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Unformatted text preview: Enzymes The chemical reactions in all cells of living things operate in the presence of biological catalysts called enzymes. Because a particular enzyme catalyzes only one reaction, there are thousands of different enzymes in a cell catalyzing thousands of different chemical reactions. The substance changed or acted on by an enzyme is its substrate. The products of a chemical reaction catalyzed by an enzyme are end products. All enzymes are composed of proteins. (Proteins are chains of amino acids.) When an enzyme functions, a key portion of the enzyme called the active site interacts with the substrate. The active site closely matches the molecular configuration of the substrate. After this interaction has taken place, a change in shape in the active site places a physical stress on the substrate. This physical stress aids the alteration of the substrate and produces the end products. During the time the active stress aids the alteration of the substrate and produces the end products....
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- Fall '07