Enzymes are proteins that act as biological catalysts. This means that they speed up useful reactions in the body, without being used up. Enzymes play an important role in cellular respiration and photosynthesis.
Find out more about cells and important reactions that take place within cells.
Enzymes are comprised of long chains of amino acids and have a very important feature called an active site. The active site is a region on an enzyme that has a particular shape. This shape is complementary to a specific substrate, which can be thought of as a reactant.
The specificity of the complementary pairs of enzymes and substrates means that different enzymes are necessary to catalyse different reactions. As the active site of one enzyme matches and joins up with its substrate, a reaction is catalysed and afterwards, the substrate can be considered a product.