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Chemistry of Life: enzymes and reaction rates

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2 4 10

  1. 1. Chapter Two The Chemistry of Life<br />Section 2-4<br />Chemical Reactions and Enzymes<br />
  2. 2. Chemical Reactions<br />Chemical reaction – a process that changes (or transforms) one set of chemicals into another.<br />examples<br />A + B î C + D<br />A + B î C<br />A î E + F<br /><ul><li>Chemical Reactions
  3. 3. Energy in Reactions
  4. 4. Enzymes
  5. 5. Enzyme Action</li></li></ul><li>Chemical Reactions<br />Parts of a reaction<br />Reactants are the elements or compounds that enter into (begin) a chemical reaction.<br />Products are the elements or compounds that are produced by (result from) a chemical reaction.<br />Reactants Products<br /><ul><li>Chemical Reactions
  6. 6. Energy in Reactions
  7. 7. Enzymes
  8. 8. Enzyme Action</li></li></ul><li>Chemical Reactions<br />Chemical reactionsalways involve changes in the chemical bonds that join atoms in compounds.<br /><ul><li>Chemical Reactions
  9. 9. Energy in Reactions
  10. 10. Enzymes
  11. 11. Enzyme Action</li></li></ul><li>Energy in Reactions<br />Depending on the number and types of chemical bonds broken and formed, energy may be either releasedorabsorbed by chemical reactions.<br /><ul><li>Chemical Reactions
  12. 12. Energy in Reactions
  13. 13. Enzymes
  14. 14. Enzyme Action</li></li></ul><li>Energy in Reactions<br />Recall (from 2 minutes ago) that<br />Reactants are the elements or compounds that enter into (begin) a chemical reaction.<br />Products are the elements or compounds that are produced by (result from) a chemical reaction.<br /><ul><li>Chemical Reactions
  15. 15. Energy in Reactions
  16. 16. Enzymes
  17. 17. Enzyme Action</li></li></ul><li>Energy in Reactions<br />If the reactants (the starting conditions) have more energy than the products (the ending conditions), then energy is released (also known as an exothermic reaction).<br /><ul><li>Chemical Reactions
  18. 18. Energy in Reactions
  19. 19. Enzymes
  20. 20. Enzyme Action</li></li></ul><li>Energy in Reactions<br />If the reactants (the starting conditions) have less energy than the products (the ending conditions), then energy is absorbed(also known as an endothermic reaction).<br /><ul><li>Chemical Reactions
  21. 21. Energy in Reactions
  22. 22. Enzymes
  23. 23. Enzyme Action</li></li></ul><li>Endo- and Exothermic Reactions<br />Endothermic Reaction<br />Exothermic Reaction<br />Energy-Releasing Reaction<br />Energy-Absorbing Reaction<br />Activation <br />energy<br />Products<br />Activation energy<br />Reactants<br />Reactants<br />Products<br /><ul><li>Chemical Reactions
  24. 24. Energy in Reactions
  25. 25. Enzymes
  26. 26. Enzyme Action</li></li></ul><li>Energy in Reactions<br />Activation energy is the energy needed to get a chemical reaction started. <br />Example<br />Paper (cellulose) burns in the presence of oxygen and releases heat and light.<br />Why then aren’t your books all on fire?<br />You need a spark to get the reaction started.<br /><ul><li>Chemical Reactions
  27. 27. Energy in Reactions
  28. 28. Enzymes
  29. 29. Enzyme Action</li></li></ul><li>Energy in Reactions - facts<br />Chemical reactions that release energy often occur spontaneously.<br />Chemical reactions that absorb energy will not occur without a source of energy.<br /><ul><li>Chemical Reactions
  30. 30. Energy in Reactions
  31. 31. Enzymes
  32. 32. Enzyme Action</li></li></ul><li>Energy in Reactions<br />In reversible reactions, one direction will produce energy, A + B î C + D + energy<br />and the other direction will require energy, C + D + energyî A + B<br /><ul><li>Chemical Reactions
  33. 33. Energy in Reactions
  34. 34. Enzymes
  35. 35. Enzyme Action</li></li></ul><li>
