考研复旦-细胞学姐3.biomem

2023/1/211Chapter

3:BiomembraneCellSurfaceAnd2023/1/212Outline3.0Introduction3.1ComponentsandStructureofBiomembranes

3.2PlasmaMembrane3.3TransmembraneTransport3.4CellJunctionandAdhesionMolecules3.5ExtracellularMatrixandCellWall2023/1/2133.0IntroductionAllcellssurroundedbyalayerofmembraneIneukaryotecell,membranecompartmentalizethecellintosomesmallerpartmentstermedorganellesInprokaryotecell,lackspartment2023/1/214eukaryoteandprokaryotecell

(SeeChapter1)2023/1/215Themembrane-enclosedorganellesincytoplasmofeukaryoteORGANELLEDESCRIPTIONCytoplasm*Semifluidmediumsurroundedbyplasmamembrane,allorganellesfloatinthemediumNucleusThelargestandmostimportantorganellesurroundedbytwolayerofmembraneandcontainedchromatin,nucleolus,nuclearlamina,nuclearmatrixandafewRNAEndoplasmicReticulum(ER)Anetworkofinterconnectedmembranoustubulesthatcontainsspecificenzymes;smoothER(sER)lacksribosomesbutitisimportantforthesynthesisofspecialmoleculessuchasthelipidsrERisstuddedwithribosomesthatmakeproteinsGolgiApparatusStacksofmembranoussacscontainingspecialenzymesthatmodify,storeandshipproductsfromtheERtothecellmembraneorotherpartsofeukaryoticcellsLysosomesOrganellethatsurroundedbysinglelayerofmembraneandcontainsenzymesthatdigestfoodandwastesineukaryoticcellsVacuolesAmembraneenclosedsacthathasdiversefunctionsineukaryoticcells,storesubstances,thecentralvacuoleinplantcellsChloroplastsorganellethatisenclosedbytwolayersofmembranes(aninnerandanoutermembrane);chloroplastsabsorbsunlightandtomakefoodmolecules(sugars)byphotosynthesisMitochondrionAnorganellethatisenclosedbytwolayersofmembranes(aninnerandanoutermembrane);aeukaryoticorganellethatplaysimportantrolesincellularrespiration;mitochondriaproduceATPwhichisthefuelthecellusesforitsvariousactivities.*Cytoplasmisnotsuggestedasorganelleandnotonlyineukaryoticcell.

2023/1/216ThelocationofmainfunctionsineukaryoteMainfunctionsCytologicallocationLocalizationandorganizationoffunctionPlasmamembraneandorganellesRegulationofmaterialstransportPlasmamembraneDetectionandtransmissionofsignalPlasmamembraneandnuclearmembraneDNAreplicationandtranscription*NucleusmembraneIntercellularinteractionsPlasmamembraneEnergytransductionMitochondrionandChloroplastProteinssynthesisandtransportRoughendoplasmicreticulumandgolgibodyLipidssynthesisandtransportSmoothendoplasmicreticulumCarbohydratemetabolismCytoplasmandmitochondrionetal.ResistinganddepositionVacuole(inplantcell)*LocalizationofDNAreplicationandtranscriptiononplasmamembraneinprokaryoticcells

2023/1/217Outlineofcellsurfacecellwallcellcoatandextracellularmatrix2023/1/2183.1ComponentsandStructureof

Bio-membranesBasiccompositionslipidsproteins

saccharide.2023/1/219Thebasiccompositionsofsomebio-membranes

MembraneProteins(%)Lipids(%)Saccharide(%)PlasmamembraneRedbloodcell49438Myelinmembrane18793Livercell543610Nucleusmembrane66322Golgibody642610Endoplasmicreticulum622710MitochondrionOutsidemembrane5545traceInsidemembrane7822-Chloroplast7030-2023/1/21103.1.1Lipidsinbio-membrane

Phospholipid磷脂(Phosphoglycerides磷酸甘油酯和Sphingomyelin鞘磷脂

sphingolipids(神经)鞘脂类steroids

胆固醇amphipathicmolecules(两性分子）hydrophobicgrouppolarheadgroup2023/1/2111Phosphoglycerides（磷酸甘油酯）XPC:phosphatidylcholine卵磷磷（脂酰胆碱）X=cholinePE:phosphatidylethanolamine磷脂酰乙醇胺X=ethanolaminePS:phosphatidylserine

