Txhua cov tshuaj lom neeg biochemical hauv cov hlwb ntawm txhua yam kabmob ua haujlwm nrog kev siv zog. Cov kab mob ua pa yog ib ntu ntawm cov qauv tshwj xeeb uas nyob rau hauv daim nyias nyias ntawm mitochondria thiab ua haujlwm los tsim ATP. Adenosine triphosphate yog lub zog thoob ntiaj teb thiab tuaj yeem sib sau hauv nws tus kheej los ntawm 80 txog 120 kJ.
Lub tshuab pa hluav taws xob - nws yog dab tsi?
Electrons thiab protons ua lub luag haujlwm tseem ceeb hauv kev tsim lub zog. Lawv tsim muaj qhov sib txawv ntawm qhov sib txawv ntawm cov mitochondrial membrane, uas ua rau muaj kev taw qhia txav ntawm cov khoom - tam sim no. Cov saw hlau ua pa (aka ETC, electron thauj saw) kho qhov kev hloov pauv ntawm cov khoom muaj txiaj ntsig zoo rau hauv qhov chaw nruab nrab thiab cov khoom tsis zoo rau hauv cov tuab ntawm cov mitochondrial membrane.
Lub luag haujlwm tseem ceeb hauv kev tsim lub zog yog ATP synthase. Qhov complex no hloov lub zog ntawm kev taw qhia ntawm protons mus rau hauv lub zog ntawm biochemical bonds. Los ntawm txoj kev, yuav luag zoo tib yam complex muaj nyob rau hauv cov nroj tsuag chloroplasts.
Complexes thiab enzymes ntawm txoj hlab pa
Kev hloov ntawm electrons yog nrog los ntawm biochemical cov tshuaj tiv thaiv nyob rau hauv lub xub ntiag ntawm ib tug enzymatic apparatus. Cov tshuaj lom neeg lom neeg no, ntau cov ntawv luam uas tsim cov qauv loj, ua tus neeg nruab nrab hauv kev hloov ntawm electrons.
Txoj hauv kev ua pa ntawm txoj hlab pa yog cov khoom nruab nrab ntawm kev thauj cov khoom them nqi. Nyob rau hauv tag nrho, muaj 4 xws formations nyob rau hauv lub puab membrane ntawm mitochondria, raws li zoo raws li ATP synthase. Tag nrho cov qauv no tau koom ua ke los ntawm ib lub hom phiaj - kev hloov ntawm electrons raws ETC, kev hloov ntawm hydrogen protons mus rau hauv qhov chaw nruab nrab thiab, vim li ntawd, kev sib txuas ntawm ATP.
Cov complex yog qhov sib xyaw ntawm cov protein molecules, ntawm cov uas muaj enzymes, cov qauv thiab cov teeb liab proteins. Txhua ntawm 4 complexes ua nws tus kheej muaj nuj nqi, tsuas yog peculiar rau nws. Wb saib seb cov hauj lwm dab tsi cov qauv no muaj nyob hauv ETC.
I complex
Cov kab mob ua pa ua lub luag haujlwm tseem ceeb hauv kev hloov pauv ntawm cov hluav taws xob hauv cov tuab ntawm mitochondrial membrane. Cov kev cuam tshuam ntawm abstraction ntawm hydrogen protons thiab lawv cov khoom siv hluav taws xob yog ib qho ntawm cov kev cuam tshuam hauv nruab nrab ETC. Thawj txoj hauv kev thauj mus los yuav siv cov molecules ntawm NADH + (hauv tsiaj) lossis NADPH + (hauv cov nroj tsuag) ua raws li kev tshem tawm ntawm plaub hydrogen protons. Qhov tseeb, vim yog cov tshuaj tiv thaiv biochemical no, complex kuv kuj hu ua NADH - dehydrogenase (tom qab lub npe ntawm lub hauv paus enzyme).
Cov muaj pes tsawg leeg ntawm dehydrogenase complex suav nrog 3 hom hlau-sulfur proteins, nrog rauFlavin mononucleotides (FMN).
II complex
Kev ua haujlwm ntawm qhov kev ua haujlwm no tsis cuam tshuam nrog kev hloov pauv ntawm hydrogen protons mus rau qhov chaw nruab nrab. Lub luag haujlwm tseem ceeb ntawm cov qauv no yog muab cov khoom siv hluav taws xob ntxiv rau cov saw hlau thauj hluav taws xob los ntawm oxidation ntawm succinate. Lub hauv paus enzyme ntawm lub complex yog succinate-ubiquinone oxidoreductase, uas catalyzes tshem tawm ntawm electrons los ntawm succinic acid thiab hloov mus rau lipophilic ubiquinone.
Tus xa khoom ntawm hydrogen protons thiab electrons rau qhov thib ob tseem yog FADН 2. Txawm li cas los xij, qhov ua tau zoo ntawm flavin adenine dinucleotide tsawg dua li ntawm nws cov analogues - NADH lossis NADPH.
Complex II suav nrog peb hom hlau-sulfur proteins thiab lub hauv paus enzyme succinate oxidoreductase.
