369Lecture15_F11 - + 1 CH369 Fall 2011 Lecture 15: Ch 15...

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+ Lecture 15: Ch 15 Oxidative Phosphorylation CH369 Fall 2011 1
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+ Defining Ox-Phos n Oxidative n Process that involves electron extraction n Electrons passed through ETS and ultimately to terminal electron acceptor n Generates energy and pumps protons n Energy stored as proton gradient n Like building charge in battery n Phosphorylation n Synthesis of ATP from ADP + P i n Converts energy stored as proton gradient into energy stored in chemical bond 2
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+ Recovering Energy n Oxidative phosphorylation n Converting electron energy into ATP n Indirectly coupled n Very efficient recovery of energy n Last phase of extracting energy out of biomolecules n Follow the electrons! 3
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+ Redox Thermodynamics n Oxidation is loss (OIL); reduction is gain (RIG) n If you extract electrons from one donor, you must deposit them on acceptor n FADH 2 + Q ßà FAD + QH 2 n Reaction can be expressed as half-reactions n Only look at one substance at a time n Q + 2 H + + 2 e - ßà QH 2 n Standard reduction potential ( E ° ` ) n Tendency of the oxidized form to be reduced (accept electrons) n Larger the + value – the greater the tendency n Actual reduction potential depends on concentrations of species 4 reduced oxidized reduced oxidized
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+ Nernst Equation n Actual reduction potential n R is gas constant (8.3145 J/K/mol); T is temp (Kelvin); n = number of electrons transferred; F is Faraday constant (96.485 J/V/mol) n At 25°C (298K): 5 E = E ! ° + RT nF ln A reduced [ ] A oxidized [ ] E = E ! ° + 0.026 V n ln A reduced [ ] A oxidized [ ]
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+ Free Energy Changes n Reduction potential predict flow of electrons n Flow from substance with lower to higher potential n Lower or negative reduction potential means it is more likely to donate than receive electrons n Ex: e - flow from NADH (-0.315) to Q (+0.045) n Net: n Highest reduction potential: O 2 6 ! E " ° = E " ° ( e # acceptor ) # E " ° ( e # donor ) = 0.045 V - (- 0.315 V) = +0.360
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+ Free Energy Changes 7 n The larger the value of ϶ E, the greater the tendency of the electrons to flow in that direction and the greater the change in free energy n Large negative for ϶ G requires + ϶ E n Electrons flow down the transport chain according to reduction potential ! G " ° = # nF ! E " ° or ! G = # nF ! E
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+ Respiration n Respiration involves the use of the electron transport system (ETS) n Electrons ultimately passed to O
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369Lecture15_F11 - + 1 CH369 Fall 2011 Lecture 15: Ch 15...

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