Mechanism ntawm Kev Thauj Khoom Oxygen los ntawm Hemoglobin
Cov pa oxygen yog lub "roj" tseem ceeb rau cov cell kom tsim tau lub zog los ntawm kev ua pa ntawm cov cell. Txawm li cas los xij, cov pa oxygen tsis tuaj yeem thauj mus rau hauv ntau qhov tsuas yog los ntawm kev yaj hauv cov ntshav plasma. Cov pa oxygen solubility hauv plasma yog qhov tsawg heev, xav tau lub kaw lus thauj mus los zoo dua. Qhov no yog qhov uas hemoglobin - cov protein tseem ceeb hauv cov qe ntshav liab - ua lub luag haujlwm tseem ceeb. Hemoglobin ua rau cov pa oxygen nqus tau hauv lub ntsws, thauj mus los ntawm cov hlab ntsha, thiab tso tawm hauv cov nqaij raws li qhov xav tau. Tsab xov xwm no tham txog cov txheej txheem ntawm kev thauj oxygen los ntawm hemoglobin, suav nrog nws cov qauv, cov txheej txheem ntawm kev khi thiab tso tawm oxygen, thiab cov yam ntxwv uas cuam tshuam rau hemoglobin affinity.
Cov Qauv Hemoglobin thiab Vim Li Cas Nws Tseem Ceeb
Hemoglobin (Hb) yog ib hom protein uas muaj nyob hauv cov qe ntshav liab (erythrocytes). Hauv cov neeg laus, hom uas pom ntau tshaj plaws yog hemoglobin A (HbA), uas muaj plaub txoj saw hlau globin: ob txoj saw hlau alpha (α) thiab ob txoj saw hlau beta (β). Txhua txoj saw hlau globin nqa ib pawg heme, yog li ntawd ib lub hemoglobin molecule muaj tag nrho plaub txoj saw hlau heme.
Pawg heme muaj ib lub hlau atom (Fe²⁺) nyob hauv nruab nrab. Cov hlau no khi ncaj qha rau cov pa oxygen (O₂). Vim tias muaj plaub lub hemes, ib lub hemoglobin molecule tuaj yeem khi txog plaub lub oxygen molecule. Lub qauv tetrameric ntawm hemoglobin tsis yog tsuas yog "lub thawv" rau cov pa oxygen, tab sis kuj yog qhov tseem ceeb rau nws cov khoom sib koom tes: kev khi ntawm oxygen rau ib lub heme cuam tshuam rau qhov yooj yim uas oxygen khi rau lwm lub hemes.
Cov qauv ntawm hemoglobin tuaj yeem hloov pauv raws li qhov xwm txheej. Hais yooj yim xwb, muaj ob lub xeev tseem ceeb: lub xeev T (tense), uas muaj qhov sib txuas tsawg dua rau oxygen, thiab lub xeev R (so), uas muaj qhov sib txuas ntau dua. Kev hloov pauv T mus rau R yog lub hauv paus rau kev khi oxygen zoo hauv lub ntsws thiab kev tso tawm zoo hauv cov ntaub so ntswg.
Kev Sib Txuas Lus ntawm Oxygen hauv Lub Ntsws
Hauv cov ntsws, tshwj xeeb tshaj yog nyob rau hauv cov hlab ntsha alveolar, qhov siab ib nrab ntawm cov pa oxygen (pO₂) siab heev. Cov pa oxygen kis los ntawm cov hlab ntsha alveoli mus rau hauv cov ntshav vim yog qhov siab hloov pauv. Thaum nws nkag mus rau hauv cov ntshav liab, cov pa oxygen rov qab khi rau cov hlau (Fe²⁺) hauv cov heme los tsim cov oxyhemoglobin (HbO₂).
Qhov kev khi no tsis yog ib qho txheej txheem yooj yim "on-off". Thaum ib lub O₂ molecule khi, hemoglobin yuav hloov pauv qhov sib txawv uas ua rau nws muaj feem cuam tshuam rau qhov chaw tom ntej. Qhov no yog qhov tshwm sim ntawm kev koom tes zoo. Yog li ntawd, kev sib raug zoo ntawm hemoglobin saturation thiab pO₂ yog sigmoidal (ib qho S-puab), es tsis yog ib txoj kab ncaj. Cov duab sigmoidal no ua rau hemoglobin ua haujlwm tau zoo heev: nws yooj yim "them" ntawm pO₂ siab (lub ntsws) thiab yooj yim "tso tawm" nws cov nqi ntawm pO₂ qis dua (cov ntaub so ntswg).
