Electron Transport Chain (Respiratory Chain)

1. Electron Transport Chain(Respiratory Chain) Vladimíra Kvasnicová

2. Respiratory chain (RCH) • is found in all cells • is located in a mitochondrion • includes enzymes integrated in the inner mitochondrial membrane • produces reducing equivalents (NADH+H+, FADH2)

3. The figure is found at http://plaza.ufl.edu/tmullins/BCH3023/cell%20respiration.html (December 2006)

4. Respiratory chain (RCH) • belongs among oxidative pathways • can proceed under both aerobic and anaerobic conditions • is a reversible pathway • needs oxygen (O2) for its function

5.  reducing properties Redox potential „E“ Gibbs energy„G“  oxidizing properties The figure is found at http://www.grossmont.net/cmilgrim/Bio220/Outline/ECB2Figures&Tables_Ed2-Ed1/Chapter14_13/REDOX_POTENTIALS_ElectronTransportChain_Fig14-21.htm (December 2006)

6. The figure is found at http://academic.brooklyn.cuny.edu/biology/bio4fv/page/mito_ox.htm (December 2006)

7. Enzymes of the RCH • belong among oxidoreductases • can transfer either H or electrons • are called Complex I, II, III and IV • transfer protons and electrons in the same direction

8. proton= H+ electron= e- Cytochrome c is drawn wrongly! It is found in the intermembrane space, bound to the inner mitochondrial membrane The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

9. The function of the RCH • is to regenerate NAD+ from NADH • is to regenerate NADP+ from NADPH • is to regenerate FAD from FADH2 • is to finish oxidation of energy substrates and conserve their energy in a form of ATP

10. In reactions of the RCH • oxygen is reduced to H2O • protons (H+) are transfered into an intermembrane space • ATP is produced by the Complex I • all reduced coenzymes (NADH+H+ and FADH2) are reoxidized by the same mechanism

11. The figure is found at http://www.cellml.org/examples/images/metabolic_models/the_electron_transport_chain.gif (December 2006)

12. Choose correct statement • Complex I transfers H+ into an intermembrane space • Complex II transfers H+ into an intermembrane space • Coenzyme Q accepts e- from both Complex I and Complex II • Complex IV transfers electrons to oxygen

13. proton= H+ electron= e- Cytochrome c is drawn wrongly! It is found in the intermembrane space, bound to the inner mitochondrial membrane The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

14. Citrate cycle (CC) and the RCH are interconnected • by CO2 (produced by CC, used by RCH) • by NADH (produced by CC, used by RCH) • an enzyme succinate dehydrogenase • ATP (produced by RCH, used by CC)

15. Citrate cycle succinate DH The figure is found at http://www.cellml.org/examples/images/metabolic_models/the_electron_transport_chain.gif (December 2006)

16. Adenosine triphosphate (ATP) • can be produced only in a cooperation with RCH • can be synthesized only under aerobic conditions • is formed from ADP by addition of one phosphate • is transported from a mitochondrion into a cytoplasm by exchange with ADP

17. ATP-ADP translocase The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

18. When the term is used it always means „ATP synthesis“ • phosphorylation • oxidative phosphorylation • aerobic phosphorylation • substrate level phosphorylation

19. Oxidative phosphorylation • needs proton gradient on the inner mitochondrial membrane • is catalyzed by ATP synthase • can be interrupted by uncoupling proteins (UCP) • means ATP synthesis in any oxidative metabolic pathway

20. The figure is adopted from the book: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley‑Liss, Inc., New York, 1997. ISBN 0‑471‑15451‑2

21. inner mitochondrial membrane ATP synthase The figure is found at http://plaza.ufl.edu/tmullins/BCH3023/cell%20respiration.html (December 2006)

22. Uncoupling proteins(UCP) = separate RCH from ATP synthesis(the synthesis is interrupted) energy from H+ gradient is released as a heat The figure is found at http://departments.oxy.edu/biology/Franck/Bio222/Lectures/March23_lecture_shuttles.htm (December 2006)

23. ATP (or GTP)can be formed by the reactions • glucose-6-P + ADP → glucose + ATP • succinyl~CoA + GDP → succinate + GTP • GTP + ADP → GDP + ATP • ADP + ADP → ATP + AMP

24. Oxidation of NADH+H+ in the RCH produces more ATP than oxidation of FADH2 because • higher proton gradien is made by oxidation of NADH+H+ • NADH+H+ transfers H to different Complex of the RCH than FADH2 • more protons are transported to the intermembrane space if NADH+H+ is oxidized • more e- are transfered from NADH+H+ to O2

25. FADH2 The figure is found at http://web.indstate.edu/thcme/mwking/oxidative-phosphorylation.html (December 2006)

26. Choose correct statement(s) about regulation of RCH and ATP synthesis •  O2 decreases the pathways • uncoupling proteins increase ATP synthesis •  ADP increses ATP synthesis •  NADH+H+/NAD+ increases the pathways