ChapterChapter3MembraneTheLipidMembraneFigure.EssentialCellBiology(?GarlandScienceAbriefhistoryofplasmamembraneE.Oveiton,LipidNatureofE.GorterandF.Grendel,LipidH.Daveson,SandwichJ.Daniclli,PMalsocontainJ.D.Robertson,TEM,UnitS.J.SingerandG.L.Nicolson,FluidmosaicFigure.AcellmembranecanbeviewedinanumberofAAcellmembranehumanbloodcellincrosstwo- Fluidmosaic(twokeyFigure.EssentialCellBiology(?GarlandScienceLipidRaft(Simon,Raftsareenrichedwithcholesterolandgalactosylceramide(GalCer半乳糖神經(jīng)酰胺or半乳糖腦苷脂galactocerebrosideandstuddedwithproteins.Nature387:569-LipidRaftsmodel;FunctionalraftsincellmembranesFigure Lipid alkalinephosphatase堿性磷酸L-α-二油酸磷脂酰

Lipid3.13.1TheLipidThemainfunctionofcellTheplasmamembraneactasselective質(zhì)質(zhì)內(nèi)biomembrane=plasmamembrane+internalFigure.EssentialCellBiology(?GarlandScienceTheplasmamembraneisinvolvedincellcommunication,importandexportofmolecules,andcellgrowthandmotilityCellandFigure.EssentialCellBiology(?GarlandScienceLocalizationandorganizationoforFigure.EssentialCellBiology(?GarlandScienceThebasiccompositionsofsomebio-MembranelipidformbilayersinPhosphatidylcholine(磷脂酰膽堿isthemostphospholipidcell Figure.EssentialCellBiology(?GarlandScienceFigure.MolecularBiologyoftheCell(?GarlandScienceFourmajorphospholipidsinmammalianplasma Figure.MolecularBiologyoftheCell(?GarlandScience

鞘氨醇 Differenttypesofmembranelipidsareallamphipathic(兩親的Figure.EssentialCellBiology(?GarlandScienceAhydrophilic親水的moleculeacetoneattractswatermoleculesrequiresAhydrophobic疏水的molecule2-methylpropane(2-甲基丙烷tendstoavoidwatermolecules.Figure.EssentialCellBiology(?GarlandScienceFatmoleculesarehydrophobicwhereasphospholipidsareamphipathic兩親的Theenergycostisminimized,however,ifthehydrophobicmoleculesclustertogether,limitingtheircontactwithwatertothesmallestpossiblenumberofwatermolecules. Figure.EssentialCellBiology(?GarlandScienceAmphipathicphospholipidsformabilayerinFigure.EssentialCellBiology(?GarlandSciencePackingarrangementsofmoleculesinan微微雙分Lipidmoleculesspontaneouslyformoneorotherstructureinwater,dependingontheirFigure.MolecularBiologyoftheCell(?GarlandSciencespontaneouslycloseinonthemselvestoformsealedFigure.EssentialCellBiology(?GarlandScienceCrawlingAmicroscopicviewofspermduringinvitrofertilizationPhospholipidinsolventTheareaddedPhospholipidinsolventTheareaddedtoaddedtosolventflatlipidFigure.EssentialCellBiology(?GarlandScienceLiposomeforLiposomeforDrugFigure.Liposome(1999)byKosiThemobilityofphospholipidmoleculesinanartificiallipidbilayerMembraneMembranefluidisduetolipidfluidFigure.MolecularBiologyoftheCell(?GarlandScienceThefluidityofthebilayerisstrictlyconfinedoneneedneedFigure.MolecularBiologyoftheCell(?GarlandScienceThefluidityofalipidbilayerdependsonitsJusthowfluidalipidbilayerisatagiventemperaturedependsonitsphospholipidcompositionand,inparticular,onthenatureofthehydrocarbontails:thecloserandmoreregular themoreviscous粘性andlessfluidtwomajorpropertiesoftails: numberofdoubleunsaturatedhydrocarbon-----morefluidsaturatedhydrocarbon----moresolidThestructureofCholesterolinaInanimalcells,membranefluidityismodulatedbytheinclusionofthesterolcholesterol.Cholesteroltendstostiffencellmembranes.Figure.MolecularBiologyoftheCell(?GarlandScienceCholesteroltendstostiffencellFigure.EssentialCellBiology(?GarlandScienceFigure.MolecularBiologyoftheCell(?GarlandScienceEvidencesofmembranecellFigure.MolecularBiologyoftheCell(?GarlandScienceFluorescenceRecoveryAfterPhotobleachingFRAPdenotesanopticaltechniquecapablefyingthetwodimensionallateraldiffusionofamolecularlythinfilmcontainingfluorescentlylabeledprobes,ortoexaminesinglecells.Thistechniqueisveryusefulinbiologicalstudiesofcellmembranediffusionandproteinbinding.Inaddition,surfacedepositionofafluorescingphospholipidbilayer(ormonolayer)allowsthecharacterizationofhydrophobicsurfacesintermsofsurfacestructureandfreeenergy.Figure.EssentialCellBiology(?GarlandScience

