Beginning of Essay
are proteins, composed of polypeptide chains and non-protein groups. Their function is to help with the reactions of many cells and molecules by serving as catalysts. A catalyst is a substance that allows the activation energy required for a reaction by forming ....

Middle of Essay
.... which is the site of reactions catalyzed by the enzyme, or active site. Recent studies of enzyme structure have suggested that the active site is flexible. The binding between and substrate appears to alter the shape of the enzyme. This induces a close fit between the active site and the substrate. It is also believed that this may put some strain on the substrate molecule facilitating the reaction. Another characteristics of are competitive inhibition and non-competitive inhibition. Competitive inhibition is the binding of a competitive molecule to the active site of the enzyme. This prevents the proper substrate from reacting with the enzy ....