Enzyme action

Chemical reactions take place throughout living organisms. Many of these metabolic reactions would be too slow to sustain life without enzymes. Enzymes are proteins that increase the rates of these reactions.

An enzyme is a biological catalyst: it speeds up a reaction without being changed by it. This means the same enzyme can be used again.

How an enzyme acts on its substrate

The substance an enzyme acts on is called its substrate. The enzyme has a region called the active site, whose shape is complementary to the substrate. This allows the substrate to bind to the active site.

The enzyme catalyses the reaction, forming products from the substrate. The products are then released from the active site. The enzyme remains unchanged and can bind another substrate molecule and catalyse the reaction again.