Nyob rau hauv cov xwm txheej ib txwm muaj, ntawm alveolar pO₂ ntawm kwv yees li 100 mmHg, hemoglobin saturation yuav luag 97–99%. Qhov no txhais tau tias feem ntau ntawm cov chaw khi rau hemoglobin yog nyob los ntawm oxygen. Qhov no yog qhov tseem ceeb kom ntseeg tau tias muaj peev xwm nqa oxygen ntau tshaj plaws thaum lub sijhawm ua ub no.
Kev Thauj Khoom Pa oxygen hauv Kev Ncig Tebchaws
Tom qab cov qe ntshav liab tawm hauv lub ntsws, cov ntshav ntawm cov hlab ntsha nqa cov pa oxygen thoob plaws lub cev. Cov pa oxygen hauv cov ntshav muaj ob hom: khi rau hemoglobin (feem ntau) thiab yaj hauv cov ntshav (tsawg heev). Lub cev, cov pa oxygen uas yaj tseem ceeb vim nws txiav txim siab pO₂ thiab txhawb kev sib kis ntawm cov pa oxygen los ntawm cov ntshav mus rau cov nqaij. Txawm li cas los xij, yog tsis muaj hemoglobin, tag nrho cov pa oxygen hauv cov ntshav yuav poob qis heev, vim tias cov ntshav yuav tsis muaj peev xwm yaj cov pa oxygen txaus.
Hemoglobin ua haujlwm zoo li lub "buffer" oxygen. Nws nqus oxygen thaum nws muaj ntau thiab tso nws tawm thaum cov nqaij xav tau. Lub tshuab no tswj tau qhov muaj oxygen txaus txawm tias cov nqaij xav tau hloov pauv.
Kev Tso Pa oxygen Hauv Cov Nqaij
Hauv cov nqaij ntshiv peripheral, pO₂ qis dua li hauv cov ntsws vim tias cov cell siv oxygen tas li los tsim ATP. Cov pa oxygen kis los ntawm cov hlab ntsha mus rau hauv cov kua dej interstitial thiab tom qab ntawd mus rau hauv cov cell. Thaum cov pa oxygen yaj txo qis, hemoglobin teb los ntawm kev tso cov pa oxygen khi kom tswj tau qhov sib npaug.
Kev tso pa oxygen yog cuam tshuam los ntawm lub xeev metabolic ntawm cov ntaub so ntswg. Cov ntaub so ntswg nquag (piv txwv li, cov leeg nqaij thaum lub sijhawm tawm dag zog) tsim ntau CO₂, ntau hydrogen ions (txo pH), thiab cua sov, tag nrho cov no txhawb kom hemoglobin tso pa oxygen yooj yim dua. Qhov no ua kom ntseeg tau tias oxygen muaj nyob rau qhov chaw uas nws xav tau tshaj plaws.
Thaum cov nqaij nruab nrab pO₂ ntawm kwv yees li 40 mmHg, hemoglobin saturation poob qis mus txog li 75%. Qhov no txhais tau tias kwv yees li 25% ntawm cov pa oxygen "tawm mus" rau cov nqaij thaum so. Thaum cov dej num nce ntxiv, cov nqaij pO₂ tuaj yeem poob qis dua, ua rau hemoglobin tso tawm ntau cov pa oxygen.
Bohr Effect: Lub Luag Haujlwm ntawm CO₂ thiab pH
Ib qho ntawm cov txheej txheem tseem ceeb tshaj plaws hauv kev tswj hwm kev tso pa oxygen yog Bohr effect. Bohr effect piav qhia tias kev nce CO₂ thiab txo qis pH (ntau acidic) txo qis hemoglobin qhov kev sib raug zoo rau oxygen, hloov qhov nkhaus oxygen dissociation mus rau sab xis. Hauv lwm lo lus, ntawm tib pO₂, hemoglobin yuav nqa tsawg dua oxygen thiab tso ntau dua rau cov ntaub so ntswg.
Hauv kev tshuaj lom neeg, CO₂ tuaj yeem ua rau dej sib xyaw ua ke los ua cov pa roj carbonic acid, uas tom qab ntawd tawg ua H⁺ thiab bicarbonate (HCO₃⁻). H⁺ yuav khi rau qee qhov ntawm hemoglobin, ua kom nws lub xeev T tsis muaj zog. Tsis tas li ntawd, qee cov CO₂ tuaj yeem khi ncaj qha rau hemoglobin los ua carbaminohemoglobin, uas kuj txhawb nqa kev tso pa oxygen. Yog li, cov ntaub so ntswg uas tsim ntau CO₂ yuav "thov" ntau cov pa oxygen los ntawm kev hloov pauv hauv cov ntshav ib puag ncig.