III complex
Cov khoom txuas ntxiv, ETC, muaj cytochromes b 556, b 560 thiab c1, nrog rau cov hlau-sulfur protein Riske. Kev ua haujlwm ntawm qhov thib peb yog txuam nrog kev hloov ntawm ob lub hydrogen protons rau hauv qhov chaw nruab nrab, thiab cov hluav taws xob los ntawm lipophilic ubiquinone rau cytochrome C.
Qhov peculiarity ntawm Riske protein yog tias nws yaj hauv cov rog. Lwm cov proteins ntawm pab pawg no, uas tau pom nyob rau hauv cov kab mob ua pa nyuaj, yog dej-soluble. Qhov no feature cuam tshuam txoj hauj lwm ntawm cov protein molecules nyob rau hauv lub thickness ntawm lub puab membrane ntawm mitochondria.
Qhov thib peb txoj haujlwm ua ubiquinone-cytochrome c-oxidoreductase.
IV complex
Nws kuj yog cytochrome-oxidant complex, yog qhov kawg taw tes hauv ETC. Nws txoj haujlwm yog uaelectron hloov ntawm cytochrome c rau oxygen atoms. Tom qab ntawd, tsis zoo them O atoms yuav hnov mob nrog hydrogen protons los ua dej. Lub ntsiab enzyme yog cytochrome c-oxygen oxidoreductase.
Plaub txoj kev suav nrog cytochromes a, 3 thiab ob lub atoms tooj liab. Cytochrome a3 ua lub luag haujlwm tseem ceeb hauv kev hloov hluav taws xob mus rau oxygen. Kev sib cuam tshuam ntawm cov qauv no yog suppressed los ntawm nitrogen cyanide thiab carbon monoxide, uas nyob rau hauv lub ntiaj teb no kev txiav txim siab ua rau lub cessation ntawm ATP synthesis thiab tuag.
YUbiquinone
Ubiquinone yog ib yam khoom zoo li cov vitamin, ib qho lipophilic compound uas txav mus los hauv cov tuab ntawm daim nyias nyias. Lub mitochondrial respiratory saw tsis tuaj yeem ua yam tsis muaj cov qauv no, vim nws yog lub luag haujlwm rau kev thauj cov electrons los ntawm complexes I thiab II mus rau complex III.
Ubiquinone yog benzoquinone derivative. Cov qauv no hauv cov duab kos tuaj yeem txhais tau los ntawm tsab ntawv Q lossis luv luv li LU (lipophilic ubiquinone). Oxidation ntawm lub molecule ua rau tsim ntawm semiquinone, ib tug muaj zog oxidizing tus neeg sawv cev uas muaj feem xyuam rau lub cell.
ATP synthase
Lub luag haujlwm tseem ceeb hauv kev tsim lub zog yog ATP synthase. Cov qauv zoo li cov nceb no siv lub zog ntawm kev txav mus los ntawm cov khoom (protons) los hloov nws mus rau hauv lub zog ntawm cov khoom siv tshuaj lom neeg.
Cov txheej txheem tseem ceeb uas tshwm sim thoob plaws hauv ETC yog oxidation. Cov kab mob ua pa yog lub luag haujlwm rau kev hloov ntawm electrons nyob rau hauv lub thickness ntawm mitochondrial membrane thiab lawv tsub zuj zuj nyob rau hauv lub matrix. Ib txhijcomplexes I, III thiab IV twj tso kua mis hydrogen protons rau hauv qhov chaw nruab nrab. Qhov sib txawv ntawm cov nqi ntawm ob sab ntawm daim nyias nyias ua rau kev taw qhia txav ntawm protons los ntawm ATP synthase. Yog li H + nkag mus rau hauv matrix, ntsib electrons (uas yog txuam nrog oxygen) thiab tsim ib yam khoom uas nruab nrab rau ntawm tes - dej.
ATP synthase muaj F0 thiab F1 subunits, uas ua ke tsim ib lub router molecule. F1 yog tsim los ntawm peb alpha thiab peb beta subunits, uas ua ke ua ib lub channel. Cov channel no muaj tib txoj kab uas hla raws li hydrogen protons. Thaum cov khoom siv tau zoo dhau los ntawm ATP synthase, lub taub hau ntawm F0 molecule tig 360 degrees nyob ib ncig ntawm nws axis. Lub sijhawm no, phosphorus residues txuas nrog AMP lossis ADP (adenosine mono- thiab diphosphate) siv cov khoom siv hluav taws xob siab, uas muaj ntau lub zog.
ATP synthases muaj nyob hauv lub cev tsis yog hauv mitochondria nkaus xwb. Hauv cov nroj tsuag, cov complexes tseem nyob ntawm lub vacuole membrane (tonoplast), nrog rau ntawm thylakoids ntawm chloroplast.
Tsis tas li, ATPase muaj nyob hauv cov tsiaj thiab cov nroj tsuag. Lawv muaj cov qauv zoo sib xws rau ATP synthases, tab sis lawv qhov kev ua yog tsom rau kev tshem tawm cov phosphorus residues nrog kev siv zog.
