Cyclus acidi citrici

Cursus cycli acidi citrici

Cyclus acidi citrici vel cylcus acidorum triclyclicorum vel tricarboxylici acidi cyclus 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. 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.

Cursus

Aequatio generalis cycli Krebs:

Acetylo-CoA 3 NAD FAD GDP P_i 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.

Condiciones

• Substrata pyruvatum generantia
• Aqua (cyclo 2 moleculae)
• Mitochondria sana

Gradus cycli acidi citrici

• 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 P_i → Succinatum CoA-SH GTP
• Reactio biochemica 7 (Succinati dehydrogenasis): Succinatum Ubiquinonum (Q) → Fumaratum Ubiquilonum (QH₂)
• Reactio biochemica 8 (Fumarasis): Fumaratum H₂O → L-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

• Electrona (cyclo 3 moleculae NADH H , 1 molecula FAD(2H))
• GTP (cyclo 1 molecula)
• CO₂ (cyclo 2 moleculae, aeris exspirati)
• Succinylo coenzymum A in parte in synthesem porphyrini defertur.

Plura legere si cupis

• Jean-Jacques Brière 1, Judith Favier, Anne-Paule Gimenez-Roqueplo, Pierre Rustin. "Tricarboxylic acid cycle dysfunction as a cause of human diseases and tumor formation", Review Am J Physiol Cell Physiol, 2006ː C1114-C1120
• Gray, L.R., Tompkins, S.C. & Taylor, E.B. "Regulation of pyruvate metabolism and human disease". Cell. Mol. Life Sci., 2014ː 2577–2604
• Oliver E. Owen, Satish C. Kalhan, Richard W. Hanson. "The key role of Anaplerosis and Cataplerosis for Citric Acid Cycle Function", The Journal of biological Chemistry, 2002ː 30409-30412
• Mulchand S. Patel, Natalia S. Nemeria, William Furey and Frank Jordan. "The Pyruvate Dehydrogenase Complexes: Structure-based Function and Regulation", Journal of biological Chemistry, 2014: 16615–16623

Nexus interni

• Acidum fumaricum
• Energia
• Mitochondrium

Nexus externi

• Khan academy de cycli acidi citrici. (Anglice)
• Alii cursus cycli Krebs. (Anglice)

stipula

Haec stipula ad biologiam spectat. Amplifica, si potes!