An enzyme is a protein that speeds up a chemical reaction or catalyzes a reaction. More than 2,000 enzymes are known. Enzymes are crucial because without them, reaction rates would be too slow to sustain life. For example, the breakdown of food involves various enzymes which catalyze proteins and carbohydrates. Molecules that are affected by enzymes are called substrates.
Substrates bind to the surface of the enzyme called an active site.
Once they bind, an enzyme-substrate complex is formed, which in turn produces a product and the unchanged enzyme. An inhibitor is any compound which causes a decrease in the catalytic rate. There are two types of reversible inhibitors. Therefore, it can block the binding of a substrate. Another type of reversible inhibition is called noncompetitive inhibition.