How enzymes work

How enzymes workSpec 1.7

Enzymes are proteins that act as biological catalysts. A catalyst speeds up a reaction without being used up. Each enzyme has a region called the active site, which has a particular shape.

The molecule an enzyme acts on is called the substrate. The substrate has a shape that is complementary to the active site, so it fits in, like a key in a lock. This is called the lock and key model.

1. The substrate collides with the active site of the enzyme.
2. The substrate fits into the active site, forming an enzyme-substrate complex.
3. The reaction takes place at the active site.
4. The product or products leave the active site and the enzyme is free to be used again.

Enzymes are specific. Only a substrate with a shape that fits the active site can bind to it, so each enzyme catalyses only one type of reaction.

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