Cyclus acidi citrici

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Cursus cycli acidi citrici

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.

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 triclyclicorum" 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.

Cursus[recensere | fontem recensere]

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 generatur, sed generantur GTP et CO2. Oxygenium quidem, ut ATP, demum in itinere proximo, phosphorylatione oxydativa, momenta maxima habebit.

Condiciones[recensere | fontem recensere]

Gradus cycli acidi citrici[recensere | fontem recensere]

  • Reactio biochemica 0/10 (Citrati synthasis): Oxaloacetatum + Acetylo-CoA + H2O → Citratum + 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

Eventus[recensere | fontem recensere]

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

Notae[recensere | fontem recensere]

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

Nexus interni

Nexus externi[recensere | fontem recensere]

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