Phosphorylation ya okosijeni: Kutumiza kwa Electron ndi Chemiosmosis
Kuchuluka kwa okosijeni m'thupi ndi njira yofunika kwambiri pa kagayidwe ka maselo komwe kumachitika mu mitochondria. Njira imeneyi imapangitsa kuti adenosine triphosphate (ATP) yambiri ipangidwe, molekyulu yomwe imapereka mphamvu pazochitika zosiyanasiyana za biochemical m'maselo. Kuchuluka kwa okosijeni m'thupi kumakhala ndi magawo awiri akuluakulu: unyolo woyendera ma elekitironi ndi chemiosmosis. Zonsezi zimagwirira ntchito limodzi kuti zisinthe mphamvu kuchokera ku michere yomwe yadyedwa kukhala mitundu yamphamvu yogwiritsidwa ntchito m'maselo.
Kuyendera kwa Ma Electron
Kutumiza ma elekitironi kumachitika mu nembanemba yamkati ya mitochondrial. Nembanemba iyi ili ndi mapuloteni asanu omwe amagwira ntchito limodzi kuti asunthe ma elekitironi kuchokera kwa opereka ma elekitironi monga NADH ndi FADH2 kupita ku cholandirira ma elekitironi chomaliza, mpweya. Njirayi imatulutsa mphamvu, yomwe imagwiritsidwa ntchito kupopera ma protoni (H+) kudutsa nembanemba ya mitochondrial kuchokera ku matrix kupita ku malo apakati pa nembanemba, ndikupanga gradient ya protoni.
Complex I: NADH-Dehydrogenase
Njira yotumizira ma elekitironi imayamba mu Complex I, yomwe imadziwikanso kuti NADH dehydrogenase. NADH yopangidwa mu Krebs cycle imapereka ma elekitironi ku complex iyi. Ma elekitironi amasamutsidwa kudzera mu ma cofactor angapo, kuphatikiza FMN (flavin mononucleotide) ndi magulu angapo a iron-sulfur. Panthawiyi, ma proton anayi amapopedwa kuchokera ku matrix kupita ku malo apakati.
Complex II: Succinate Dehydrogenase
Complex II ndi succinate dehydrogenase, yomwe imagwiranso ntchito mu Krebs cycle. Complex iyi imalandira ma elekitironi kuchokera ku FADH2, imapanga FAD, ndikutulutsa ma elekitironi ku ubiquinone (coenzyme Q). Mosiyana ndi Complex I, Complex II sipompa ma protoni kudutsa nembanemba ya mitochondrial.
Chovuta Chachitatu: Cytochrome bc1
Complex III, kapena cytochrome bc1, imalandira ma elekitironi ochokera ku ubiquinol (ubiquinone wochepetsedwa) ndikusamutsa ku cytochrome c, puloteni yaying'ono yosungunuka mu danga la pakati pa membrane. Complex III imathandizanso kupopera ma protoni mu danga la pakati pa membrane, ndikuwonjezera ku gradient ya proton yomwe yakhazikitsidwa.
Complex IV: Cytochrome c Oxidase
Complex IV, kapena cytochrome c oxidase, ndiye gawo lomaliza mu unyolo woyendera ma elekitironi. Ma elekitironi amasamutsidwa kuchokera ku cytochrome c kupita ku mpweya, womwe ndi wolandila ma elekitironi omaliza, ndikupanga madzi. Njirayi imatsagananso ndi kupopera ma protoni kulowa mu malo apakati pa membrane.
Udindo wa Ubiquinone ndi Cytochrome c
Ubiquinone ndi cytochrome c zimagwira ntchito ngati zonyamulira ma elekitironi zoyenda. Ubiquinone imatenga ma elekitironi kuchokera ku Complexes I ndi II kenako nkuwapereka ku Complex III. Pakadali pano, cytochrome c imanyamula ma elekitironi kuchokera ku Complex III kupita ku Complex IV, zomwe zimathandiza kuti njira yotumizira ma elekitironi ipitirire bwino.
