Cyclus acidi citrici vel cylcus acidorum triclyclicorum vel cyclus Krebs est iter metabolicum intracellulare et iter paenultimum in mitochondriis, ante phosphorylationem oxydativam enim, energiam cellularem (ATP) generantem.

Cursus cycli acidi citrici

Cyclus ex pyruvato et, non exigue, aqua generat duo substantias, electrona e- in proximum iter portantes: NADH+H+ et FAD(2H).

Hic cyclus anno 1937 ab Iohanne Adolpho Krebs primo descriptus est; nimirum Krebs anno 1953 praemium Nobelianum physiologiae et medicinae addictum est[1]. Hac de causa cyclus non raro "cyclus Krebs" appellatur. Praeterea nomen "cycli acidorum tricyclicorum" de tribus acidis tricyclicis intra cyclum Krebs (citrato, aconitato, isocitrato) partibus cursus cycli sumitur; denique nomen "cycli acidi citrici" de molecula acidi citrici, non electrice onerati, derivatur, quamquam citratum forma electrice onerata partem cycli ipsius capit.

CursusRecensere

Aequatio generalis cycli Krebs:

Acetylo-CoA + 3 NAD+ + FAD + GDP + Pi+ 2 H2O → CoA + 3 NADH + 3 H+ + FAD(2H) + GTP + 2 CO2

Nota cycli Krebs ope, nec oxygenium consumatur, nec ATP generetur, sed generentur GTP et CO2. Oxygenium quidem, ut ATP, demum in itinere proximo, phosphorylatione oxydativa, momenta maxima habebit.

CondicionesRecensere

Gradus cycli acidi citriciRecensere

  • Reactio biochemica 0/10 (Citrati synthasis): Oxaloacetatum + Acetylo-CoA + H2OCitratum + CoA-SH
  • Reactio biochemica 1 (Aconitasis): Citratum + CoA-SH → cis-Aconitatum + H2O
  • Reactio biochemica 2 (Aconitasis): cis-Aconitatum + H2O → Isocitratum
  • Reactio biochemica 3 (Isocitrati dehydrogenasis): Isocitratum + NAD+ → Oxalosuccinatum + NADH + H+
  • Reactio biochemica 4 (Isocitrati dehydrogenasis): Oxalosuccinatum → α-Ketoglutaratum + CO2
  • Reactio biochemica 5 (α-Ketoglutarate dehydrogenasis): α-Ketoglutaratum + NAD+ + CoA-SH → Succinylo-CoA + NADH + H+ + CO2
  • Reactio biochemica 6 (Succinylo-CoA synthetasis): Succinylo-CoA + GDP + Pi → Succinatum + CoA-SH + GTP
  • Reactio biochemica 7 (Succinati dehydrogenasis): Succinatum + Ubiquinonum (Q) → Fumaratum + Ubiquilonum (QH2)
  • Reactio biochemica 8 (Fumarasis): Fumaratum + H2OL-Malatum
  • Reactio biochemica 9 (Malati dehydrogenasis) L-Malatum + NAD+ → Oxaloacetatum + NADH + H+
  • Reactio biochemica 10/0 (Citrati synthasis): Oxaloacetatum + Acetylo-CoA + H2O → Citratum + CoA-SH

EventusRecensere

  • Electrona (cyclo 3 moleculae NADH+H+, 1 molecula FAD(2H))
  • GTP (cyclo 1 molecula)
  • CO2 (cyclo 2 moleculae, aeris exspirati)

NotaeRecensere

  1. De Iohanne Adolpho Krebs in situ praemio Nobeliano medicinae dicato (Anglice)

Nexus interni

Nexus externiRecensere

  Haec stipula ad biologiam spectat. Amplifica, si potes!