Disadvantages:itisimpossibletowhatindividualmoleculesare FluorescencelossinphotobleachingFLIP,isatechniqueinfluorescencemicroscopywhichcanbeusedtoexaminethemovementordiffusionofmoleculesinsidecellsormembranes.Typicallyacellmembraneislabelledwithafluorescentdye,andaspecificareaofthelabeledmembraneisbleachedusingthebeamfromaconfocallaserscanningmicroscope.Thefluorescenceintensityfromthatregionofthemembraneismeasuredovertime.Motionoffluorescentmoleculesintoandalongthemembraneslowlyrestoresthefluorescenceinthebleachedregion,whiledepletingthefluorescenceinotherregions(byexchangeofbleachedforunbleachedFLIPFLIPFigure.MolecularBiologyoftheCell(?GarlandScienceProteinsshowdifferentpatternsofmotion

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Corralledwithinasmall byotherFigure.EssentialCellBiology(?GarlandScienceTherolesofthefluidityofalipidItenablesmembraneproteintodiffuserapidlyintheplaneofthebilayerandtointeractoneanother.e.g.cellsignaling.Itpermitsmembranelipidsandproteinstodiffusefromsitewheretheyareinsertedintothebilayeraftertheirsynthesistootherregionsofthecell.Itallowsmembranestofusewithoneanotherandmixtheirmolecules.Itensuresthatmembranemoleculesaredistributedevenlybetweendaughtercellswhenacelldivides.Thelipidbilayeristhelipidbilayercompositionisty:twosideare

Figure.EssentialCellBiology(?GarlandScienceGlycolipid糖脂半乳糖腦苷 Figure.MolecularBiologyoftheCell(?GarlandScience

Figure. ThelipidasymmetryisestablishedandmaintainedasthemembranegrowsIneucaryoticcells,newphospholipidsaremanufacturedbyenzymefacesthecytosol.Figure.EssentialCellBiology(?GarlandScienceMembraneassemblybeginsintheCertainphospholipidsareconfinedtosideofLightLightgreen:PSYellow:PERed:PCBrown:SM磷脂拼接 翻轉(zhuǎn)Figure.EssentialCellBiology(?GarlandScience