磷脂酰丝氨酸X=serine

2023/1/2112phosphatidylcholine2023/1/2113Theclassofsphingolipids(

鞘脂）2023/1/2114Sphingomyelin

(SM)

sililarwithphosphatidylcholine2023/1/2115◆胆固醇(Cholesterol)■胆固醇存在于真核细胞膜中：●动物细胞膜胆固醇的含量较高●Cholesterolisabsentfromtheplasmamembranesofmostplant.

●酵母细胞膜中是麦角固醇;■胆固醇分子包括三部分:

●极性的头部：羟基●非极性的类固醇环结构●一个非极性的碳氢尾部。■Cholesterolissmallerthantheotherlipidsofthemembraneandlessamphipathic（两性分子的）.

2023/1/2116Cholesterol2023/1/2117Lipidscompositionsofsomebiomembranes

Source/LocationComposition(mol%)PCPE+PSSMCholesterolPlasmamembrane(humanerythrocytes)21292126Myelinmembrane(humanneurons)16371334Plasmamembrane(E.coli)08500Endoplasmicreticulummembrane(rat)542657Golgimembrane(rat)45201313Innermitochondrialmembrane(rat)454527Outermitochondrialmembrane(rat)3446211PrimaryleafletlocationExoplasmicCytosolicExoplasmicBoth2023/1/2118phosphoLipidmakeupofbasicframeworkofbio-membrane

2023/1/21193.1.2Proteinsinbio-membrane

Threeformsproteinslinktomembrane

Integralproteins(Transmembraneproteins)Lipid-anchoredmembraneproteinsPeripheralmembraneproteinsStructureproteinsEnzyme2023/1/2120proteinsassociatewiththelipidbilayer

2023/1/2121IntegralproteinsCytosolicdomainExoplasmicdomainTransmembranedomainhydrophilicsurfacesstuddedinmembraneinteractwiththeaqueoussolutionsinteractwiththehydrocarboncoreofthephospholipidbilayerbindtoothermoleculesorionsanchoringcytoskeletalproteinstriggeringintracellularsignalingpathwaysformchannelsandporesglycosylatedlocalizedtotheexoplasmicdomains2023/1/2122Lipid-anchoredmembraneproteinscovalentboundtolipidmoleculesofthephospholipidbilayer.polypeptidechaindoesnotenterthephospholipidbilayer.Peripheralmembraneproteinsboundtothemembraneindirectlybyinteractionswithintegralmembraneproteinsordirectlybyinteractionswithlipidheadgroups.localizedtoeitherthecytosolicortheexoplasmicfaceoftheplasmamembrane.2023/1/2123proteinsoncellmembranecanbeclassedto:Channelproteins:toformporesforthefreetransportofsmallmoleculesandionsacrossthemembrane;Carrierproteins:tofacilitateddiffusionandactivetransportofmoleculesandionsacrossthemembrane;Cellrecognitionproteins:toidentifiesaparticularcell;Receptorproteins:tobindspecificmoleculessuchashormonesandcytokinesandEnzymaticproteins:thatcatalyzespecificchemicalreactions.2023/1/21243.1.3Membranecarbohydrate2%~10%inmembranedependonthedifferenceofcellscovalentcombinewithmembraneproteinsandformglucoproteinsallmembranecarbohydratepitchontheoutsideofplasmamembrane.

