Nyob rau xyoo 1972, txoj kev xav tau muab tso rau pem hauv ntej tias ib feem ntawm daim nyias nyias nyob ib puag ncig ntawm lub cell thiab ua ntau txoj haujlwm tseem ceeb, thiab cov qauv thiab kev ua haujlwm ntawm cov cell membranes yog cov teeb meem tseem ceeb txog kev ua haujlwm ntawm txhua lub hlwb hauv lub cev.. Cell txoj kev xav tau nthuav dav hauv lub xyoo pua 17th, nrog rau kev tsim kho lub tshuab tsom. Nws tau paub tias cov nroj tsuag thiab tsiaj cov ntaub so ntswg yog tsim los ntawm cov hlwb, tab sis vim tsis muaj kev daws teeb meem ntawm cov cuab yeej, nws tsis tuaj yeem pom muaj teeb meem nyob ib puag ncig cov tsiaj cell. Nyob rau hauv lub xyoo pua 20th, cov tshuaj lom neeg ntawm daim nyias nyias tau kawm kom ntxaws, nws tau pom tias lipids yog nws lub hauv paus.
qauv thiab kev ua haujlwm ntawm cell membranes
Cov cell membrane ncig lub cytoplasm ntawm cov hlwb nyob, lub cev sib cais cov khoom hauv lub cev los ntawm ib puag ncig sab nraud. Cov kab mob, cov kab mob, thiab cov nroj tsuag kuj muaj cov phab ntsa ntawm tes uas muab kev tiv thaiv thiab tiv thaiv kev hla ntawm cov molecules loj. Cell membranes kuj ua lub luag haujlwm hauvtsim ntawm cytoskeleton thiab txuas mus rau lub extracellular matrix ntawm lwm yam tseem ceeb hais. Qhov no yog qhov tsim nyog txhawm rau tuav lawv ua ke, tsim cov ntaub so ntswg thiab cov kabmob ntawm lub cev. Cov yam ntxwv ntawm cov cell membrane muaj xws li permeability. Lub luag haujlwm tseem ceeb yog kev tiv thaiv. Lub membrane muaj phospholipid txheej nrog embedded proteins. Qhov no yog koom nrog hauv cov txheej txheem xws li cell adhesion, ion conduction, thiab signaling systems thiab ua hauj lwm raws li ib tug txuas rau ob peb extracellular lug, nrog rau cov phab ntsa, glycocalyx, thiab sab hauv cytoskeleton. Daim nyias nyias kuj tuav lub peev xwm ntawm tes los ntawm kev ua raws li cov lim dej xaiv. Nws yog selectively permeable rau ions thiab organic molecules thiab tswj kev txav ntawm cov khoom.
Kev lom neeg cov txheej txheem cuam tshuam nrog cov cell membrane
1. Passive diffusion: Qee yam khoom (me me molecules, ions), xws li carbon dioxide (CO2) thiab oxygen (O2), tuaj yeem nthuav tawm los ntawm cov plasma membrane. Lub plhaub ua raws li kev txwv rau qee cov molecules thiab ions uas tuaj yeem ua kom pom tseeb ntawm ob sab.
2. Transmembrane channel thiab transporter protein: Cov khoom noj xws li qabzib lossis amino acids yuav tsum nkag mus rau hauv lub cell, thiab qee cov khoom lag luam metabolic yuav tsum tawm mus.
3. Endocytosis yog tus txheej txheem uas cov molecules raug coj mus. Ib me ntsis deformation (invagination) yog tsim nyob rau hauv lub plasma daim nyias nyias, nyob rau hauv uas cov khoom yuav tsum tau raug nqos. Nws xav taulub zog thiab yog li yog ib hom kev thauj mus los.
