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ENZYMES

ENZYMES. Biological Catalysts. ENZYMES are important proteins. Many chemical reactions in living cells (and organisms) are regulated by ENZYMES Enzymes are globular proteins in living systems that mediate metabolic reactions

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ENZYMES

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  1. ENZYMES Biological Catalysts

  2. ENZYMES are important proteins • Many chemical reactions in living cells (and organisms) are regulated by ENZYMES • Enzymes are globular proteins in living systems that mediate metabolic reactions • Metabolism:  the series of energy exchanges and chemical reactions that occur in living systems (cells, organisms) • catabolic activities = breakdown of larger molecules into smaller; AB ==> A + B • anabolic activities = synthesis of larger molecules from smaller ones;  A + B ==> AB

  3. Energy and Chemical Reactions • Exergonic rxn’s = release energy (products have less chemical energy than reactants) ex: AB + CD  AC + DB + energy

  4. Energy and Chemical Reactions • Endergonicrxn’s = absorb energy (products have more chemical energy than reactants) ex: AB + CD + energy  AC + DB • Catalysts: reduce the amount of activation energy that is needed to start the rxn. See Figure 2-7 in your book. Activation energy: energy added to reactants to "jumpstart" the rxn

  5. Enzymes act as catalysts (push, or speed up, chemical reactions) • Enzymes lower the ACTIVATION ENERGY of reactions (ex: heat required) needed to enable chemical bonds to form or break • Reactions that involve enzymes occur more easily than they normally would.

  6. Each Enzyme acts upon a specificsubstrate (there are thousands of different enzymes in the body to mediate thousands of different reactions) • Enzymes have an active site, to fit with their substrate in a "lock-and-key" fashion • Sometimes, to get a good "fit", enzymes require a vitamin or mineral to fit into the active site: COENZYME • "Induced Fit Hypothesis" a change in the shape of an enzyme’s active site may occur, which allows it to bind more effectively to its substrate

  7. Enzymes mediate the reaction in the substrate but do not take part in the reaction themselves, so enzymes can be re-used again and again • Enzymes can be deactivated (DENATURED) when their 3-D active site is warped by heat or drastic pH changes (acid) • Some classes of enzymes:  • Proteases • Lipases • Amylases (sucrase, lactase, etc.) • most enzyme names end in    -ane     or    -ase   suffix, and most are named after the substrate upon which they act

  8. LAB Enzyme: catalase Reaction it catalyzes:

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