Enzyme
Proteins (and in rare cases RNA) that catalyze metabolic reactions.
Active Site
A uniquely shaped pocket of the enzyme, where the substrate transiently binds with the enzyme as it is converted into an end product.
End Product
What the substrate is converted into by the enzyme.
Substrate or Reactant
The molecule to be metabolized by the enzyme.
Inhibitor
A molecule that binds to an enzyme and decreases it’s activity.