4. Exocytosis: tshwm sim nyob rau hauv ntau lub hlwb kom tshem tawm cov undigested residues ntawm cov khoom coj los ntawm endocytosis thiaj li tso cov tshuaj xws li cov tshuaj hormones thiab enzymes thiab thauj cov khoom tag nrho los ntawm cellular barrier.
qauv molecular
Cell membrane yog ib daim nyias nyias, muaj feem ntau ntawm phospholipids thiab cais cov ntsiab lus ntawm tag nrho cov cell los ntawm ib puag ncig sab nraud. Cov txheej txheem tsim tshwm sim spontaneously nyob rau hauv ib txwm muaj mob. Yuav kom nkag siab txog cov txheej txheem no thiab piav qhia meej txog cov qauv thiab kev ua haujlwm ntawm cov cell membranes, nrog rau cov khoom, nws yog ib qho tsim nyog yuav tsum tau soj ntsuam cov qauv ntawm phospholipid, uas yog cov yam ntxwv ntawm cov qauv polarization. Thaum phospholipids nyob rau hauv dej ib puag ncig ntawm lub cytoplasm ncav cuag ib qho tseem ceeb concentration, lawv muab ua ke rau hauv micelles, uas yog ruaj khov nyob rau hauv cov dej ib puag ncig.
Cov khoom muaj nuj nqis
- Kev ruaj ntseg. Qhov no txhais tau tias tom qab tsim ntawm daim nyias nyias yuav tsis zoo li tawg.
- Txoj kev. Cov lipid daim nyias nyias muaj kev ntseeg siab txaus los tiv thaiv kev hla ntawm cov khoom polar; ob qho tib si yaj tshuaj (ions, qabzib, amino acids) thiab ntau cov molecules loj (cov protein) tsis tuaj yeem hla dhau ntawm ciam teb.
- Dynamic cim. Qhov no yog kab tias cov cuab yeej tseem ceeb tshaj plaws thaum xav txog cov qauv ntawm tes. Lub cell membrane tuaj yeemyuav raug rau ntau yam deformations, tuaj yeem folded thiab khoov yam tsis muaj kev sib tsoo. Nyob rau hauv cov xwm txheej tshwj xeeb, xws li fusion ntawm vesicles lossis budding, nws tuaj yeem tawg, tab sis tsuas yog ib ntus xwb. Nyob rau hauv chav tsev kub, nws cov lipid muaj nyob rau hauv tas li, chaotic motion, tsim ib tug ruaj khov ciam teb.
Ua kua Mosaic Model
Hais txog cov qauv thiab kev ua haujlwm ntawm cov cell membranes, nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias hauv kev pom niaj hnub no, daim nyias nyias raws li cov qauv ua kua mosaic tau txiav txim siab xyoo 1972 los ntawm cov kws tshawb fawb Singer thiab Nicholson. Lawv txoj kev xav qhia txog peb yam tseem ceeb ntawm cov qauv membrane. Integral membrane proteins muab ib lub mosaic qauv rau daim nyias nyias, thiab lawv muaj peev xwm ntawm lateral nyob rau hauv lub dav hlau txav vim qhov txawv txav ntawm lipid lub koom haum. Transmembrane proteins kuj muaj peev xwm ua tau mobile. Ib qho tseem ceeb feature ntawm daim nyias nyias yog nws asymmetry. Tus qauv ntawm lub cell yog dab tsi? Cell membrane, nucleus, proteins thiab lwm yam. Lub cell yog lub hauv paus ntawm lub neej, thiab tag nrho cov kab mob yog tsim los ntawm ib los yog ntau lub hlwb, txhua tus muaj ib tug natural barrier cais nws los ntawm nws ib puag ncig. Qhov no sab nraud ciam teb ntawm lub cell tseem hu ua plasma membrane. Nws yog tsim los ntawm plaub hom molecules: phospholipids, cholesterol, proteins, thiab carbohydrates. Cov qauv ua kua mosaic piav qhia cov qauv ntawm cov cell membrane raws li hauv qab no: yoog raws thiab elastic, zoo ib yam li cov roj zaub, kom txhua yamtus neeg molecules tsuas yog ntab hauv cov kua nruab nrab, thiab lawv txhua tus muaj peev xwm txav mus rau sab hauv lub plhaub ntawd. Mosaic yog ib yam uas muaj ntau yam sib txawv. Hauv plasma membrane, nws yog sawv cev los ntawm phospholipids, cholesterol molecules, proteins thiab carbohydrates.