2023/1/2125kindsofmembranecarbohydrate

D-glucoseD-galactoseD-mannoseL-fructoseN-acetyl-D-galactosamineN-acetyl-glucosaminesilicacid.2023/1/21262023/1/2127ABOBloodTypeAntigen2023/1/2128functionofmembranecarbohydrate1)

Improvethestabilityofmembranes2)

Advancethefastnessoftoproteinase3)Helpmembraneproteinstoformcorrectthree-dimensionalconfigure4)

Cellsignalrecognition,celladhensionandcelljunction5)

Correctpositionfortransferofnewprotein6)

Lectin,protectthecellandseed7)Bloodgroupdeterminants2023/1/21293.1.4MembraneAsymmetryThetwohalvesofthebilayeroftencontaindifferenttypesofphospholipidsandglycolipids.Theproteinsembeddedinthebilayerhaveaspecificorientation2023/1/2130Theasymmetryofthelipidbilayerwasfoundbytakingadvantageoflipid-digestingenzymesthatcannotpenetratetheplasmamembraneandsubsequentlyareonlyabletodigestlipidsthatresideintheexternalmonolayerofthebilayer2023/1/2131Ineucaryoticcells,thelipidasymmetryisproducedatthepointofmanufacture.2023/1/21323.1.5MembraneFluidityMembranefluidityisessentialformembranefunction:Allowsmoleculestodiffuserapidlycellmovement,cellgrowth,celldivision,secretionetcFirstdemonstratedin1970byLarryFryeandMichaelRestrictionsonproteinmobilityLipidsprovidethematrixinwhichintegralproteinsofamembraneareembedded,thusthephysicalstateofthelipidisimportantindeterminingthemobilityofintegralproteins2023/1/2133Twodifferenttypesofcellscanbefusedtoproduceonecellwithacommoncytoplasmandasinglecontinuousplasmamembrane.Seemtoshowthatintegralmembraneproteinswerecapableofmovingfreely.

2023/1/2134

◆淋巴细胞的成帽效应

通过抗体交联膜蛋白分子聚集成斑(patching)、成帽(capping)的现象也是膜蛋白在膜平面侧向扩散的例子。2023/1/2135成帽反应?2023/1/2136However,furtherstudiesusingFRAP:(fluorescencerecoveryafterphotobleaching,荧光漂白恢复）therearerestrictionsonproteinmobility.

Therateofthefluorescencerecovery2023/1/2137SPT（single-particletracking,单颗粒示踪技术）:individualmembraneproteinmoleculesarelabeledthenthemovementsofthelabeledmoleculesaremonitoredTheresultsindicatesthatmostproteinmoleculesrandommovementatratessimilartofreediffusion(diffusioncoefficientsabout5×10-9cm2/sec)thedistanceisrestrictedtoafewtenthsofamicron.Long-rangediffusionoccursbutatslowerrates.Insomecases,certainproteinsmoveinahighlydirected(nonrandom)mannertowardonepartofthecelloranother.Somemembraneproteinshardlymoveandareconsideredtobeimmobilized.2023/1/2138Typesofmovementdiffusionandrotationmorefrequentandrapidthan“flip-flop”Individuallipidmoleculerotateveryrapidlyaroundtheirlongaxis(30,000rpm)phospholipiddiffusefromoneendtotheotherwithinoneortwosecondphospholipidmovingacrosstotheothermonolayercantakehourstodays“Flip-flop”(amovementofmoleculesfromonehalfofamonolayertotheotherhalf)ismostrestricted.2023/1/2139Thepossiblemovementsofphospholipidsinamembrane.

2023/1/2140Thephysicalstateofthelipidofamembrane◆相变温度（transitiontemperature）

在生理条件下,膜脂多呈拟液态（liquid-likestate）。温度下降至某点,则变为晶态（frozencrystallinegel）。一定温度下,晶态又可熔解再变成液晶态，这种临界温度称为相变温度。◆相变(phasetransition)

在不同温度下发生的膜脂状态的改变称为相变。不同的膜脂由于成分不同而各有其相变温度。2023/1/2141

Factorsofinfluencebilayerfluidity

◆脂肪酸链的影响

膜脂肪酸链对流动性的影响主要是不饱和程度和链的长短：■Thegreaterthedegreeofunsaturationofthefattyacidsofthebilayer,thelowerthetemperaturebeforethebilayergels.

■Theshorterthefattyacylchainsofaphospholipid,theloweritsmeltingtemperature.

2023/1/2142◆胆固醇的影响■cholesterolmoleculesareorientedwiththeirsmallhydrophilichydroxylgrouptowardthemembranesurfaceandtheremainderofthemoleculeembeddedinthelipidbilayer.

