What is an enzyme and explain the factors affecting it.

Enzymes are proteins. They are biological catalysts, meaning they increase the rate of reaction without being used up or changed. Different enzymes have different optimum temperatures and pHs, depending on their location in the body and function. As temperature increases, enzyme activity increases, as there is more kinetic energy and increased likelihood of the substance binding to the enzyme's active site. However, it reaches its optimum temperate at around 37C, where it then begins to decrease, and eventually denatures. Different enzymes have different optimum pHs and tend to still work in a small range around the optimum. Too great a change, though, causes the enzyme to denature. For example, pepsin has an optimum of around pH 2 as it is needed in the stomach and must withstand the acidic conditions. Pancreatic amylase, however, is needed in the small intestine, where conditions are basic (pH around 8). When an enzyme denatures, the bonds holding the protein chains together break, changes shape of enzyme and so the shape of the active site changes, meaning substance cannot bind to enzyme's active site and therefore cannot increase rate of reaction