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  • Created by: IsobelW
  • Created on: 01-12-15 13:10


Enzymes are biological catalysts - protein molecules that speed up chemical reactions. They catalyse chemical reactions in living cells such as:

  • Respiration.
  • Photosynthesis.
  • Proteinsynthesis

Active sites

The shape of an enzyme determines how it works. Enzymes have active sites that substrate molecules (the substances involved in the chemiclal reaction) fit into when a reaction happens.

The active site has to be the right shape for the substrate molecules to fit into. This means that enzymes have a high specificity for their substrate - a particular type of enzyme will only work with one or a smaller number of substrates.

The mechanism involved is called the 'lock and key' mechanism. Just as a lock will only accept one key, an enzyme will only accept one substrate.

Enzymes and temperature

At low temperatures, enzyme reactions are slow. They speed up as


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