■Thehydrophobicringsofacholesterolmoleculeareflatandrigid,andtheyinterferewiththemovementsofthefattyacidtailsofthephospholipids■在相变温度以上,它可使磷脂分子的脂酰链末端的运动减小,即限制膜的流动性。■在相变温度以下,可增加脂类分子脂酰链的运动,这样可以增强膜的流动性。2023/1/2143胆固醇对流动性的影响?2023/1/2144◆卵磷脂/鞘磷脂比值的影响■哺乳动物膜中,卵磷脂(phosphatidycholine)和鞘磷脂(sphingomyelin)的含量约占整个膜脂的50%;■卵磷脂所含的脂肪酸链的不饱和程度高,链较短,相变温度低,因此卵磷脂含量高,流动性大;■而鞘磷脂的脂肪酸链的饱和程度高,相变温度也高,因此,鞘磷脂的含量高,流动性低。2023/1/2145◆影响膜蛋白移动的因素■整合蛋白相互间的影响■膜骨架的影响■细胞外基质的影响■相邻细胞的影响■细胞外配体、抗体、及药物大分子的影响2023/1/2146细胞外基质对整合蛋白移动的影响2023/1/2147膜骨架对膜蛋白流动性的影响2023/1/21483.2PlasmaMembrane

(cellmembrane)

allcellsaresurroundedbyplasmamembraneabc2023/1/21493.2.1.OverviewofPlasmaMembrane

Outsideandinteriorsideofcellmembranecytosolicfaceexoplasmicface2023/1/2150Proteinsandglycoproteinsoncellmembrane2023/1/2151Plantcellwallandplasmamembrane

2023/1/2152bacterialcellwallandcytoplasmicmembrane2023/1/2153Plasmamembraneisasemipermeableapurephospholipidbilayer

2023/1/21543.2.2CommonfunctionsofplasmamembraneActaspermeabilitybarrier

IntimatelyengagedintheassemblyofcellwallsFormspecificjunctionsbetweencellsAnchorcomponentsoftheextracellularmatrixContainreceptorproteinsthatbindspecificsignalingmoleculesTakepartinthecompartmentalizationofcellEnergytransduction2023/1/21553.3TransmembraneTransport

plasmamembrane:Themostimportantstructuretotransmembranetransportinanycells.Selectivepermeabilityoftheplasmamembraneallowsthecelltomaintainaconstantinternalenvironment.(enterthecell,leavethecell,remaininthecell)Theplasmamembranesofdifferentcellcontainsaspecificsetoftransportproteinsthatallowonlycertainionsandmoleculestocross.mostmoleculesandallionsmovesacrosscellularmembranesmediatedbyselectivemembranetransportproteins

embeddedinthephospholipidbilayer.2023/1/21563.3.1Overviewoftrans-membranetransportPropertyPassiveDiffusionFacilitatedDiffusionActiveTransportCotransport*SpecifictransportproteinNoRequireRequireRequireRequireSolutetransportedagainstitsgradientNoNoyesyesCoupledtoATPhydrolysisNoNoyesNoDrivenbymovementofaiondownitsgradientNoyesNoyesExamplesO2,CO2,steroidhormones,manydrugsGlucoseandaminoacids(uniporters);ionsandwater(channels)Ions,smallhydrophilicmolecules,lipids(ATP-poweredpumps)Glucoseandaminoacids(symporters);variousionsandsucrose(antiporters)2023/1/2157PASSIVETRANSPPORT

OFSUBSTANCESPassivetransport◆顺浓度梯度◆不消耗ATP◆根据需不需要膜蛋白的帮助,被动运输又可分为:■自由扩散■帮助扩散。2023/1/21583.3.2Passivediffusion(simplediffusion)suggestthatsuchmoleculescandiffuseacrosscellularmembraneswithouttransportproteins.O2,CO2

ureaandethanolsteroidhormones,drugsCandiffuseacrossanartificialmembranesIntheprocess,nometabolicenergyisexpended,nospecifictransportproteinsneed,themoleculesmovedownitschemicalconcentrationgradient.2023/1/2159Passivediffusiondrivedbythethermodynamicaction.Diffusionrateisdeterminedby:concentrationgradientacrossthelayerhydrophobicitysizeelectricpotentialacrossthemembrane2023/1/2160■虽然这种移动不需要消耗ATP，主要是依靠扩散物质自身的力量，但从热力学考虑，它利用的是自由能。

