The majority of the reactions that occur in living organisms atomic number 18 enzyme-controlled. Without them, the prise of the reactions would be so slow as to cause serious, if not fatal, damage. Without enzymes toxins would soon build up and the supply of respiratory substrate would decrease. Enzymes are proteins and thus have a specific mildew. They are in that locationfore specific in the reactions that they catalyse - one enzyme volition react with atoms of one substrate. The settle of the reaction occurs in an sphere of influence on the surface of the protein c everyed the active come out. Since the active site for all molecules of one enzyme will be made up of the analogous arrangement of amino group acids, it has a highly specific shape. Generally, there is only one active site on each enzyme molecule and only one type of substrate molecule will fit into it. Chymotrypsin and trypsin both catalyse the hydrolysis of peptide bonds but due(p) to their shapes, the active site of chymotrypsin only splits bonds after an aromatic amino acid (one containing a ring of atoms) whereas trypsin only splits bonds after a basic or straight chain amino acid. This specificity leads to the pursue and key hypothesis. However, it has been discovered that competitors for an active site (similar in shape to the substrate) could fit even though they are larger than the substrate.
This sum that the substrate and active site are a precise flexible. This has lead to the induced fit model.
Induced fit model
When the enzyme and substrate normal a complex, structural changes occur so that the active site fits precisely around the substrate (the substrate induces the active site to change shape). The reaction will take place and the product, universe a different shape to the substrate, moves away from the active site.
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