Yuav kom tib neeg lub cev muaj lub neej zoo, nws tau tsim cov txheej txheem rau kev tshem tawm cov tshuaj lom. Ntawm lawv, ammonia yog qhov kawg khoom ntawm cov metabolism hauv nitrogenous tebchaw, feem ntau cov proteins. NH3 yog tshuaj lom rau lub cev thiab, zoo li txhua yam tshuaj lom, raug tso tawm los ntawm cov txheej txheem excretory. Tab sis ua ntej ammonia tau dhau los ua cov tshuaj tiv thaiv zoo, uas yog hu ua lub voj voog ornithine.
Ntaus cov metabolism hauv nitrogen
Tsis yog txhua tus tsiaj tso ammonia rau hauv ib puag ncig. Lwm cov khoom kawg ntawm nitrogen metabolism yog uric acid thiab urea. Raws li, peb hom nitrogen metabolism raug hu ua, nyob ntawm cov khoom tso tawm.
Ammoniotelic yam. Cov khoom kawg ntawm no yog ammonia. Nws yog ib qho tsis muaj xim tsis muaj roj soluble hauv dej. Ammoniothelia yog tus yam ntxwv ntawm txhua tus ntses uas nyob hauv dej ntsev.
Ureotelic yam. Tsiaj txhu uas yog tus cwj pwm los ntawm ureothelia tso urea rau hauv ib puag ncig. Piv txwv yogntses dej qab zib, amphibians thiab tsiaj txhu, suav nrog tib neeg.
Uricotelic yam. Qhov no suav nrog cov neeg sawv cev ntawm cov tsiaj ntiaj teb, uas qhov kawg metabolite yog uric acid crystals. Cov tshuaj no yog cov khoom ntawm nitrogen metabolism hauv cov noog thiab cov tsiaj reptiles.
Nyob rau hauv ib qho ntawm cov xwm txheej no, lub luag haujlwm ntawm cov khoom kawg ntawm cov metabolism yog tshem tawm cov nitrogen uas tsis tsim nyog los ntawm lub cev. Yog tias qhov no tsis tshwm sim, kev sau se ntawm tes thiab inhibition ntawm cov tshuaj tiv thaiv tseem ceeb raug pom.
YUrea yog dab tsi?
Urea yog ib qho amide ntawm carbonic acid. Nws yog tsim los ntawm ammonia, carbon dioxide, nitrogen thiab amino pawg ntawm tej yam tshuaj thaum lub sij hawm cov tshuaj tiv thaiv ntawm lub voj voog ornithine. Urea yog cov khoom tsim tawm ntawm cov tsiaj ureotelic, suav nrog tib neeg.
Urea yog ib txoj hauv kev kom tshem tawm cov nitrogen ntau dhau ntawm lub cev. Kev tsim cov tshuaj no muaj kev tiv thaiv kev ua haujlwm, vim. urea precursor - ammonia, tshuaj lom rau tib neeg lub hlwb.
Thaum ua 100 g ntawm cov protein ntau yam, 20-25 g ntawm urea raug tso tawm hauv cov zis. Cov tshuaj yog synthesized nyob rau hauv daim siab, thiab tom qab ntawd nrog cov ntshav khiav nkag mus rau hauv lub nephron ntawm lub raum thiab tawm nrog rau cov zis.
Lub siab yog lub hauv paus tseem ceeb rau kev sib txuas ntawm urea
Nyob hauv tib neeg lub cev tsis muaj lub xovtooj zoo li no uas muaj tag nrho cov enzymes ntawm lub voj voog ornithine. Tsuas yog rau hepatocytes, tau kawg. Kev ua haujlwm ntawm daim siab tsis yog tsuas yog txhawm rau tsim thiab rhuav tshem hemoglobin, tab sis kuj ua tiav txhua qhov kev cuam tshuam ntawm urea synthesis.
Nyob hauv qabCov lus piav qhia ntawm lub voj voog ornithine haum rau qhov tseeb tias nws yog tib txoj hauv kev tshem tawm nitrogen los ntawm lub cev. Yog hais tias nyob rau hauv kev xyaum cov synthesis los yog kev ua ntawm lub ntsiab enzymes yog inhibited, lub synthesis ntawm urea yuav tsum nres, thiab lub cev yuav tuag los ntawm ib tug tshaj ntawm ammonia nyob rau hauv cov ntshav.
Ornithine voj voog. Biochemistry ntawm cov tshuaj tiv thaiv
Lub voj voog urea synthesis tshwm sim hauv ntau theem. Cov tswv yim dav dav ntawm lub voj voog ornithine tau nthuav tawm hauv qab no (daim duab), yog li peb yuav txheeb xyuas txhua qhov kev tawm tsam sib cais. Thawj ob theem tshwm sim ncaj qha hauv mitochondria ntawm lub siab hlwb.
NH3 reacts nrog carbon dioxide siv ob ATP molecules. Raws li qhov tshwm sim ntawm qhov kev siv hluav taws xob no, carbamoyl phosphate yog tsim, uas muaj cov ntawv cog lus macroergic. Cov txheej txheem no yog catalyzed los ntawm enzyme carbamoyl phosphate synthetase.
Carbamoyl phosphate reacts nrog ornithine los ntawm enzyme ornithine carbamoyl transferase. Raws li qhov tshwm sim, daim ntawv cog lus siab zog raug rhuav tshem, thiab citrulline tsim vim nws lub zog.
theem thib peb thiab tom ntej no tshwm sim tsis nyob hauv mitochondria, tab sis nyob rau hauv cytoplasm ntawm hepatocytes.
