浙师大《细胞生物学》第五章_物质的跨膜运输与信号传递

《浙师大《细胞生物学》第五章_物质的跨膜运输与信号传递》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。

1、第五章物质的跨膜运输与信号传递•主要内容：•第一节物质的跨膜运输•第二节细胞通讯与信号传递第一节物质的跨膜运输•、被动运输(passivetransport)1、概念：是通过简单扩散或协助扩散实现物质由高浓度向低浓度方向的跨膜运转。2、特点:1)运输方向：高低；2)跨膜动力：物质的浓度梯度；3)能量消耗：无简单扩散：不需要4)膜转运蛋白：协助扩散：需耍3、类型：简单扩散、协助扩散4^简单扩散(Simplediffusion)1)概念：又称为自由扩散(freediffusion),是疏水小分子或小的不带电荷的极性分子，不需要能量也不需要膜蛋白参与的跨膜运输方式。2)

2、特点：①沿浓度梯度(或电化学梯度)扩散；②不需要提供能量；③没有膜蛋白的协助。•Simplediffusionmeansthatthemoleculescanpassdirectlythroughthemembrane・Diffusionisalwaysdownaconcentrationgradient.Thislimitsthemaximumpossibleconcentrationofthemoleculeinsidethecell(oroutsidethecellifitisawasteproduct).Theeffectivenessofdiffusio

3、nisalsolimitedbythediffusionrateofthemolecule・Therefore,thoughdiffusionisaneffectiveenoughtransportmechanismforsomesubstances(suchasH2O),thecellmustutilizeothermechanismsformanyofitstransportneeds.5、协助扩散(faciliuneddiffusion)1)概念：也称促进扩散，是极性分子和无机离子在膜转运蛋白协助下顺浓度梯度(或电化学梯度)的跨膜运输。2)特点：①转运速率高

4、；②存在最大转运速率；③有膜转运蛋白参与，有特异性.••Facilitateddiffusionutilizesmembraneproteinchannelstoallowchargedmolecules(whichotherwisecouldnotdiffuseacrossthecellmembrane)tofreelydiffuseinandoutofthecell・ThesechannelscomesintogreatestusewithsmallionslikeK+,Na+,andC1-.Thespeedoffacilitatedtransportisli

5、mitedbythenumberofproteinchannelsavailable,whereasthespeedofdiffusionisdependentonlyontheconcentrationgradient.6、膜转运蛋门(TransportProtein)1)载体蛋白(carrierproteins)通透fW(permease)性质；介导被动运输与主动运输。1)通道蛋门(channelproteins)——具有离子选择性，转运速率高；离子通道是门控的；只介导被动运输类型：a电压门通道(vollage・gatedchannel)b配体门通道(liga

6、nd-gatedchannel)c压力激活通道(stress-activatedchannel)TransportProteinscomeintwoforms:1)Carrierproteins:Theseareearnerproteins.Theydonotextendthroughthemembrane・Theybondanddragmoleculesthroughthebilipidlayerandreleasethemontheoppositeside.2)Channelproteins:extendthroughthebilipidlayc匚Theyfo

7、rmaporethroughthemembranethatcanmovemoleculesinseveralways.Insomecasesthechannnelproteinssimplyactasapassivepore.Moleculeswillrandomlymovethroughtheopeninginaprocesscalleddiffusion.Thisrequiresnoenergy,moleculesmovefromanareaofhighconcentrationtoanareaoflowconcentration.二.主动运输(activet

8、ransp