phospholipids
Phospholipids tsim cov qauv ntawm cov cell membrane. Cov molecules no muaj ob qhov kawg: lub taub hau thiab tus Tsov tus tw. Lub taub hau kawg muaj phosphate pawg thiab yog hydrophilic. Qhov no txhais tau hais tias nws yog attracted rau dej molecules. Tus Tsov tus tw yog tsim los ntawm hydrogen thiab carbon atoms hu ua fatty acid chains. Cov chains no yog hydrophobic, lawv tsis nyiam sib tov nrog dej molecules. Cov txheej txheem no zoo ib yam li qhov tshwm sim thaum koj ncuav roj zaub rau hauv dej, uas yog, nws tsis yaj hauv nws. Cov yam ntxwv ntawm cov cell membrane yog txuam nrog lub npe hu ua lipid bilayer, uas muaj phospholipids. Hydrophilic phosphate hau yeej ib txwm nyob qhov twg muaj dej nyob rau hauv daim ntawv ntawm intracellular thiab extracellular kua. Lub hydrophobic tails ntawm phospholipids nyob rau hauv daim nyias nyias yog tsim nyob rau hauv xws li ib txoj kev uas lawv kom lawv deb ntawm dej.
Thaum tib neeg hnov lo lus "cholesterol", tib neeg feem ntau xav tias nws phem. Txawm li cas los xij, cov roj (cholesterol) yog qhov tseem ceeb ntawm cov cell membranes. Nws cov molecules muaj plaub lub nplhaib ntawm hydrogen thiab carbon atoms. Lawv yog hydrophobic thiab tshwm sim ntawm hydrophobic tails nyob rau hauv lub lipid bilayer. Lawv qhov tseem ceeb nyob hauvtswj kev sib xws, lawv txhawb cov membranes, tiv thaiv crossover. Cov roj cholesterol molecules tseem ua rau cov phospholipid tails los ntawm kev sib cuag thiab tawv. Qhov no guarantees fluidity thiab yooj. Membrane proteins ua raws li cov enzymes kom ceev cov tshuaj tiv thaiv, ua raws li cov receptors rau cov molecules tshwj xeeb, los yog thauj cov khoom hla lub cell membrane.
Carbohydrates, los yog saccharides, tsuas yog pom nyob rau sab extracellular ntawm cell membrane. Ua ke lawv tsim glycocalyx. Nws muab cushioning thiab tiv thaiv cov plasma membrane. Raws li cov qauv thiab hom carbohydrates hauv glycocalyx, lub cev tuaj yeem paub cov hlwb thiab txiav txim siab seb lawv yuav tsum nyob ntawd lossis tsis.
Cov qauv ntawm cov cell membrane ntawm cov tsiaj cell tsis tuaj yeem xav txog yam tsis muaj qhov tseem ceeb xws li cov protein. Txawm li cas los xij, lawv tuaj yeem ua rau qis dua qhov loj rau lwm qhov tseem ceeb - lipids. Muaj peb lub ntsiab membrane proteins.
- Integral. Lawv tag nrho npog ob txheej, cytoplasm thiab extracellular ib puag ncig. Lawv ua lub luag haujlwm thauj thiab teeb liab.
- Pib. Proteins txuas rau daim nyias nyias los ntawm electrostatic los yog hydrogen bonds ntawm lawv cytoplasmic los yog extracellular nto. Lawv koom nrog feem ntau yog ib txoj hauv kev txuas rau cov protein ntau.
- Transmembrane. Lawv ua haujlwm enzymatic thiab signaling, thiab kuj hloov cov qauv ntawm cov lipid ob txheej ntawm daim nyias nyias.
Kev ua haujlwm ntawm cov kab mob lom neeg
Cov nyhuv hydrophobic, uas tswj tus cwj pwm ntawm hydrocarbons hauv dej, tswj cov qauv tsim los ntawm daim nyias nyias lipids thiab membrane proteins. Ntau yam khoom ntawm daim nyias nyias tau pom zoo los ntawm cov nqa ntawm lipid bilayers, uas tsim cov qauv yooj yim rau txhua daim nyias nyias. Integral membrane proteins yog ib feem zais nyob rau hauv lub lipid bilayer. Transmembrane proteins muaj lub koom haum tshwj xeeb ntawm cov amino acids nyob rau hauv lawv cov thawj theem.