Muaj cov tshuaj tiv thaiv ntawm citrulline thiab aspartate. Nrog rau kev noj ntawm 1 ATP molecule thiab nyob rau hauv qhov kev txiav txim ntawm enzyme arginine-succinate synthase, arginine-succinate yog tsim.
Arginino-succinate, ua ke nrog cov enzyme arginino-succin-lyase, zom rau arginine thiab fumarate.
Arginine nyob rau hauv muaj dej thiab nyob rau hauv qhov kev txiav txim ntawm arginase yog tawg mus rau ornithine (1 cov tshuaj tiv thaiv) thiab urea (cov khoom kawg). Lub voj voog ua tiav.
Lub zog ntawm urea synthesis voj voog
Lub voj voog ornithine yog cov txheej txheem siv hluav taws xob uas siv cov nyiaj macroergic ntawm adenosine triphosphate (ATP) molecules tau noj. Thaum tag nrho 5 qhov kev tshwm sim, 3 ADP molecules raug tsim nyob rau hauv tag nrho. Tsis tas li ntawd, lub zog yog siv rau kev thauj khoom ntawm mitochondria mus rau cytoplasm thiab rov ua dua. ATP tuaj qhov twg?
Fumarate, uas tau tsim nyob rau hauv plaub cov tshuaj tiv thaiv, tuaj yeem siv los ua cov substrate hauv lub voj voog tricarboxylic acid. Thaum lub sij hawm synthesis ntawm malate los ntawm fumarate, NADPH raug tso tawm, uas ua rau 3 ATP molecules.
Glutamate deamination cov tshuaj tiv thaiv kuj ua lub luag haujlwm hauv kev muab lub siab lub hlwb nrog lub zog. Tib lub sijhawm, 3 ATP molecules kuj raug tso tawm, uas yog siv rau kev sib txuas ntawm urea.
Txoj cai ntawm ornithine voj voog kev ua haujlwm
Nquag, cov cascade ntawm urea synthesis cov tshuaj tiv thaiv ua haujlwm ntawm 60% ntawm nws qhov ua tau. Nrog rau cov ntsiab lus protein ntau ntxiv hauv cov zaub mov, cov tshuaj tiv thaiv tau nrawm dua, uas ua rau muaj kev nce ntxiv hauv kev ua haujlwm tag nrho. Cov kab mob metabolic ntawm lub voj voog ornithine tau pom thaum lub cev ua haujlwm siab thiab yoo mov ntev, thaum lub cev pib zom nws cov proteins.
Cov kev cai ntawm lub voj voog ornithine tuaj yeem tshwm sim ntawm qib biochemical. Ntawm no lub hom phiaj yog lub ntsiab enzyme carbamoyl phosphate synthetase. Nws allosteric activator yog N-acetyl-glutamate. Nrog nws cov ntsiab lus siab hauv lub cev, urea synthesis tshwm sim ua haujlwm ib txwm. Nrog ib tug tsis muaj cov khoom nws tus kheej los yog nwsprecursors, glutamate thiab acetyl-CoA, lub voj voog ornithine poob nws cov haujlwm ua haujlwm.
Kev sib raug zoo ntawm lub voj voog urea synthesis thiab Krebs cycle
Cov kev cuam tshuam ntawm ob txheej txheem tshwm sim hauv mitochondrial matrix. Qhov no ua rau nws muaj peev xwm ua tau rau qee cov tshuaj organic los koom hauv ob txoj kev biochemical.
CO2 thiab adenosine triphosphate, uas yog tsim nyob rau hauv lub voj voog citric acid, yog precursors ntawm carbamoyl phosphate. ATP kuj yog qhov tseem ceeb tshaj plaws ntawm lub zog.
Lub voj voog ornithine, uas nws cov kev cuam tshuam tshwm sim hauv daim siab hepatocytes, yog qhov chaw ntawm fumarate, yog ib qho tseem ceeb tshaj plaws hauv lub voj voog Krebs. Ntxiv mus, cov tshuaj no, raws li ib tug tshwm sim ntawm ob peb kauj ruam cov tshuaj tiv thaiv, ua rau kom aspartate, uas, nyob rau hauv lem, yog siv nyob rau hauv lub biosynthesis ntawm lub ornithine voj voog. Fumarate cov tshuaj tiv thaiv yog ib qho ntawm NADP, uas tuaj yeem siv los ua phosphorylate ADP rau ATP.
Lub ntsiab lus ntawm lub voj voog ornithine
Feem ntau ntawm nitrogen nkag mus rau hauv lub cev ua ib feem ntawm cov proteins. Hauv cov txheej txheem ntawm cov metabolism, cov amino acids raug rhuav tshem, ammonia yog tsim los ua cov khoom kawg ntawm cov txheej txheem metabolic. Lub voj voog ornithine muaj ntau qhov kev sib txuas lus sib law liag, lub luag haujlwm tseem ceeb ntawm kev ua kom detoxify NH 3 los ntawm kev hloov mus rau hauv urea. Urea, dhau los, nkag mus rau nephron ntawm lub raum thiab tawm hauv lub cev nrog cov zis.
Ntxiv rau, los ntawm cov khoom lag luam ntawm lub voj voog ornithine yog qhov chaw ntawm arginine, ib qho ntawm cov amino acids tseem ceeb.
Kev ua txhaum hauv kev sib txuasurea tuaj yeem ua rau muaj kab mob xws li hyperammonemia. Cov kab mob no yog tus cwj pwm los ntawm kev nce siab ntawm ammonium ions NH4+ hauv tib neeg cov ntshav. Cov ions no cuam tshuam rau lub neej ntawm lub cev, tig tawm lossis ua kom qeeb qee cov txheej txheem tseem ceeb. Tsis quav ntsej tus kab mob no tuaj yeem ua rau tuag taus.
