1 / 25

Lecture 21

Lecture 21. Mitochondrial Electron Transfer. Biological Electron Flow Does Work. Mitochondrial Electron Carriers. NADH and FADH 2 (Flavoproteins) Dehydrogenases Iron-sulfur proteins Cytochromes Cu Ubiquinone (Coenzyme Q CoQ). Highly organized complexes on inner mitochondrial membrane.

moses
Télécharger la présentation

Lecture 21

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 21 Mitochondrial Electron Transfer

  2. Biological Electron Flow Does Work

  3. Mitochondrial Electron Carriers • NADH and FADH2 (Flavoproteins) • Dehydrogenases • Iron-sulfur proteins • Cytochromes • Cu • Ubiquinone (Coenzyme QCoQ) Highly organized complexes on inner mitochondrial membrane

  4. Nicotinamide-Adenine Dinucleotide

  5. Reduction of Flavin Nucleotides

  6. Iron-Sulfur Proteins (Fe-S) Fe+3 + e– Fe2+ Fe-S clusters: Fe between +3 and +2 oxidation states Redox range [2Fe-2S]2+/1+:-240 to -460 mV [4Fe-4S]3+/2+:50 to 450mV

  7. Heme in cytochrome

  8. Electron-Transfer Complexes: H+ Pumps As electrons flow to O2, H+ flows out

  9. Electron transfer complexes • I: NADH Q oxidoreductase • II: Succinate dehydrogenase • III: Ubiquinone cytochrome c • oxidoreductase • IV: Cytochrome oxidase In between some complexes:electron carriers that diffuse out of complex

  10. Carrier Order by Inhibition • Carriers ahead of block are reduced • Carriers behind block are oxidized

  11. Complex I:NADH Ubiquinone oxidoreductase NADH + H+ +Q NAD+ + QH2

  12. Electron-Transfer Complexes: H+ Pumps As electrons flow to O2, H+ flows out

  13. Ubiquinone  UQ  CoQ Two electron carrier

  14. Q cycle:Complex III

  15. Complex IV Redox centers: Carry only 1e- at a time. Reactive intermediates are generated.

  16. Order of Carriers: Ascending Eo

  17. Respiration in Mitochondria • 3 reactions • Substrate is oxidized • O2 consumed (H2O) • ADP + Pi  ATP

  18. Uncoupling Agents and Conditions • Allow electron flow without ATP synthesis • Example: 2,4-dinitrophenol (DNP) • Others: CCCP, ionophores, membrane disruption

  19. + 1 + NADH + H + / O H O + NAD 2 2 2 o ∆G ' = –220 kJ/mol ADP + P ATP i o ∆G ' = +30.5 kJ/mol Efficiency of Oxidative Phosphorylation

  20. Observed P/O Ratios

  21. Phosphorylation “Substrate-level” vs. “Respiration-linked”

  22. Chemiosmotic Energetics In mitochondria ∆GH+=15-25 kJ/mol H+

  23. Predictions of Chemiosmotics 1. Electron transfer causes H+ flux 2. Destruction of H+ gradient blocks ATP synthesis 3. Artificially-induced H+ gradient drives ATP synthesis without electron transfer 4.Blocking ATP synthesis will eventually inhibit electron transfer

  24. H+ Flux Across Mitochondrial Membrane

  25. Uncouplers: Permeant H+ Carriers Destroys H+ gradient

More Related