膜结构及其转运功能课件

厦门大学医学院戚智1Sizeofthecells2CellDiversity34一.细胞膜的分子结构质膜成分(CompositionofPlasmamembrane)脂类(Lipid)蛋白质(Protein)少量糖类(Carbohydrate)

5如何用最简单的办法证明细胞膜是单分子层、双分子层还是多分子层结构？如果把磷脂分子平铺在水面，其分子将如何分布？6FLUID-becauseindividualphospholipidsandproteinscanmoveside-to-sidewithinthelayer,likeit’saliquid.MOSAIC-becauseofthepatternproducedbythescatteredproteinmoleculeswhenthemembraneisviewedfromabove.FLUIDMOSAICMODEL(液态镶嵌模型)Thickness~6nmSinger&Nicholson,19727磷脂

Phospholipids

Hydrophilic:

“waterloving”Hydrophobic:“waterfearing”（一）细胞膜的脂质脂质分子种类:磷脂(Phospholipid)：>70%胆固醇(Cholesterol)：<30%糖脂：<10%

鞘脂(Sphingolipids

):少量.双嗜性分子（Amphipathicmolecule）胆固醇8（二）细胞膜的蛋白

MembraneProteinsProteinsdeterminemembrane’sspecificfunctions:Plasmamembrane&organellemembraneseachhaveuniquecollectionsofproteinsMembraneproteins:peripheralproteins(表面蛋白):resideoutsidehydrophobicregionoflipids,looselyboundtosurfaceofmembraneintegralproteins

（整合蛋白）:embeddedwithinbilayer,usuallyacrosswholemembranetransportproteinschannels,permeases(pumps)9（三）细胞膜的糖类

MembranecarbohydratesPlayakeyroleincell-cellrecognitionabilityofacelltodistinguishonecellfromanotherantigensimportantinorgan&

tissuedevelopmentbasisforrejectionof

foreigncellsby

immunesystemGlycoprotein糖蛋白Glycolipid糖脂10MembraneStructure:ProteintoLipidRatiovariesfromcelltypetocelltypeRatioforcellswithhighmetabolicactivity功能活跃的细胞，其膜蛋白含量较高

52%40%11二、跨细胞膜的物质转运（一）单纯扩散Simplediffusion（二）易化扩散（Facilitateddiffusion）1.经通道易化扩散（Facilitateddiffusionviaionchannel）2.经载体的易化扩散（Facilitateddiffusionviacarrier）(三)主动转运（Activetransport）(2）原发性主动转运；Primaryactivetransport(3)继发性主动转运；Secondaryactivetransport12（一）单纯扩散

SimpleDiffusion-RequiresNOenergyDiffusionisthenetmovementofmolecules(orions)fromaregionoftheirhighconcentrationtoaregionoftheirlowerconcentration.

Themoleculesmovedownaconcentrationgradient.

Moleculeshavekineticenergy,whichmakesthemmoveaboutrandomly.

Asaresultofdiffusionmoleculesreachanequilibriumwheretheyareevenlyspreadout.Thisiswhenthereisnonetmovementofmoleculesfromeitherside.13141516①Highspeed;(106~108/sec)②Selectivity;③Gating.

1.经通道易化扩散(facilitateddiffusionviachannel)17

Gating（门控）:

1)Voltage-gatedionchannel

2)Chemically-gatedionchannel

3)Mechanically-gatedionchannel离子通道的门控特性示意图182.经载体易化扩散Facilitateddiffusion

viacarrierGlucoseTransporter葡萄糖转运体转运物质:水溶性小分子物质,如葡萄糖（右旋）、AA、核苷酸19经载体易化扩散的特点：

①顺浓度差转运,速度比依溶质物理特性预期的快(movesolutesfasteracrossmembrane);②饱和现象(saturation);③结构特异性(highlyspecifictospecificsolutes);④竞争抑制competitiveinhibition米氏常数20（三）主动转运activetransport定义─细胞膜通过本身某种耗能过程，借助细胞膜某些蛋白质的帮助，将非脂溶性物质分子或离子逆电化学梯度差进行的转运。根据转运能量是否直接来源于ATP的不同分为:原发和继发两种主动转运形式。21钠泵抑制剂:哇巴因ouabain钠-钾泵sodium-potassiumpump

