膜结构及其转运功能

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1、厦门大学医学院戚智SizeofthecellsCellDiversity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)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？FLUID-becauseindividualphospholipidsandproteinscanmoveside-to-sidewithinthela

2、yer,likeit’saliquid.MOSAIC-becauseofthepatternproducedbythescatteredproteinmoleculeswhenthemembraneisviewedfromabove.FLUIDMOSAICMODEL(液态镶嵌模型)Thickness~6nmSinger&Nicholson,1972磷脂PhospholipidsHydrophilic:“waterloving”Hydrophobic:“waterfearing”（一）细胞膜的脂

3、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（二）细胞膜的蛋白MembraneProteinsProteinsdeterminemembrane’sspecificfunctions:Plasmamembrane&organellemembraneseachhaveuniquecollectionsofproteinsMemb

4、raneproteins:peripheralproteins(表面蛋白):resideoutsidehydrophobicregionoflipids,looselyboundtosurfaceofmembraneintegralproteins（整合蛋白）:embeddedwithinbilayer,usuallyacrosswholemembranetransportproteinschannels,permeases(pumps)（三）细胞膜的糖类Membranecarbohydrat

5、esPlayakeyroleincell-cellrecognitionabilityofacelltodistinguishonecellfromanotherantigensimportantinorgan&tissuedevelopmentbasisforrejectionofforeigncellsbyimmunesystemGlycoprotein糖蛋白Glycolipid糖脂MembraneStructure:ProteintoLipidRatiovariesfromcellty

6、petocelltypeRatioforcellswithhighmetabolicactivity功能活跃的细胞，其膜蛋白含量较高52%40%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

7、主动转运；Primaryactivetransport(3)继发性主动转运；Secondaryactivetransport（一）单纯扩散SimpleDiffusion-RequiresNOenergyDiffusionisthenetmovementofmolecules(orions)fromaregionoftheirhighconcentrationtoaregionoftheirlowerconcentration.Themoleculesmovedownaconcentration

8、gradient.Moleculeshavekineticenergy,whichmakesthemmoveaboutrandomly.Asaresultofdiffusionmoleculesreachanequilibriumwheretheyareevenlyspreadout.Thisiswhenthereisnonetmovementofmoleculesfromeitherside.①Highspeed;(106~108/sec)②Selectivity;③Gating.1.经通