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Lecture 27

Lecture 27. Electron Transfer in Biology. Mechanical Work Driven by Electrons. Biological Electron Flow Does Work. Oxidation and Reduction of Carbon. LEO says GER L ose e lectrons: o xidized. G ain e lectrons: r educed Feº + O 2  Fe 2 O 3 (rust) CH 3 CH 2 CH 3  3CO 2 + 4H 2 O.

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Lecture 27

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  1. Lecture 27 Electron Transfer in Biology

  2. Mechanical Work Driven by Electrons

  3. Biological Electron Flow Does Work

  4. Oxidation and Reduction of Carbon LEO says GER • Lose electrons: oxidized. Gain electrons: reduced Feº + O2 Fe2O3 (rust) CH3CH2CH3  3CO2 + 4H2O

  5. Electron-Sharing by Carbon

  6. Electrochemistry: Half-Reactions

  7. Standard Reduction Potentials • When 2 “half-cells” are connected, which direction will electrons flow?

  8. Standard Reduction Potentials (Eo)

  9. Nernst Equation

  10. Compare These Equations

  11. Relationship of ∆Eº and ∆Gº

  12. Biological Electron Carriers • “Pyridine” nucleotides • NAD+ • NADP+ • Flavine nucleotides • FMN • FAD • Cytochromes • Iron-sulfur proteins • Quinones • Lipoamide

  13. Nicotinamide-Adenine Dinucleotide

  14. Reduction of NAD+ by Two Electrons

  15. Dehydrogenases and NAD+

  16. Some Typical Dehydrogenases All use NAD+ as electron acceptor

  17. Stereospecificity of H Transfer

  18. Stereospecific NAD+ Reduction

  19. Flavin Nucleotides FMN, FAD

  20. Reduction of Flavin Nucleotides

  21. Some Typical Flavoproteins Flavoproteins bind flavin nucleotides very tightly *Sometimes covalently

  22. Some Practical Applications 1. How to measure rate of reaction? 2. Which direction will it go? 3. How energetic is it?

  23. Spectral Change by Reduction of NAD+ So appearance of NADH  peak of A340

  24. Measuring Rate of NADH Production From A340 and molar extinction coefficient of NADH, you can calculate moles of NADH produced per time

  25. Direction of Redox Reaction

  26. How Energetic is this Reaction?

  27. How can we Oxidize Ethanol? 1. Remove the product Ethanolacetaldehydeacetate1 CO2 2. Have appropriate ratio of

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