■如果改变膜两侧的条件，如加热或加压，就有可能改变物质的流动方向，其原因是改变了自由能。

■严格地说，扩散是物质从自由能高的一侧向自由能低的一侧流动。2023/1/2161扩散2023/1/21623.3.3FacilitatedDiffusionOverviewoffacilitateddiffusionpolarmolecules,ionsandwater,transportacrossmembranewithfacilitatedexhibitsthefollowingdistinguishingpropertiesfrompassivediffusion:TherateisfarhigherthanpassivediffusionThepartitioncoefficientKisirrelevantOccursviaalimitednumberofuniportermoleculesTransportisspecific.

2023/1/2163Membraneproteinsmediatetransport

transportproteinschannelproteinstransporters2023/1/2164Channelproteinswater,ionsandhydrophilicsmallmoleculesdown

concentrationorelectricpotentialgradients.assistdiffusionformahydrophilicpassagewayacrossthemembrane2023/1/2165通道蛋白(Channelproteins)

目前发现的通道蛋白已有50多种，主要是离子通道(ionchannels)。◆nongated

channels:openmuchofthetime◆gated

channels:openonlyinresponsetospecificchemicalorelectricalsignals闸门通道(gatedchannels)，是通道蛋白进行的间断开放通道。2023/1/2166Typicalgatedchannels

2023/1/2167■配体闸门通道（Ligand-gatedchannels）

■电位闸门通道（Voltage-gatedchannels）

■牵张闸门通道（Stretch-gatedchannels)

这种通道的打开受一种力的作用，听觉毛状细胞的离子通道就是一例。声音的振动推开胁迫激活通道，允许离子进入毛状细胞，这样建立起一种电信号，并且从毛状细胞传递到听觉神经，然后传递到脑。2023/1/2168Someexamplesofionchannels

ChannelLocationFunctionsK+leakagechannelTheplasmamembraneofmostanimalsKeeprestingpotentialVoltage-gatedNa+channelTheplasmamembraneofneuralaxonProduceactionpotenpialVoltage-gatedK+channelTheplasmamembraneofneuralaxonResumerestingpotentialafterstartingactionpotenpialVoltage-gatedCa2+channelTheplasmamembraneofnerveterminalActivatereleasingofnervetransmitterAcetylcholineacceptorAcetylcholine-gatedNa+andCa2+channel)Theplasmamembraneofmusclecells(Thelink-endofnerveandmuscle)Excitablesynaptictransmissionofsignals(transformchemicalsignaltoelectriconeintargetcells)GABAacceptor(GABA-gatedCl-channel)Theplasmamembraneofmanynervecells(atsynapse)InhibitorysynaptictransmissionofsignalsStress-gatedpositiveionchannelAuditoryhaircellsininnerearDetectthejutterofvoice2023/1/2169Transporters(carriers)moleculeoriontransportedlinktothetransporter,Eachkindoftransporterlinkstospecialsolution-moleculechangingtheconformationofitselfThreetypes:Uniporters,antiportersandsymporters2023/1/2170Atypicalexample-----GLUT12023/1/2171ModelofglucosetransportintoerythrocytesbyGLUT12023/1/2172离子载体(Ionophores)

由微生物产生的脂溶性抗生素。◆缬氨霉素(Valinomycin)●由12个氨基酸组成的环状肽；●一种可动离子载体(mobileioncarrier),插入脂质体后，能特异性运输K+,使运输速率提高100000倍。2023/1/2173◆短杆菌肽A(GramicidinA)●一种形成通道的离子载体(channelformingcarrier)；●由15个氨基酸组成的线性肽,两个分子在一起形成跨膜的通道；●它能够有选择地将单价阳离子按电化学梯度通过膜，但并不显著提高运输速度；●可被短杆菌肽A离子通道运输的阳离子有∶H+

