enzymes

Enzymes 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 a temporary association with the molecules that are reacting. During this process, the catalyst itself is not permanently altered in the process, and so it can be used over and over again. …

…change, that prevents the active site from binding to the proper substrate. An allosteric change could be either a negative modulator or a positive effector. There’s also cooperativity. This is the binding at an active site that makes the others more reactive. An example to this is hemoglobin. Co-enzymes are also factors of enzymes. These are heme-groups or prosthetic groups that bind to the enzymes loosely as part of the reactions, such as vitamins.