Peripheral membrane proteins zoo ib yam li cov soluble, tab sis lawv kuj yog daim nyias nyias. Cov cell membrane tshwj xeeb muaj cov haujlwm tshwj xeeb ntawm tes. Cov qauv thiab kev ua haujlwm ntawm cov cell membranes cuam tshuam rau lub cev li cas? Kev ua haujlwm ntawm tag nrho cov kab mob nyob ntawm seb cov txheej txheem lom neeg li cas. Los ntawm intracellular organelles, extracellular thiab intercellular kev sib tshuam ntawm daim nyias nyias, cov qauv tsim nyog rau lub koom haum thiab kev ua tau zoo ntawm kev ua haujlwm lom neeg raug tsim. Ntau yam qauv thiab kev ua haujlwm zoo ib yam rau cov kab mob, cov hlwb eukaryotic, thiab cov kab mob hauv lub hnab. Tag nrho cov kab mob lom yog tsim los ntawm cov lipid bilayer, uas txiav txim siab muaj ntau tus yam ntxwv. Membrane proteins muaj ntau yam haujlwm tshwj xeeb.
- Control. Plasma daim nyias nyias ntawm cov hlwb txhais cov ciam teb ntawm kev sib cuam tshuam ntawm tes nrog ib puag ncig.
- Tsheb thauj mus los. Lub intracellular daim nyias nyias ntawm cov hlwb tau muab faib ua ob peb qhov kev ua haujlwm nrog sib txawvInternal muaj pes tsawg leeg, txhua yam uas tau txais kev txhawb nqa los ntawm kev thauj khoom tsim nyog ua ke nrog kev tswj xyuas permeability.
- Signal transduction. Membrane fusion muab cov txheej txheem rau kev ceeb toom ntawm intracellular vesicular thiab tiv thaiv ntau yam kab mob los ntawm kev nkag mus rau hauv cell.
Lub ntsiab lus thiab xaus
Cov qauv ntawm cov cell sab nrauv cuam tshuam rau tag nrho lub cev. Nws ua lub luag haujlwm tseem ceeb hauv kev tiv thaiv kev ncaj ncees los ntawm kev tso cai tsuas yog xaiv cov tshuaj nkag mus. Nws kuj tseem yog lub hauv paus zoo rau kev txhim kho cytoskeleton thiab cell phab ntsa, uas pab tswj cov duab ntawm tes. Lipids tsim txog li 50% ntawm daim nyias nyias ntawm cov cell feem ntau, txawm hais tias qhov no txawv nyob ntawm seb hom membrane. Cov qauv ntawm cov ntaub so ntswg sab nrauv ntawm cov tsiaj nyeg yog complex, nws muaj plaub lub ntsiab phospholipids. Ib qho tseem ceeb ntawm cov lipid bilayers yog tias lawv coj zoo li cov kua dej ob sab hauv uas cov molecules ib leeg tuaj yeem tig thiab txav mus tom qab. Xws li fluidity yog ib qho cuab yeej tseem ceeb ntawm daim nyias nyias, uas yog txiav txim siab nyob ntawm qhov kub thiab txias lipid muaj pes tsawg leeg. Vim yog lub nplhaib hydrocarbon, cov roj cholesterol plays lub luag haujlwm hauv kev txiav txim siab fluidity ntawm daim nyias nyias. Kev xaiv permeability ntawm cov kab mob lom rau cov molecules me tso cai rau lub cell los tswj thiab tswj nws cov qauv sab hauv.
Xav txog cov qauv ntawm tes (cell membrane, nucleus, thiab lwm yam), peb tuaj yeem xaus tiashais tias lub cev yog ib qho kev tswj hwm tus kheej uas tsis tuaj yeem ua phem rau nws tus kheej yam tsis muaj kev pab sab nraud thiab yuav nrhiav txoj hauv kev los kho, tiv thaiv thiab ua haujlwm zoo rau txhua lub cell.