Chemiosmosis
Chemiosmosis ndi njira yomwe imagwiritsa ntchito ma proton gradient omwe amapangidwa panthawi yotumiza ma elekitironi kuti apange ATP. Njirayi imayendetsedwa ndi ATP synthase, enzyme yomwe ili mkati mwa nembanemba ya mitochondrial.
Proton Gradient ndi ATP Synthase
Kuchuluka kwa ma proton komwe kumachitika panthawi yoyendetsa ma elekitironi kumapanga mphamvu yamagetsi yomwe nthawi zambiri imatchedwa mphamvu ya proton-motive. Mphamvu imeneyi imayendetsa ma proton kubwerera ku mitochondrial matrix kudzera mu ATP synthase, yomwe imagwiritsa ntchito kayendedwe kameneka kusintha ADP ndi inorganic phosphate kukhala ATP.
Kapangidwe ndi Ntchito ya ATP Synthase
ATP synthase ili ndi magawo awiri akuluakulu: F0 ndi F1. F0 imapanga njira ya proton kudutsa nembanemba ya mitochondrial, pomwe F1 imagwira ntchito ngati malo othandizira kupanga ATP. Kuyenda kwa ma proton kudzera mu F0 kumapangitsa kuti gawo la F1 lizizungulira, zomwe zimapangitsa kuti kusintha kwa mawonekedwe kukhale kofunikira kuti kumangirire ADP ndi phosphate, ndikupanga ATP.
Kulamulira ndi Kuchita Bwino kwa Oxidative Phosphorylation
Njira ya okosijeni phosphorylation imayendetsedwa ndi zosowa za mphamvu zamaselo. ATP, ADP, ndi phosphate yopanda organic imagwira ntchito yofunika kwambiri pakuwongolera kumeneku. Kuchuluka kwa ATP kumachedwetsa njirayi, pomwe kuchuluka kwa ADP kumayipangitsa kuti izi zichedwetse.
Kugwira ntchito bwino kwa phosphorylation ya okosijeni ndikofunikanso. Molekyulu iliyonse ya NADH yomwe imasungunuka mu unyolo wonyamula ma elekitironi imatha kupanga pafupifupi 2.5 ATP, pomwe FADH2 imapanga pafupifupi 1.5 ATP. Ngakhale kuti si yogwira ntchito bwino 100%, phosphorylation ya okosijeni ndiye gwero lalikulu la kupanga ATP m'maselo a aerobic.
Zotsatira Zachipatala
Kulephera kugwira ntchito bwino kwa phosphorylation ya okosijeni kungayambitse matenda osiyanasiyana a mitochondrial, omwe nthawi zambiri amakhudza ziwalo zomwe zimafuna mphamvu zambiri, monga minofu ndi ubongo. Matendawa amatha kuchitika chifukwa cha kusintha kwa majini kapena zinthu zina zakunja, monga poizoni zomwe zimalepheretsa unyolo woyendera ma elekitironi.
Mwachitsanzo, cyanide ndi carbon monoxide zimaletsa Complex IV, zomwe zimaletsa kuyenda kwa ma elekitironi ndi kupanga ATP, zomwe zimapangitsa kuti minofu yofunika kwambiri ya ziwalo iwonongeke chifukwa cha kusowa mphamvu.
Mapeto
Kuchuluka kwa okosijeni m'thupi ndi njira yofunika kwambiri yomwe imagwiritsa ntchito mayendedwe a ma elekitironi ndi chemiosmosis kuti ipange ATP, yomwe ndi chonyamulira chachikulu cha mphamvu m'maselo. Kumvetsetsa momwe imagwirira ntchito sikuti ndikofunikira kokha pa biology yoyambira komanso kumatsegula chitseko chopangira njira zochizira matenda okhudzana ndi vuto la kagayidwe kachakudya kameneka. Kupitiliza kufufuza mbali za mamolekyu a okosijeni m'thupi kudzathandiza ofufuza kupeza njira zatsopano zothetsera mavuto azaumoyo wa anthu.
