Lecture 3Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Lecture 3•August 5, 2005•Lehninger (4th Edition), Chapter 13METABOLIC PATHWAYSTypes of Organic Reactions1) Group transferGlucose + ATP Glu-6-P + ADPH2O + ATP Pi + ADP2) Oxidation-reduction reactionsEthanol + NAD+ acetaldehyde + NADH + H+3) Eliminations, isomerizations, rearrangementsaldose ketose4) reactions involving making or breaking of C-C bondsFru-1,6, bisphosphate dihydroxyacetone-phosphate + glyceraldehyde-3phosphateBiochemical reactions are subject to the laws of thermodynamicsA + B C + DG = 0 at equilibriumGas constant R = 8.313 J/mol.K = 1.987 cal/mol.K1 cal = 4.184 Jat 25oC RT = 2.497 kJ/mol = 0.592 kcal/molMany reactions in biological systems are by themselves not energetically favored (G > 0)they have to be “pushed”1. By changing concentrations of reactants2. By coupling them to energy releasing reactions3. enzymatic mechanisms are designed to accomplish thisHIGH ENERGY PHOSPHATE COMPOUNDSATP_____________a mixed anhydrideLNC 14-8Oxidation - Reduction Reactionsa second major source of chemical free energy for biological work- 4- 1+ 1+ 2+ 4LNC 14.14[lactate] [NAD+]G = Go’ + RT ln --------------------------- [pyruvate] [NADH] [lactate] [NAD+]E = Eo’ - RT/n F ln --------------------------- [pyruvate] [NADH]G = - n F Etransfer of hydride ion(two electrons)in one stepLNC 14-15aLNC 14-15bFADFMNLNC 14-16two stepsone electron and one protontransferred in each stepMETABOLIC PATHWAYS•End of lecture 3•August 5,
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