Enzyme - Biological catalyst, usually a protein, that speeds up a chemical reaction

Substrate - A substance that is recognized by and binds to an enzyme

Active site - A pocket or groove in an enzyme that binds its substrate

Induced-fit model - A model of enzyme activity that describes how an enzyme changes shape to better accommodate a substrate

Cofactor - a non-protein group that binds to an enzyme and is essential for catalytic activity

Coenzyme - An organic molecule that acts as a cofactor of an enzyme

Competitive inhibition - A situation in which a competitor substance binds to a normal substrate binding site to block enzyme activity

Non-Competitive inhibition - A situation in which molecules bind to an enzyme at a site that is not the active site, thus blocking enzyme activity

Allosteric site - A binding site on an enzyme that binds regulatory molecules

Allosteric regulation - The regulation of one site of a protein by binding to another site on the same protein

Feedback Inhibition - The regulation of a pathway by one of the products of this pathway