
4. Specificity is explained because only a substrate with the correct molecular geometry/complementary chemical properties can trigger the precise conformational change, so non-complementary molecules cannot induce a productive fit.

## Key terms

- [induced fit model](https://www.gradenine.co.uk/glossary/induced-fit-model)
- [specificity](https://www.gradenine.co.uk/glossary/specificity)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-induced-fit-model-8b6c8b79) · Published by Druglandscape Ltd.