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. Because of catalysts, cells are able to carry out chemical reactions at a great speed and at comparative low temperatures. Almost 2, 000 different enzymes are now known, each of them capable of catalyzing a specific chemical reaction.
The molecule (s) on which an enzyme acts is known as its substrate. For example, sucrose is the substrate for the enzyme sucrase. Enzymes have specific structures that only its specific substrate will fit into. The polypeptide chains of an enzyme are folded in such way that they form a grove or pocket on the surface. The substrate fits in to this grove, 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 enzymes 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 enzymes 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 enzyme.
The Essay on Enzyme-controlled reaction
... collision between the enzymes and substrate and so increasing the rate of reaction. At these higher temperatures the active site of the enzyme is actually fairly ... group are non-protein molecules. They are covalently (strongly) bonded to the enzyme and must be there for the enzyme to function properly. ...
In non-competitive inhibition the binding of a non-competitive inhibitor to another site on the enzyme induces an allosteric change, or conformational 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.
