Ngitshele kafushane ukuthi umjikelezo we-citric acid usebenza kanjani
Context:Umjikelezo we-citric acid (CAC) - owaziwa nangokuthi umjikelezo we-Krebs, umjikelezo we-Szent-Györgyi-Krebs noma umjikelezo we-TCA (umjikelezo we-tricarboxylic acid) - uchungechunge lwezimpendulo zamakhemikhali ukukhulula amandla agciniwe ngokusebenzisa i-oxidation ye-acetyl-CoA etholakala kuma-carbohydrate, amafutha namaprotheni. Umjikelezo kaKrebs usetshenziswa yizinto eziphilayo eziphefumulayo (ngokuphambene nezinto eziphilayo ezivutshwayo) ukukhiqiza amandla, kungaba ngokuphefumula kwe-anaerobic noma ukuphefumula kwe-aerobic. Ngaphezu kwalokho, umjikelezo unikeza izandulela zama-amino acid athile, kanye ne-ejenti yokunciphisa i-NADH, esetshenziswa kwezinye izinto eziningi. Ukubaluleka kwayo okukhulu ezindleleni eziningi zamakhemikhali abonisa ukuthi kwakungenye yezingxenye zokuqala ze-metabolism futhi kungenzeka ukuthi yavela abiogenically. Ngisho noma kuthiwa "umjikelezo", akudingekile ukuba ama-metabolite alandele indlela eyodwa kuphela; okungenani izingxenye ezintathu ezihlukile zomjikelezo we-citric acid ziye zaqashelwa.  Igama lale ndlela ye-metabolic lisuselwa ku-citric acid (i-tricarboxylic acid, evame ukubizwa ngokuthi i-citrate, njengoba ifomu le-ionized libusa ku-pH yemvelo) edliwayo bese ivuselelwa ngalolu chungechunge lwezimpendulo ukuqedela umjikelezo. Umjikelezo udla i-acetate (ngesimo se-acetyl-CoA) namanzi, wehlisa i-NAD + ibe yi-NADH, ikhiphe isikhutha. I-NADH ekhiqizwa umjikelezo we-citric acid ifakwa endleleni ye-oxidative phosphorylation (ukuthuthwa kwama-electron). Umphumela walezi zindlela ezimbili ezihlobene eduze uwukwakheka kwezakhi ukuze kukhiqizwe amandla amakhemikhali asetshenziswayo ngesimo se-ATP.  Kumangqamuzana e - eukaryotic, umjikelezo we - citric acid wenziwa ngaphakathi kwe - matrix ye - mitochondrion. Kumangqamuzana e-prokaryotic, njengama-bacterium, angenayo i-mitochondria, ukulandelana kokuphendula kwe-citric acid cycle kwenziwa ku-cytosol ne-proton gradient yokukhiqizwa kwe-ATP enqamula ebusweni beselula (i-plasma membrane) kunokuba i-membrane yangaphakathi ye-mitochondrion.  Kumangqamuzana e-pyruvate ngayinye (evela ku-glycolysis), isivuno esiphelele samakhompiyutha aqukethe amandla avela kumjikelezo we-citric acid yi-NADH emithathu, i-FADH2 eyodwa, ne-GTP eyodwa.
Umjikelezo we-citric acid usetshenziswa yizinto eziphilayo ukuze zikhiqize amandla. Lokhu kufezwa ngochungechunge lwezimpendulo zamakhemikhali ezenzeka kuma-mitochondria ukuze kukhishwe amandla agciniwe ngokwenziwa kwe-acetyl-CoA etholakala kumafutha, amaprotheni, nama-carbohydrate.