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Lecture 3

Lecture 3. August 5, 2005 Lehninger (4 th Edition), Chapter 13 . METABOLIC PATHWAYS. Types of Organic Reactions 1) Group transfer Glucose + ATP Glu-6-P + ADP H 2 O + ATP P i + ADP

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Lecture 3

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  1. Lecture 3 • August 5, 2005 • Lehninger (4th Edition), Chapter 13

  2. METABOLIC PATHWAYS

  3. Types of Organic Reactions • 1) Group transfer • Glucose + ATP Glu-6-P + ADP • H2O + ATP Pi + ADP • 2) Oxidation-reduction reactions • Ethanol + NAD+ acetaldehyde + NADH + H+ • 3) Eliminations, isomerizations, rearrangements • aldose ketose • 4) reactions involving making or breaking of C-C bonds • Fru-1,6, bisphosphate dihydroxyacetone-phosphate • + glyceraldehyde-3phosphate

  4. Biochemical reactions are subject to the laws of thermodynamics

  5. A + B C + D DG = 0 at equilibrium

  6. Gas constant • R = 8.313 J/mol.K • = 1.987 cal/mol.K • 1 cal = 4.184 J • at 25oC RT = 2.497 kJ/mol • = 0.592 kcal/mol

  7. Many reactions in biological systems are by themselves not energetically favored (DG > 0) they have to be “pushed” 1. By changing concentrations of reactants 2. By coupling them to energy releasing reactions 3. enzymatic mechanisms are designed to accomplish this

  8. HIGH ENERGY PHOSPHATE COMPOUNDS ATP

  9. _ _ _ _ _ _ _ _

  10. _ _ _ _ _

  11. a mixed anhydride

  12. LNC 14-8

  13. Oxidation - Reduction Reactions a second major source of chemical free energy for biological work

  14. - 4 - 1

  15. + 1 + 2 + 4

  16. LNC 14.14

  17. [lactate] [NAD+] DG = DGo’ + RT ln --------------------------- [pyruvate] [NADH] [lactate] [NAD+] DE = DEo’ - RT/n F ln --------------------------- [pyruvate] [NADH] DG = - n FDE

  18. transfer of hydride ion (two electrons) in one step LNC 14-15a

  19. LNC 14-15b

  20. FMN FAD two steps one electron and one proton transferred in each step LNC 14-16

  21. METABOLIC PATHWAYS

  22. End of lecture 3 August 5, 2005

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