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Citrate Cycle (CC)

Citrate Cycle (CC). Vladimíra Kvasnicová. Citrate cycle is also called. citric acid cycle tricarboxylic acid cycle Krebs cycle electron transport chain.

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Citrate Cycle (CC)

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  1. Citrate Cycle(CC) Vladimíra Kvasnicová

  2. Citrate cycle is also called • citric acid cycle • tricarboxylic acid cycle • Krebs cycle • electron transport chain

  3. 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

  4. simplification: The figure is found at http://www.sp.uconn.edu/~bi107vc/images/mol/krebs_cycle.gif (December 2006)

  5. citric acid (2-hydroxypropane-1,2,3-tricarboxylicacid)

  6. Hans Adolf Krebs The Nobel Prize in Physiology or Medicine in 1953 for his discovery of the citric acid cycle.

  7. 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

  8. Citrate cycle • is a catabolic pathway • participates in anabolic reactions • belongs among oxidative processes • produces carbon dioxide

  9. The figure is found at http://www.holon.se/folke/kurs/Distans/Ekofys/Recirk/Eng/regcyc5.jpg (December 2006)

  10. Amphibolic nature of thecitrate cycle The figure is found athttp://www.tcd.ie/Biochemistry/IUBMB-Nicholson/gif/13.html

  11. Enzymes of the citrate cycle • are found in all cells • are located in a mitochondrion • catalyze freely reverzible reactions • produce coenzymes which are regenerated in a respiratory chain

  12. strongly exergonic reactions The figure is found at http://www.metabolic-database.com/html/body_glutaminolysis__zeichnung3.html (December 2006)

  13. The substances enter the CC • acetyl~CoA • NAD+ and FAD • carbon skeleton of amino acids • GDP

  14. The figure is found at http://www.elmhurst.edu/~chm/vchembook/images/590metabolism.gif (December 2006)

  15. Choose products of the cycle • pyruvate • acetyl-CoA • NADH • FADH2

  16. Products of the citrate cycle The figure is found at http://www.hupe.hu/szerv/tanszekek/kio/im/oktat/SEJTBIO/citratkor/citr_summa_e.html (December 2006)

  17. Energy released from oxidation of acetyl group in the CC is conserved in • GTP • ATP • NADH • FADH2

  18. The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)

  19. NAD+ is reduced to NADH+H+ in the reactions of the CC • isocitrate → -ketoglutarate • -ketoglutarate → succinyl~CoA • succinate → fumarate • malate → oxaloacetate

  20. „F“ →Fumarateand FADH2 The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)

  21. Carbon dioxide (CO2) is produced in the reactions of the CC • oxaloacetate + acetyl~CoA → citrate • citrate → isocitrate • isocitrate → -ketoglutarate • -ketoglutarate → succinyl~CoA

  22. The figure is found at http://lecturer.ukdw.ac.id/dhira/Metabolism/Respiration.html (December 2006)

  23. Choose reactions that lead tonet synthesis of CC intermediates(= anaplerotic reactions) • pyruvate → acetyl~CoA (PDH) • pyruvate → oxaloacetate (pyruvate carboxylase) • aspartate → oxaloacetate (AST) • glutamate → -ketoglutarate (ALT)

  24. The figure is found at http://web.indstate.edu/thcme/mwking/tca-cycle.html (prosinec 2006)

  25. The most important anaplerotic reaction: pyruvate carboxylase The figure is found at http://www.bmb.leeds.ac.uk/illingworth/metabol/2120lec3.htm#krebs (December 2006)

  26. The substances can be synthesized from intermediates of the CC • amino acids • heme • glucose • fatty acids

  27. Citrate cycleas a source of substrates used in a synthesis of other molecules The figure is found athttp://www.tcd.ie/Biochemistry/IUBMB-Nicholson/gif/13.html

  28. The enzymes regulate velocity of the CC • citrate synthase • isocitrate dehydrogenase • -ketoglutarate dehydrogenase • hexokinase

  29. The citrate cycle is inhibited by •  ATP/ADP •  NADH,  NAD+ •  NADH/NAD+ •  AMP

  30. Regulation of the citrate cycle = by availability of substrates and consumption of produts

  31. Citrate • is formed from oxaloacetate and acetic acid • is transported to the cytoplasm if accumulates • acts as an inhibitor of glycolysis • activates synthesis of fatty acids

  32. ATP The figure is found at http://www.metabolic-database.com/html/body_glutaminolysis__zeichnung3.html (December 2006)

  33. see next presentation 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

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