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Chapter 19 Electron Transport & Oxidative Phosphorylation PowerPoint Presentation
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Chapter 19 Electron Transport & Oxidative Phosphorylation

Chapter 19 Electron Transport & Oxidative Phosphorylation

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Chapter 19 Electron Transport & Oxidative Phosphorylation

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  1. Chapter 19 Electron Transport & Oxidative Phosphorylation

  2. From Lehninger Principles of Biochemistry

  3. Ubiquinone (coenzyme Q) (from lipids lecture)

  4. 6 carbon C6H12O6 + 6 O2  6 CO2 + 6 H2O 2 x 3 carbon 2 CO2 2 x 2 carbon The carbon is already converted to CO2. What is left is electrons in the form of NADH and FADH2. 2 x 2 CO2

  5. From Garrett & Grisham

  6. {80% proteins} {30-40% lipids & 60-70% proteins} Provide inner membrane with large surface area Intermembrane space • Outer Membrane • Contains porin • Allows free diffusion of molecules • with molecular weight less than • 10,000 Porins are transmembrane channels for small molecules • Inner Membrane • Impermeable to molecules & ions

  7. Matrix • contains all of TCA cycle enzymes {except, succinate dehydrogenase which is located in the inner membrane} • contains circular DNA, ribosomes and enzymes required to synthesize proteins encoded within the mitochondrial genome From Lehninger Principles of Biochemistry

  8. Separation of functional complexes of the respiratory chain Components of the electron transport chain can be purified from the mitochondrial inner membrane From Lehninger Principles of Biochemistry

  9. NAD+/NADH From Lehninger Principles of Biochemistry

  10. Coenzyme Q

  11. FAD/FADH2 & FMN/FMNH2

  12. Heme is the prosthetic group of cytochromes The heme iron atom can undergo a 1 electron transition between ferric and ferrous states:  Fe3+ + e- Fe2+

  13. Electrons transferred via NADPH Electrons transferred via NADPH

  14. Electron Transport Link between glycolysis, TCA cycle, fatty acid oxidation and electron transport chain • e- carried by reduced coenzymes are passed through a chain of proteins and coenzymes to drive the generation of a proton gradient across the inner mitochondrial membrane

  15. 2 other ways to feed electrons into ubiquinone

  16. From Lehninger Principles of Biochemistry

  17. Electron transfer from NADH to O2 involves multi-subunit inner membrane complexes I, III, & IV, plus coenzyme Q and cytochrome c. Within each complex, electrons pass sequentially through a series of electron carriers.

  18. The electron transport chain NADH FADH2 Fe.S FMN Fe.S Q Cyt b Fe.S Cyt c1 Free Energy Relative to O2 (kcal / mol) Cyt c Cyt a Cyt a3 O2 NADH (reductant) + H+ + 1/2 O2 (oxidant) NAD+ + H2O Electrons generally fall in energy through the chain - from complexes I and II to complex IV

  19. Redox reactions are among a cell's most important enzyme-catalyzed reactions. Oxidation and reduction refer to the transfer of one or more electrons from a donor to an acceptor, generally of another chemical species. The donor is oxidized, the acceptor reduced.

  20. Oxidative Phosphorylation The proton gradient runs downhill to drive the synthesis of ATP

  21. Electron Carriers: • FMN (Flavin Mono Nucleotide) is a prosthetic group of some flavoproteins{It is similar in structure to FAD, but lacks the adenine nucleotide} • In solution FMN (like FAD) can accept 2 e- + 2 H+ to yield FMNH2 • When bound at the active site of some enzymes, FMN can accept 1 e-, converting it to the half-reduced semiquinone radical. The semiquinone can accept a second e- to yield FMNH2

  22. Prosthetic groups of cytochromes • Heme  is a prosthetic group of cytochromes • Mitochondria has 3 classes of cytochromes, designated a, b, and c The heme iron atom can undergo a 1 electron transition between ferric and ferrous states:  Fe3+ + e- Fe2+

  23. Structure of mitochondrial cytochrome c From Garrett & Grisham Heme is covalently linked to the protein via S atoms

  24. Iron-sulfur centers (Fe-S) • - Electron transfer proteins may contain multiple iron-sulfur centers. • they transfer only one electron even when they contain two or more iron atoms, because of the close proximity of the iron atoms.  a 4-Fe center might cycle between the redox states: Fe3+3Fe2+1 (oxidized) + 1 e-Fe3+2 Fe2+2( reduced)

  25. Iron-sulfur centers From Lehninger Principles of Biochemistry

  26. Ferredoxin of the cyanobacterium Anabaena 7120 2Fe-2S center Fe S From Lehninger Principles of Biochemistry

  27. Protein bound copper, a one-electron transfer site, which converts between Cu+ and Cu2+

  28. Ubiquinone (Q or coenzyme Q) From Lehninger Principles of Biochemistry

  29. A lipid soluble coenzyme (UQ) shuttle between protein complexes Mobile electron carrier

  30. Complex I