NH4+

K+

Na+

Li+。2023/1/2174Energychangespanyingpassageofahydrophilicsolutethroughthelipidbilayer2023/1/21753.3.4Activetransportmediatedbyaspecificmembraneproteins,tooagainst

theirconcentrationgradientneedtheenergysupplyLightelectrochemicalgradientLightpoweredpump2023/1/2176(1)ATP-PoweredPumps

Fourclasses:P,V,FandABC(ATP-bindingcassettetransporter)EnergysupplyiscoupledtothehydrolysisofATPSimplypumps2023/1/2177ExamplesoffourclassesofATPpumps

ClassExamplesP-ClassPlasmamembraneofplants,fungi,bacteria(H+pump),Plasmamembraneofhighereukaryotes(Na+/K+pump),Apicalplasmamembraneofmammalianstomach(H+/K+pump),Plasmamembraneofalleukaryoticcells(Ca2+pump),Sarcoplasmicreticulummembraneinmusclecells(Ca2+pump)V-ClassVacuolarmembranesinplants,yeast,otherfungi,Endosomalandlysosmalmembranesinanimalcells,Plasmamembraneofosteoclastsandsomekidneytubulecells.F-ClassBacterialplasmamembrane,Innermitochondrialmembrane,ThylakoidmembraneofchloroplastABC-ClassBacterialplasmamembranes(aminoacid,sugar,andpeptidepermeases),Mammalianplasmamembranes(transportersofphospholipids,smalllipophilicdrugs,cholesterol,othersmallmolecules)2023/1/2178(2)Cotransporterstwotypes:symporterandantiportercoupledtoanenergeticallyfavorablereactionusetheenergystoredinanelectrochemicalgradientThekeepingoftheseelectrochemicalgradientssecondary

activetransport.2023/1/2179twotypesofcarriersenablegutepithelialcellstotransferglucoseandaminoacidacrossthegutlining消化道被覆2023/1/2180Comparativeofsymportsinanimalandplantcells2023/1/21813.3.5SeveraltopicforionpumpsGenerateandMaintainIonicGradientsAcrossCellularMembranesCa2+IonsintotheSarcoplasmicReticulumfromtheCytosolMaintainstheIntracellularNa+andK+ConcentrationsinAnimalCellsPumpProtonsAcrossMembranesandacidifythelumenBacterialPermeasesAreABCProteinsThatImportVarietyNutrientsABCSmall-MoleculePumpsinMammalsMovementofWater2023/1/2182GenerateandMaintainIonicGradientsAcrossCellularMembranesTheioniccompositionofcytosolandextracellularfluidTheionpumps,now,arelargelyresponsibleforestablishingandmaintainingtheusualionicgradientsacrosstheplasmaandintracellularmembranes.2023/1/2183TypicalIntracellularandExtracellularIonConcentrations

IonCell(mM)Blood(mM)Squidaxon(Invertebrate)*

K＋40020Na＋50440Cl40–150560Ca2+0.000310X-**300–4005–10Mammalian(vertebrate)

K+1394Na+12145Cl-4116HCO3-1229X1389Mg2+0.81.5Ca2+0.00021.82023/1/2184P-typeATPase◆Na+-K+pump,Na+-K+ATPase●又称Na+泵或Na+/K+交换泵，或Na+-K+ATP酶；●Na+-K+ATPase是由两个大亚基(α亚基)和两个小亚基(β亚基)组成；●α亚基是跨膜蛋白，在细胞质面有ATP结合位点，细胞外侧有鸟本苷(ouabain)结合位点;●在α亚基上有Na+和K+结合位点。2023/1/2185钠-钾泵的结构2023/1/2186MaintainsIntracellularNa+andK+ConcentrationsinAnimalCells2023/1/2187◆Ca2+pump,Ca2+ATPase●TheCa2+-ATPasepresentinboththeplasmamembraneandthemembranesoftheendoplasmicreticulum.●Ca2+

泵的工作原理类似于Na+-K+

泵:

在细胞质面有同Ca2+结合的位点，一次可以结合两个Ca2+，Ca2+结合后使酶激活，并结合上一分子ATP，伴随着ATP的水解酶被磷酸化，Ca2+泵构型发生改变，结合Ca2+的转到细胞外侧被释放，此时酶发生去磷酸化，构型恢复到原始的静息状态。2023/1/2188StructureofCa2+ATPase★2023/1/2189●Ca2+-ATP酶激活机制▲Ca2+/钙调蛋白复合物的作用