NewlysynthesizedphospholipidsareaddedtothecytosolicsideoftheERmembraneandthenredistributedbyenzymesthattransferthemfromonehalfofthelipidbilayertotheother.Theresultingcurvatureofthemembranemayactuallyhelpdrivesubsequentvesiclebudding.MembranesretaintheirorientationduringtransferbetweencellcompartmentsProteinattachedsugarfacingthenoncytosolicsideFigure.EssentialCellBiology(?GarlandScienceLipidasymmetryis duringmembranecytosolicsurfacenoncytosolicsurfaceMembranesretaintheirorientationevenaftertransferbetweencellFigure.MolecularBiologyoftheCell(?GarlandScienceEvidencesofmembraneFreezefracture:atechniqueforindicatingcellmembraneFigure. TheasymmetryoflipidisfunctionallyLightLightgreen:PSYellow:PERed:PCBrown:SMCombinewithLysorArgofglycophorinFigure.MolecularBiologyoftheCell(?GarlandScience聚糖，在細(xì)胞質(zhì)表面附著于收縮性蛋白(紅細(xì)胞膜內(nèi)蛋白和肌動(dòng)蛋白Convertingextracellularsignalsinto磷酸肌醇3激Figure.MolecularBiologyoftheCell(?GarlandScience3.2MembraneInanimal,proteinsconstituteabout50%of3.2MembranePlasmamembraneproteinshaveavarietyofFigure.EssentialCellBiology(?GarlandScienceFigure.EssentialCellBiology(?GarlandScienceMembraneproteinsassociatewiththelipidbilayerinvariouswaysA,B,C—Suchproteinsareknownasintegralmembraneproteins膜內(nèi)在蛋白Theremainingmembraneproteinsareknowsasperipheralmembraneproteins膜周邊蛋白.Figure.EssentialCellBiology(?GarlandScienceApolypeptidechainusuallycrossesthebilayerasanα-helixFigure.EssentialCellBiology(?GarlandScienceThepolypeptidechainofsometransmembranecrossesalipidbilayerasaβsheetthatiscurvedintoacylinder,formingan-endedkeg-likestructurecalledaβbarrel.Themoststrikingexampleofaβbarrelstructureisfoundintheporinprotein孔蛋白,whichformlarge,waterfilledporesinmitochondrialandbacterialmembranes.Figure.EssentialCellBiology(?GarlandScienceAsegmentofachaincrossingthelipidbilayerasanα-helixFigure.MolecularBiologyoftheCell(?GarlandScienceMembraneproteinatta entbyafattyacidchainoraprenyl含異戊二烯基的group Figure.MolecularBiologyoftheCell(?GarlandScienceConvertingasingle-chainmultipassproteinintoatwo-chainmultipassproteinFigure.MolecularBiologyoftheCell(?GarlandScienceStepsinthefoldingofamultipasstransemembraneFigure.MolecularBiologyoftheCell(?GarlandScienceMembraneproteinscanbesolubilizedindetergentsandpurifiedTwocommonlyuseddetergentsIthasanoninoizedbutpolarstructureatitshydrophilicend.Figure.EssentialCellBiology(?GarlandScienceMembraneproteinscanbesolubilizedbyamildFigure.EssentialCellBiology(?GarlandScienceTheuseofmildnonionicdetergentsforsolubilizing,purifying,andreconsitutingfunctionalmembraneproteinThemembraneproteinsdiffusemorefreelyandrapidlyinartificiallipidbilayersthanincellFigure.EssentialCellBiology(?GarlandScienceThecompletestructureisknownforrelativelyfewmembraneproteinsBacteriorhodopsin細(xì)菌視紫紅質(zhì)(或細(xì)菌紫膜質(zhì),嗜鹽性細(xì)菌鹽生鹽桿菌的紫膜中存在的色素蛋白)andaphotosyntheticreactioncenter—membraneproteinsthathaveimportantrolesinthecaptureanduseofenergyfromsunlight.Bacteriorhodopsinisasmallprotein(250AA)foundinlargeamountsintheplasmamembraneofanarchaean,calledHalobacteriumhalobium鹽生鹽桿菌.Bacteriorhodopsinisatypeoftransporterprotein,aclassoftransmembraneproteinsthatmovemoleculesandironandoutofcells.Figure.EssentialCellBiology(?GarlandScienceBacteriorhodopsin細(xì)菌視紫紅質(zhì)actsasaportongetsitsenergydirectlyfromEachBacteriorhodopsinmoleculecontainsasinglelightabsorbingnonprotein-calledretinal視黃醛--thatgivestheproteinandthebacteriumadeeppurpleFigure.EssentialCellBiology(?GarlandScienceThephotosyntheticreactionChlorophyllRhodopseudomonasFigure.EssentialCellBiology(?GarlandScienceTheplasmamembraneisreinforcedbythecellcortex細(xì)胞皮層RedbloodcellsaresmallandhaveadistinctiveflattenedshapeThemaincomponentoftheircortexistheproteinspectrin血影蛋白along,thin,flexiblerodabout100nminlength.Itwithactinformsameshworkthatprovidessupportfortheplasmamembraneandmaintainsthecell’sshape.Figure.EssentialCellBiology(?GarlandScienceAspectrinmeshworkformsthecellcortexinhumanredbloodWhatWhatcanyousayaboutthetarnsmembraneproteinmobilityinthemembrane?Figure.EssentialCellBiology(?GarlandScienceCellscanrestrictthemovementofmembraneFormationofmouse-humanhybridcellsshowsthatplasmamembraneproteinscanmovelaterallyinthelipidbilayerFigure.EssentialCellBiology(?GarlandSciencePlasmamembraneproteintolocalizedareaswithinthebilayer,therebycreatingfunctionallyspecializesregions,ormembrane s,onthecellororganellesurface.extracellarcelldiffusionbarriers(tightjunction)proteinonanotherFigure.EssentialCellBiology(?GarlandScienceAmembraneproteinisrestrictedtoaoftheplasmamembraneofanepithelialcellintheFigure.EssentialCellBiology(?GarlandScienceIsamembranewithmanyanchoredIsamembranewithmanyanchoredproteinsstillfluid?ThecellsurfaceiscoatedwithManymembraneproteininanimalcellsaregly