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SURVEY OF BIOCHEMISTRY Electron Transport and Oxidative Phosphorylation

SURVEY OF BIOCHEMISTRY Electron Transport and Oxidative Phosphorylation. Redox Centers. Zoom in on the cristae:. The Mitochondrion. ~2000 per cell. How does electron transfer work?. NADH binds to Complex I on the matrix side of the membrane. Electron Transfer with NADH.

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SURVEY OF BIOCHEMISTRY Electron Transport and Oxidative Phosphorylation

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  1. SURVEY OF BIOCHEMISTRYElectron Transport and Oxidative Phosphorylation

  2. Redox Centers

  3. Zoom in on the cristae: The Mitochondrion ~2000 per cell

  4. How does electron transfer work? NADH binds to Complex I on the matrix sideof the membrane

  5. Electron Transfer with NADH FMN resembles FAD without the adenine dinucleotide group NADH transfers its e-to redox centers in Complex I 2e- go to FMN…

  6. Electron Transfer with FMNH2 FMNH2 can then pass each e- to series of Fe-S clusters in a stepwise manner: NADH transfers 2e-to FMN - a redox center in Complex I

  7. Fe-S Clusters in Complex I Complex I contains Fe-S clusters as cofactors

  8. Coenzyme Q (Ubiquinone) Electrons pass from Fe-Sclusters to a “mobile”electron carrier cofactor called Coenzyme Q

  9. Electron Transfer with CoQ Coenzyme Q initially binds to Complex I to pick up 2 e- from the Fe-S clusters in Complex I

  10. Complex II Succinate-Coenzyme Q Oxidoreductase Complex II is notshownElectrons pass fromFADH2 to CoQvia Complex II 4H+ ions get pumped out of the matrix by Complex I and CoQbut not Complex II FADH2

  11. Electron Transfer with CoQ Coenzyme Q binds to Complex III on the Intermembrane space side One e- goes to Cytochrome c One e- goes into the Q cycle

  12. Electron Transfer with Cyt c Once CoQ loses its 2e-, it can dissociate from the upper region of Complex III and rebind near the matrix sideand pick up the e- it just donated! Meanwhile, Cytochrome c carries its e- to Complex IV

  13. Electron Transfer with Cyt c Another CoQ carrying 2e- can bind to Complex III, passing one of its e- to Cytochrome c and one into the Q cycle and ultimately to the original CoQ molecule.

  14. Proton Pumping from Matrix 4 H+ ions get pumped from matrixinto the intermembrane spaceas 2 electrons are passed through Complex I (mechanism unknown) NADH FMN Fe-S CoQ

  15. Complex III and Complex IV Cytochrome bc1 Cytochrome c oxidase O2 + 4 H+ 2H2O How does ATP get made?

  16. Chemiosmotic Theory Idea that the free energy needed to transport e- is conserved by the formation of a transmembrane proton gradient. Proton gradient drives ATP synthesis.

  17. Complex V: ATP Synthase F1F0 ATPase F0 - water insolublew/ 8 types of subunits F1 - water solubleperipheral membraneprotein w/ 5 types of subunits

  18. Binding Mechanism in ATP Synthase • ATP binds into the T protomer first • ADP and Pi bind to the L protomer • Supply of energy induces a conformational change • ATP goes to the O protomer and is released • ATP is synthesized at the T protomer O = open L = loose T = tight

  19. Overview of Electron Transport Notice theseinhibitors of electron transport!

  20. Coordinated Control of Glycolysis and the TCA Cycle

  21. Anaerobic Metabolism of Glucose: C6H12O6 + 2 ADP + 2 Pi 2 Lactate + 2 H+ + 2 H2O + 2 ATP Aerobic Metabolism of Glucose: C6H12O6 + 32 ADP + 32 Pi + 6O2 6 CO2 + 38H2O + 32 ATP Pros and Cons of Aerobic Metabolism PRO: Aerobic metabolism is up to 16x more productivethan anerobic metabolism!

  22. Pros and Cons of Aerobic Metabolism O2 + e- O2-• Superoxideradical Other harmful possibilities: H2O2 + Fe2+ •OH + OH- + Fe3+ O2-• + H2O2 O2 + H2O + •OH CON: Aerobic metabolism, with its high efficiency, tendsto produce free radicals of oxygen!

  23. 2O2-• + 2H+ O2 + H2O2 Otherpotentialantioxidants Superoxide Dismutase (SOD) • An inherent antioxidant enzyme SOD 2H2O2 Catalase 2 H2O+ O2

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