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Enzymes

Enzymes. Energetics. First Law of Thermodynamics – energy cannot be created or destroyed, it can only change forms . Second Law of Thermodynamics – (potential energy transformation into heat or other random molecular motion) Entropy (disorder) is continuously increasing.

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Enzymes

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  1. Enzymes

  2. Energetics • First Law of Thermodynamics – energy cannot be created or destroyed, it can only change forms

  3. Second Law of Thermodynamics – (potential energy transformation into heat or other random molecular motion) Entropy (disorder) is continuously increasing

  4. Catabolism – metabolic reactions that result in the breakdown of complex molecules into simple compounds, usually with the release of energy • Anabolism – Those chemical reactions involved in biosynthesis, usually requires the input of energy

  5. Free Energy • The amount of energy available to make or break chemical bonds (the amount of energy available to do work)

  6. Endergonic reactions – those chemical reactions that require an input of energy and do not proceed spontaneously. • productscontain more free energythan the reactants

  7. Exergonic reactions – those chemical reactions that proceed spontaneously • products contain less free energy than the reactants; energy is given off as heat. • Most require an input of energy to get started (activation energy)

  8. The amount of activation energy can be lowered using catalysts (substances that lower the amount of activation energy by stressing chemical bonds) • Ex: enzymes

  9. Enzymes • Enzymes (biological catalysts) are very specific types of functional proteins. • Act as catalysts in biological systems (help mediate chemical activity)

  10. Enzymes are “substrate specific”; one enzyme for each type of substrate • Enzymes end in “ase” • Enzymes are reusable

  11. Enzymes work by lowering the activation energy needed for chemical reactions to occur • Enzymes have an active site to which the substrate bonds forming the “enzyme-substrate complex. Any change in this site will render the enzyme inactive

  12. Induced Fit

  13. Operate in a very narrow pH, temperature and ionic range. • varies from enzyme to enzyme; ex: enzymes in stomach vs. enzymes in blood; enzymes of the bacteria in thermal vents of Pacific vs. most other bacterial enzymes

  14. Factors Affecting Enzyme Activity: • Temperature: Optimum vs. Denaturation • pH • Salinity

  15. Inhibitors • Competitive: a substance that competes with the substrate for the same binding site. Ex: isopropyl and ethyl alcohol

  16. Noncompetitive: substance that binds to an alternative site (allosteric site) on the enzyme, changing its shape, and preventing it from binding to the substrate

  17. Allosteric inhibitors – act as “on/off” switches; bind to allosteric site and reduce enzyme activity • Allosteric activators – bind to allosteric site and increase enzyme activity by keeping enzyme active

  18. Cofactors – minerals that aid enzyme activity • Coenzmye – nonprotein, organic molecule that aids enzyme activity; vitamins

  19. Feedback Inhibition • Final product in a biochemical pathway becomes an allosteric effector on one of the molecules in the pathway and stops the process. • Ex: glucose and insulin

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