# Active site and induced fit

The active site is the pocket where the substrate binds. In induced fit, the enzyme changes shape slightly around the substrate for a tighter grip.

Biology (university) · Part 02: Enzymes and energy · Card 6 of 9 · Last updated 2026-10-19

## Analogy

A glove that moulds to your hand as you put it on.

## In practice

Hexokinase closes around glucose when it binds, which keeps water out and helps transfer a phosphate.

## Practice

### Flashcards

- **What is induced fit?** The enzyme changes shape slightly when the substrate binds, giving a tighter fit.

## Questions people ask

### What is the difference between lock-and-key and induced fit?

Lock-and-key pictured a rigid enzyme with a perfectly matching shape. Induced fit is the better model: the enzyme and substrate both adjust as they meet, so the grip tightens as the reaction begins. This helps the enzyme strain the substrate toward the transition state.

### What are cofactors and coenzymes?

Cofactors are non-protein helpers that many enzymes need, such as zinc or magnesium ions. Coenzymes are organic helpers, often made from vitamins, such as NAD+. They carry small groups or electrons between reactions. That is one reason that vitamin shortages can cause disease.

## Related concepts

- [Enzyme](https://studyvisually.com/learn/science/biology-university/biology-university-part-2/biology-university-part-2-concept-5)
- [Enzyme kinetics](https://studyvisually.com/learn/science/biology-university/biology-university-part-2/biology-university-part-2-concept-7)
- [Enzyme inhibition](https://studyvisually.com/learn/science/biology-university/biology-university-part-2/biology-university-part-2-concept-8)
- [Feedback inhibition](https://studyvisually.com/learn/science/biology-university/biology-university-part-2/biology-university-part-2-concept-9)

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