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intro

Redox reactions. 1: hydrogenase/dehydrogenase. intro. 2) oxygenase/reductase. intro. Remember from Gen Chem?. Cu +2 (aq) + Zn (s)  Cu (s) + Zn +2 (aq). 16.1. reduced: more bonds to H. oxidized: more bonds to O (or N, S, Cl, etc.). 16.1. Learn to quickly spot redox reactions!.

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intro

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  1. Redox reactions 1: hydrogenase/dehydrogenase intro

  2. 2) oxygenase/reductase intro

  3. Remember from Gen Chem? Cu+2(aq) + Zn(s) Cu(s) + Zn+2(aq) 16.1

  4. reduced: more bonds to H oxidized: more bonds to O (or N, S, Cl, etc.) 16.1

  5. Learn to quickly spot redox reactions! 16.1

  6. Redox and metabolism – the big picture Cu+2(aq) + Zn(s) Cu(s) + Zn+2(aq) Cu has higher reduction potential than Zn oxidation of fuel molecules: transfer electrons from organic molecule to O2 16.2

  7. ‘uphill’ redox reactions: recharging the battery Zn+2(aq) + Cu(s) + energy  Zn(s) + Cu+2(aq) 6CO2 + 6H2O + energy  C6H12O6 + 6O2 16.2

  8. more reduced state – more energy of oxidation 16.2

  9. fat has more energy per carbon than sugar (carbons are more reduced) 16.2

  10. biosynthesis is a reductive process: 16.2

  11. Methanogenesis: CO2 is electron acceptor! CO2 + 4H2 CH4 + 2H2O + energy 16.3

  12. Hydrogenation (reduction) of aldehyds, ketones, imines: 16.4

  13. the reverse: dehydrogenation (oxidation) 16.4

  14. hydrogenation (reduction) of acid derivatives: the reverse: dehydrogenation 16.4

  15. But where does :H- come from? Where does it go?

  16. NAD+ / NADH: the main biological redox pair 16.4A

  17. 16.4A

  18. NAD(P)H acts as hydride donor NAD(P)H IS NOT AN ACID!!!!!!! (everyone repeat five times!) 16.4B

  19. NAD(P)+ acts as a hydride acceptor 16.4B

  20. abbreviations: 16.4B

  21. enzymatic hydrogenation is very stereospecific: 16.4C

  22. 16.4C

  23. NAD(P)+ accepts hydride stereospecifically 16.4C

  24. A few actual examples 16.4D

  25. 16.4D

  26. 16.4D

  27. a double hydrogenation: thioester to aldehyde to alcohol 16.4D

  28. carboxylates need to be activated before hydrogenation 16.4D

  29. 16.4D

  30. Hydrogenation (reduction) of alkene: conjugate addition of hydride 16.5A

  31. dehydrogenation (oxidation) of alkane: (fatty acid degradation) requires flavin as oxidizing agent 16.5A

  32. the second biological redox molecule: flavin (without the phosphate: riboflavin) 16.5B

  33. 16.5B

  34. fatty acid degradation: dehydrogenation (oxidation) of alkane carbons 16.5C

  35. it’s an E1cb elimination! 16.5C

  36. flavin also participates in alkene hydrogenation 16.5D

  37. 16.5D

  38. Less common hydrogenase examples 16.5D

  39. 16.6

  40. 16.6

  41. Nucleophilic aromatic substitution/dehydrogenation 16.6

  42. FAD/NAD+ as electron shuttles in catabolism they take electrons (hydride) from organic molecules that we eat 16.7A

  43. . . .and eventually these electrons are shuttled to oxygen 16.7A

  44. NADPH for anabolism (biosynthesis) is generated from pentose phosphate pathway 16.7B

  45. FADH2 can also be reducing agent, but it gets hydrides from NADPH 16.7B

  46. 16.7B

  47. Hydrogenase/dehydrogenase reactions are easy to follow by UV NADH absorbs at 340nm NAD+ does not 16.8

  48. Hydrogen and renewable energy (wind turbine?) 2H20 + energy  2H2 + O2 some hydrogenases make H2 (biohydrogen) NADP-H + H+ H-H + NADP+ other ways to store energy from H2: 1) N2 + 6H2 2NH3 2) CO2 + 3H2 CH3OH + H2O 16.9

  49. Oxygenases and reductases – adding/eliminating oxygen (cortisol pathway) 16.10

  50. some oxygenases use flavin 16.10

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