简称钠泵sodiumpump,

又称Na+-K+-ATP酶(Na+-K+-ATPase)1.原发性主动转运PrimaryActiveTransport22①胞内高钾,为代谢提供必需条件（e.g.,核糖体合成蛋白）;②维持胞质渗透压和细胞容积的稳定;③是细胞产生生物电的前提条件；④生电性(排出3Na+,转入2K+)作用,增大膜内负电位,影响静息电位的数值；⑤建立钠的跨膜浓度梯度，为继发性主动转运提供动力（Na+-H+交换，Na+-Ca2+交换）。钠泵（钠钾泵）活动的生理意义23同向转运体（Symporter）反向转运体（Antiporter）2.继发性主动转运(secondaryactivetransport)

某物质逆差转运(主动转运)所需的能量不直接来自ATP的分解,而是来自另一物质主动转运形成的势能贮备(主要是钠泵活动形成的Na+在膜两侧的浓度势能差)。24（1）同向转运近端肾小管上皮（Na+-Glucose）小肠黏膜上皮（2Na+-Glucose）Na+-葡萄糖同向转运体25（1）同向转运Na+-氨基酸肾小管上皮细胞肾小管上皮细胞甲状腺上皮细胞26（1）反向转运Exchangers(alsoknownasantiporters)arefoundinmanydifferentcellsandtissuesandperformavarietyofimportantphysiologicalfunctions.Threeexamplesareshownhere.27肠黏膜上皮细胞葡萄糖继发性主动转运模式图28Howaboutlargemolecules?Movinglargemoleculesinto&outofcellthroughvesicles消耗能量、主动Exocytosis-出胞=themovementofasubstancebyavesicletotheoutsideofacellConstitutiveExocytosis-持续性出胞RegulatedExocytosis-调节性出胞endocytosis–入胞=themovementofasubstanceintoacellbyavesiclephagocytosis

–吞噬=“cellulareating”Pinocytosis-吞饮=“cellulardrinking”（四）膜泡运输（Vesiculartransport）29301.出胞（Exocytosis)

Largemoleculesthataremanufacturedinthecellarereleasedthroughthecellmembrane.InsideCellCellenvironment3031ExocytosisExocyticvesicleimmediatelyafterfusionwithplasmamembrane.copyrightcmassengale31Exocytosis:regulatedandconstitutivesecretion.Duringsecretion,vesiclesderivedfromthetransfaceoftheGolgicomplexwillfusewiththeplasmamembrane,dumpingtheircontentsintotheextracellularenvironment.Inconstitutivesecretion,secretoryvesiclesarecontinuouslydeliveredtotheplasmamembrane,wheretheyrapidlyfusewiththemembrane.Inregulatedsecretion,thevesiclesderivedfromthetransfaceoftheGolgicomplexaggregateandconcentratetheircontentsinthecytoplasm,wheretheyremainuntilthecellhasreceivedtheappropriatesignal.Then,thesecretoryvesiclesfusewiththeplasmamembrane.Thecontentsofthesetwoclassesofsecretoryvesiclesaredistinct.（1）持续性出胞ConstitutiveExocytosis（2）调节性出胞RegulatedExocytosis例：小肠黏膜杯状细胞分泌黏液例：动作电位达到神经末梢引起神经递质的释放32（1）Phagocytosis（吞噬）Usedtoengulflargeparticlessuchasbacteria,etc.intovesicles(Celleating)2.入胞（Endocytosis）3334PhagocytosisAbouttoOccurcopyrightcmassengale34CellformsaninvaginationMaterialsdissolveinwatertobebroughtintocellCalled“CellDrinking”（2）吞饮(Pinocytosis)3536受体介导的入胞Receptor-mediatedendocytosis3738液态镶嵌模型双噬性分子磷脂胆固醇表面蛋白整合蛋白单纯扩散易化扩散离子通道离子选择性化学