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Enzymes Catalysts speed up the rate of a reaction without being used up A + B C, where A and B are reactants and C is the product. An example is MnO2 Enzymes are biological catalysts that are proteins (composed of amino acids). They are globular in shape. Names end in –ase— Catalase—2H2O2 2H2O + O2 Arginase—arginine + 2H2O urea + ornithine They work under physiological conditions (w/in the constraints of the cells and the organism) -- body temperature 37° C if temp. too low—slow reaction if temp. too high—denature enzyme -- physiological pH of 7 (too high, low denature enzyme) --- salt and metal concentration w/in cell --- substrate (a reactant converted to product by enzyme) concentration w/in cell Enzyme works by using an active site, which binds the substrate (the reactant) so that through catalysis a product is formed. It is not used up in the reaction. Active Site Enzyme Enzyme Substrate product Enzymes are very specific for a substrate—geometry/shape, charge, hydrophobicity. In above example, a substrate with a triangular or circular shape would not fit into the active site & therefore no product made. It also lowers the amount of energy required to covert the substrate to a product (as compared to an uncatalyzed reaction) Transition State Transition State S P G, free energy G, free energy Activation energy S Lower Activation Energy P Enzymes can be poisoned or inhibited so can’t convert substrate to product— Poisoning permanently alters active site—heavy metals (cyanide, arsenic) Inhibition is temporary by binding to active site—ether chloroform; uses as anesthesia. Today: Studying the enzyme catalase, which speeds up the following reaction-2H2O2 2 H2O + O2 (bubbles in vitro) I) Testing for catalase presence in various tissues (animal vs. plant) II) Effects of Temperature on catalase’s activity III) Effects of pH on catalase’s activity IV) Testing another feature of enzymes—what are we testing? Please help w/ clean up! Many thanks!