Hauv cov ntsws, qhov xwm txheej rov qab los: CO₂ raug ntiab tawm, pH nce siab, thiab hemoglobin rov qab tau nws qhov kev sib raug zoo rau oxygen, ua rau nws yooj yim khi.
Cov Nyhuv ntawm Kub thiab Kev Ua Haujlwm Metabolic
Qhov kub kuj cuam tshuam rau hemoglobin affinity. Qhov kub ntxiv—zoo li cov leeg ua haujlwm—feem ntau hloov qhov nkhaus dissociation mus rau sab xis, ua rau nws yooj yim dua rau hemoglobin tso pa oxygen. Ntawm qhov tod tes, thaum qhov kub qis dua, hemoglobin feem ntau tuav oxygen nruj dua. Qhov no pab txhawb rau kev faib pa oxygen ntau dua rau cov nqaij ua haujlwm, sov.
Lub Luag Haujlwm ntawm 2,3-BPG hauv Kev Hloov Kho
Cov qe ntshav liab muaj ib qho tseem ceeb hu ua 2,3-bisphosphoglycerate (2,3-BPG), uas yog ib yam khoom ntawm glycolysis. 2,3-BPG khi rau deoxygenated (oxygen-depleted) hemoglobin thiab ua kom nws lub xeev T ruaj khov, yog li ntawd nws txo qis nws qhov kev sib raug zoo rau oxygen. Yog li ntawd, oxygen raug tso tawm yooj yim dua rau hauv cov nqaij.
Cov theem 2,3-BPG tuaj yeem nce ntxiv rau qee yam mob, xws li nyob rau qhov chaw siab, ntshav tsis txaus, lossis hypoxia ntev. Kev nce 2,3-BPG pab lub cev hloov kho los ntawm kev txhawb nqa kev tso pa oxygen ntau dua hauv cov nqaij txawm tias pO₂ ib puag ncig qis dua.
Cov Kab Ntsig Kev Sib Cais Oxygen: Lub Hauv Paus ntawm Kev Nkag Siab Txog Hb Mechanism
Daim kab nkhaus oxygen-hemoglobin dissociation qhia txog kev sib raug zoo ntawm pO₂ thiab hemoglobin saturation. Daim duab sigmoid qhia txog kev koom tes. Qhov "tiaj" ntawm pO₂ siab pab tswj kom muaj kev saturation siab hauv lub ntsws txawm tias thaum pO₂ poob me ntsis. Qhov "nqaim" ntawm pO₂ nruab nrab-qis ua rau cov pa oxygen tso tawm teb tau zoo heev hauv cov nqaij: qhov txo qis me ntsis hauv pO₂ tuaj yeem ua rau muaj cov pa oxygen tso tawm ntau dua.
Kev hloov ntawm qhov nkhaus mus rau sab xis qhia txog kev txo qis ntawm kev sib raug zoo (muaj ntau cov pa oxygen raug tso tawm), ua rau muaj CO₂ ntau ntxiv, pH txo qis, kub nce ntxiv, thiab 2,3-BPG ntau ntxiv. Kev hloov mus rau sab laug qhia txog kev nce ntxiv ntawm kev sib raug zoo (cov pa oxygen tsis yooj yim tso tawm), piv txwv li nyob rau hauv cov xwm txheej ntawm CO₂ qis, pH siab, kub qis, lossis qee hom hemoglobin.
Xaus
Lub tshuab ntawm kev thauj cov pa oxygen los ntawm hemoglobin yog qhov tshwm sim ntawm kev tsim qauv zoo heev. Hemoglobin koom tes khi cov pa oxygen hauv lub ntsws, thauj nws los ntawm kev ncig, thiab tom qab ntawd tso nws mus rau cov ntaub so ntswg raws li qhov xav tau rau kev tswj hwm metabolic. Hemoglobin qhov kev nkag siab rau pH, CO₂, kub, thiab 2,3-BPG ua rau kev faib cov pa oxygen hloov pauv: cov ntaub so ntswg ntau dua tau txais cov pa oxygen ntau dua. Kev nkag siab txog lub tshuab no pab piav qhia ntau yam kev mob thiab kev ua haujlwm ntawm lub cev, los ntawm lub cev teb rau kev tawm dag zog mus rau kev hloov pauv ntawm qhov siab thiab kev thauj cov pa oxygen tsis zoo hauv ntau yam kab mob.