  36. 36. Enzymes<br />A catalyst is a substance that speeds up the rate of a chemical reaction.<br />A catalyst does this by lowering a reaction’s activation energy.<br /><ul><li>Chemical Reactions
  37. 37. Energy in Reactions
  38. 38. Enzymes
  39. 39. Enzyme Action</li></li></ul><li>Enzymes<br />Enzymes are proteins that act as biological catalysts. <br />Enzymes speed up chemical reactions that take place in cells.<br />Like other catalysts, enzymes do this by lowering the activation energy of a reaction.<br /><ul><li>Chemical Reactions
  40. 40. Energy in Reactions
  41. 41. Enzymes
  42. 42. Enzyme Action</li></li></ul><li>Energy diagram of a chemical reaction<br />Reaction pathway<br />without enzyme<br />Activation energy<br />without enzyme<br />Activation<br />energy<br />with enzyme<br />Reactants<br />Reaction pathway<br />with enzyme<br />Products<br />In terms of energy, what an enzyme (or any catalyst) does to a reaction is to lower the activation energy.<br />
  43. 43. Enzymes<br />Without enzymes, the thousands of chemical reactions necessary to sustain life would simply be <br /> t o o s l o w.<br /><ul><li>Chemical Reactions
  44. 44. Energy in Reactions
  45. 45. Enzymes
  46. 46. Enzyme Action</li></li></ul><li>Enzyme Action<br />Enzymes work by creating an ideal environment for the reaction to take place.<br />Proximity<br />Orientation<br />This reduces the energy needed for the reaction to take place.<br /><ul><li>Chemical Reactions
  47. 47. Energy in Reactions
  48. 48. Enzymes
  49. 49. Enzymes Action</li></li></ul><li>Enzyme Action<br />The reactants of enzyme-catalyzed reactions are known as substrates. <br />Substrates bind to a specific location on the enzyme known as the active site.<br /><ul><li>Chemical Reactions
  50. 50. Energy in Reactions
  51. 51. Enzymes
  52. 52. Enzymes Action</li></li></ul><li>Enzyme Action<br />This association is called the enzyme-substrate complex.<br />The fit between substrate and active site is so precise that it is frequently compared to a “lock and key”.<br /><ul><li>Chemical Reactions
  53. 53. Energy in Reactions
  54. 54. Enzymes
  55. 55. Enzymes Action</li></li></ul><li>Enzyme Action<br />It is the shape of these large enzyme molecules that allows them to function.<br />Changes in pH or temperature can cause changes in an enzyme’s shape that can reduce (or destroy) its effectiveness as a catalyst (read “Analyzing Data” on pg. 51 in your text). (Denaturing the enzyme)<br /><ul><li>Chemical Reactions
  56. 56. Energy in Reactions
  57. 57. Enzymes
  58. 58. Enzymes Action</li></li></ul><li>Enzyme animation<br />
  59. 59. The end of Chapter Two The Chemistry of Life<br />
  60. 60. http://www.stolaf.edu/people/giannini/flashanimat/enzymes/biochem.path.swf<br />http://www.dannynicholson.co.uk/enzymetale.swf<br />
  61. 61. http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf<br />
  62. 62.
  63. 63. http://www.northland.cc.mn.us/biology/Biology1111/animations/enzyme.swf<br />http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf<br />http://www.tvdsb.on.ca/westmin/science/sbi3a1/digest/enzymes.htm<br />http://www.hillstrath.on.ca/moffatt/bio3a/digestive/enzanim.htm<br />http://www.stolaf.edu/people/giannini/flashanimat/enzymes/enzyme.swf<br />http://www.biotopics.co.uk/other/anenz.html<br />http://www.dannynicholson.co.uk/enzymetale.swf<br />http://www.stolaf.edu/people/giannini/flashanimat/enzymes/biochem.path.swf<br />http://www.sigmaaldrich.com/Area_of_Interest/Life_Science/Metabolomics/Key_Resources/Metabolic_Pathways/Glycolytic_Pathway.html<br />http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120070/bio09.swf::A%20Biochemical%20Pathway<br />
  64. 64. Chemical Reactions and Enzymes (2-4)<br />Chemical Reactions (today)<br />Energy in Reactions (today)<br />Enzymes (10/9)<br />Enzyme Action (10/9)<br />

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