Ciclo de krebs

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Ciclo de krebs

  1. 1. Ciclo de KrebsFosforilação Oxidativa PROFESSORA : ADRIANNE MENDONÇA
  2. 2. Funções do Ciclo,-Gerar ATP, coenzimas reduzidas-“Gerar” intermediários para vias biossínteses-Ciclo é estágio final de várias vias
  3. 3. Complexo piruvato dehidrogenase
  4. 4. TPP ↓ Grupo reativo ↓ Grupo reativo ↓ carbanion carbanion
  5. 5. Acetyl CoA+Oxaloacetate to Citrate Citrate synthaseEnzyme:Reaction: CondensationAcetyl CoA condenses with oxaloacetate first,to form citryl CoA. Then citryl CoA ishydrolyzed to citrate and CoA.Prosthetic group: No
  6. 6. Citrate to cis-AconitateEnzyme: AconitaseReaction: DehydrationCitrate is isomerized to isocitrate by this first dehydration and yields cis-aconitate as an intermediate.Prosthetic group: Fe-S
  7. 7. cis-Aconitate to IsocitrateEnzyme: AconitaseReaction: HydrationHydration of cis-aconitate gives the interchange of H atom and OH group from the step 2.Prosthetic group: Fe-S
  8. 8. Isocitrate to alpha-KetoglutarateEnzyme: Isocitrate dehydrogenaseReaction: Oxidative decarboxylationDehydrogenation of isocitrate occurs and yields oxalosuccinate as an intermediate.ThenCO2 leaves to have alpha-ketoglutarate.This reaction gives NADH.Prosthetic group: No
  9. 9. alpha-Ketoglutarate to Succinyl CoAEnzyme: alpha-Ketoglutarate dehydrogenase complexReaction: Oxidative decarboxylationThis mechanism is almost as same as the reaction of the oxidativedecarboxylation of pyruvate to acetyl CoA by pyruvate dehydrogenase complex.This reaction gives one NADH.Prosthetic group: Lipoic acid, FAD, TPP
  10. 10. Succinyl CoA to SuccinateEnzyme: Succinyl CoA synthetaseReaction: Substrate-level phosphorylationThe thioester bond of succinyl and CoA is an energy rich bond. Thus only this step gives ahigh-energy phosphate compound,GTP from the couple reactions of the thioester bondcleavage and the phosphorylation of GDP.Prosthetic group:No GTP + ADP → GDP + ATP
  11. 11. Succinate to FumarateEnzyme: Succinate dehydrogenaseReaction: OxidationThe two hydrogens of succinate leave to an acceptor, FAD. Then this reaction yields fumarate andFADH2.Prosthetic group: FAD & Fe-S
  12. 12. Fumarato → l-MalatoFumarase
  13. 13. Malate to OxaloacetateEnzyme: Malate dehydrogenaseReaction: OxidationMalate is dehydrogenated to form oxaloacetate. The hydrogen acceptor is NAD. So this reactionyields NADH.Prosthetic group: No
  14. 14. 1 cal~ 4 Joules
  15. 15. Note AcetilCoA é na prática queimado no ciclo,Os intermediários do ciclo não são!!
  16. 16. Elementos necessários ao TCA, reações anapleróticas repõem intermediários do Krebs.
  17. 17. Repor ciclo para funcionar
  18. 18.
  19. 19. Bactérias e plantas
  20. 20. 2 Ac CoA + NAD+ + 2 H2O  Succinato + 2 CoA +
  21. 21. Fosforilação Oxidativa
  22. 22. ∆Go = -nℑ∆Eo
  23. 23. Fe3+ + e- → Fe2+ 0.771NO3-+2 H++2 e- → NO2-+H2O 0.421Cytochrome f( Fe3+)+ e- → cytochrome f(Fe2+) 0.365Cytochrome a3( Fe3+)+ e- → cytochrome a3(Fe2+) 0.350Cytochrome a(Fe3+)+ e- → cytochrome a(Fe2+) 0.290Cytochrome c( Fe3+)+ e - → cytochrome c(Fe2+) 0.254Cytochrome c1( Fe3+)+ e - → cytochrome c1(Fe2+) 0.220UQH ⋅ + H1 + e- → UQH2 (UQ=coenzyme Q) 0.190UQ + 2 H+ + 2 e- → UQH2 0.060Cytochrome bH(Fe3+) + e - → cytochrome bH(Fe2+) 0.050Fumarate + 2 H+ + 2 e- → succinate 0.031UQ + H+ + e- → UQH ⋅ 0.030Cytochrome b5( Fe3+)+ e - → cytochrome b5(Fe2+) 0.020[FAD]+2 H++2 e- → [FADH2] 0.003-0.091*Cytochrome bL( Fe3+)+ e - → cytochrome bL(Fe2+) -0.100Oxaloacetate + 2 H+ + 2 e- → malate -0.166Pyruvate + 2 H+ + 2 e- → lactate -0.185
  24. 24. FAD + 2 H+ + 2 e- → FADH2 -0.219NAD+ + 2 H+ + 2 e- → NADH + H+ -0.320NADP+ + 2 H+ + 2 e- → NADPH + H+ -0.320
  25. 25. Figure 21.29 · The structures of several inhibitors of electron transport and
  26. 26. F
  27. 27. F
  28. 28. OBRIGADA !!!

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