Metabolism is all chemical reactions taking place inside body cells of an organism. Catabolism is the breaking down of complex molecules into simpler ones. Anabolism is the building up of complex molecules from simpler ones. Catalyst is a substance that increases the rate of a chemical reaction and is not changed by the reaction. Enzymes are a protein that functions as biological catalyst speeding up chemical reactions in an organism. Enzymes are proteins in nature. Enzymes speed up biochemical reactions. Enzymes are effective in small quantities. The reactions enzymes catalyse are reversible. Enzymes are highly specific and can catalyse one type of reaction only. Enzymes will be affected by changes in temperatures and pH and can work effectively within a particular range of temperature and pH. High temperature and extreme pH can cause denaturing of enzymes.

We need enzymes because without them, most of the reactions that happen in cells would far too slow to allow life to go on. Enzymes biocatalysts needed for the reaction to start.

Substrate is the molecule that an enzyme acts on. Active site is the small area where the substrate binds to the enzyme. The active site is of particular 3D shape which must match the shapes of specific substrates for reaction to take place. If the shape of the active site of an enzyme molecule is changed, the substrate cannot fit into the active site of the enzyme molecule and it will not catalyse the reaction anymore. Substrates ,love faster at a higher temperature and hence the increasing chances for them to collide with the active site of the enzyme to form enzyme-substrate complex. At high temperature, bondings within the enzymes are broken.