Lub ntsiab lus lom neeg ntawm txoj hlab pa
Ua ntej, cov khoom kawg ntawm ETC cov tshuaj tiv thaiv yog cov dej metabolic (300-400 ml ib hnub). Qhov thib ob, ATP yog synthesized thiab lub zog yog khaws cia rau hauv biochemical bonds ntawm no molecule. 40-60 yog synthesized ib hnubkg ntawm adenosine triphosphate thiab tib tus nqi yog siv nyob rau hauv cov tshuaj enzymatic ntawm tes. Lub neej ntawm ib qho ATP molecule yog 1 feeb, yog li cov kab mob ua pa yuav tsum ua haujlwm zoo, meej thiab tsis muaj qhov yuam kev. Txwv tsis pub, lub xov tooj yuav tuag.
Mitochondria raug suav tias yog lub zog ntawm txhua lub xovtooj. Lawv tus lej nyob ntawm kev siv lub zog uas tsim nyog rau qee yam haujlwm. Piv txwv li, txog li 1000 mitochondria tuaj yeem suav rau hauv cov neurons, uas feem ntau tsim ib pawg hauv lub npe hu ua synaptic plaque.
Qhov txawv ntawm cov kab ua pa hauv cov nroj tsuag thiab tsiaj
Nyob hauv cov nroj tsuag, chloroplast yog ib qho ntxiv "chaw nres tsheb hluav taws xob" ntawm tes. ATP synthases kuj pom muaj nyob rau hauv daim nyias nyias ntawm cov organelles, thiab qhov no yog ib qho zoo dua cov tsiaj hlwb.
Nroj tsuag tseem tuaj yeem muaj sia nyob siab ntawm carbon monoxide, nitrogen thiab cyanide los ntawm txoj kev cyanide-resistant hauv ETC. Cov kab mob ua pa yog li xaus ntawm ubiquinone, cov electrons uas tam sim ntawd hloov mus rau oxygen atoms. Yog li ntawd, ATP tsawg dua yog synthesized, tab sis cov nroj tsuag muaj peev xwm muaj sia nyob tsis zoo. Tsiaj txhu nyob rau hauv cov xwm txheej zoo li no tuag nrog rau lub sijhawm ntev.
Koj tuaj yeem sib piv qhov ua tau zoo ntawm NAD, FAD, thiab txoj hauv kev tiv thaiv cyanide los ntawm kev siv tus nqi ntawm ATP ntau lawm ib qho hluav taws xob hloov.
- nrog NAD lossis NADP, 3 ATP molecules raug tsim;
- FAD tsim 2 ATP molecules;
- cyanide-resistant txoj kev tsim 1 ATP molecule.
Evolutionary tus nqi ntawm ETC
Rau tag nrho cov kab mob eukaryotic, ib qho ntawm lub zog tseem ceeb yog cov kab ua pa. Lub biochemistry ntawm ATP synthesis nyob rau hauv lub cell muab faib ua ob hom: substrate phosphorylation thiab oxidative phosphorylation. ETC yog siv rau hauv kev sib txuas ntawm lub zog ntawm hom thib ob, piv txwv li vim yog cov tshuaj tiv thaiv redox.
Hauv cov kab mob prokaryotic, ATP tsuas yog tsim nyob rau hauv cov txheej txheem ntawm substrate phosphorylation ntawm theem ntawm glycolysis. Rau-carbon suab thaj (feem ntau yog cov piam thaj) koom nrog hauv lub voj voog ntawm cov tshuaj tiv thaiv, thiab ntawm qhov tso zis ntawm tes tau txais 2 ATP molecules. Hom kev sib txuas ntawm lub zog no yog suav tias yog qhov qub tshaj plaws, txij li hauv eukaryotes 36 ATP molecules tau tsim nyob rau hauv cov txheej txheem ntawm oxidative phosphorylation.
Txawm li cas los xij, qhov no tsis tau txhais hais tias cov nroj tsuag niaj hnub thiab tsiaj txhu tau poob lub peev xwm los ua cov phosphorylation substrate. Nws tsuas yog hais tias hom ATP synthesis no tau dhau los ua ib qho ntawm peb theem ntawm kev tau txais lub zog hauv lub cell.
Glycolysis hauv eukaryotes tshwm sim hauv cytoplasm ntawm lub cell. Muaj tag nrho cov enzymes tsim nyog uas tuaj yeem zom cov piam thaj rau hauv ob lub molecules ntawm pyruvic acid nrog kev tsim ntawm 2 molecules ntawm ATP. Tag nrho cov theem tom ntej no tshwm sim hauv mitochondrial matrix. Lub voj voog Krebs, lossis tricarboxylic acid voj voog, kuj tshwm sim hauv mitochondria. Qhov no yog cov saw kaw ntawm cov tshuaj tiv thaiv, raws li qhov tshwm sim ntawm NADH thiab FADH2 raug tsim. Cov molecules yuav mus raws li consumables rau ETC.