当细胞内Ca2+浓度升高时，Ca2+同钙调蛋白结合，形成活性复合物，该复合物同抑制区结合，释放激活位点，泵开始工作。▲蛋白激酶C的作用

蛋白激酶C使抑制区磷酸化，从而解除抑制作用；▲由上可以看出，在Ca2+-ATP酶的羧基端有三个功能位点(区域)∶同激活位点结合区、同

CaM结合区、磷酸化位点。

2023/1/2190Ca2+intoSarcoplasmicReticulumfromtheCytosol2023/1/2191StructureofthecatalyticαsubunitofthemuscleCa2+

ATPase

2023/1/21922023/1/2193PumpProtonsAcrossMembranesandacidifythelumenba2023/1/2194BacterialPermeasesAreABCProteinsThatImportVarietyNutrients2023/1/2195ABCSmall-MoleculePumpsinMammals2023/1/2196Movementofwater渗透(Osmosis)◆Watermovesreadilythroughasemipermeablemembranefromaregionoflowersoluteconcentrationtoaregionofhighersoluteconcentration.Thisprocessiscalledosmosis,◆水的渗透同样是从自由能高的地方向自由能低的地方移动，如果考虑到溶质的浓度，水是从溶质浓度低的地方向溶质浓度高的地方流动。

2023/1/2197

waterchannelHypotonicsolution低渗:CellSwellHypertonicsolution:Shrinkandplasmolysis（质壁分离)IsotonicsolutionHowtomaintaincellvolumnNa+-K+pump:netexportofcationstopreventswelling(3Na+outfor2K+)

2023/1/21982023/1/21993.4CellJunctionandAdhesionMolecules

细胞黏着概述◆概念：在细胞识别的基础上,同类细胞发生聚集形成细胞团或组织的过程。◆在细胞识别过程中,细胞的糖被起重要作用，而引起细胞黏着的主要是膜蛋白。2023/1/21100◆细胞黏着的方式2023/1/21101凝集素在细胞黏着中的作用2023/1/21102Celljunctions:tightjunctionanchoringjunctions锚定连接gapjunction间隙连接Plasmodesmata胞间连丝Celladhesion:cadherins钙粘素intergrins整联蛋白selectins选择素

immunoglobulinThecadherinsoftenmediatethestablecelljunction.2023/1/21103CellAdhesionMoleculesFamilyLigandsrecognizedStablecelljunctionCadherinsHomophilicinteractions同嗜性互作AdherensjunctionsanddesmosomesIntegrinsExtracellularmatrixFocaladhesionsandhemidesmosomesMembersofIgsuperfamilyNoSelectinsCarbohydratesNoIgIntegrinsNosuperfamilyHomophilicinteractionsNo2023/1/21104Majorfamiliesofcell-adhesionmolecules(CAM)

2023/1/21105

紧密连接的存在部位和结构特点◆又叫不通透连接(impermeablejunction),它不仅连接相邻的细胞,而且封闭细胞间隙,使大多数分子难以在细胞间通透。◆这种连接方式普遍存在于腔道上皮细胞靠近管腔端的相邻细胞膜间。◆从结构上看,通过连接蛋白形成焊接线，封闭相邻细胞间的空隙。3.4.1TightJunction(封闭）2023/1/21106Acurrentmodelofatightjunction

紧密蛋白颗粒形成连接线2023/1/21107紧密连接的功能◆连接作用◆维持细胞的极性

防止物质双向渗漏，并限制了膜蛋白在脂分子层的流动2023/1/21108紧密连接与细胞极性2023/1/211093.4.2AnchoringJunction锚定连接◆又称斑形成连接(plaque-bearingjunction)◆主要靠黏着蛋白、整联蛋白和细胞骨架体系将相邻两细胞或细胞与细胞外基质连接在一起。◆斑形成连接分为：

●adhesion黏着连接

●desmosome桥粒2023/1/21110AnchoringJunction

（粘着）2023/1/21111

黏着连接

(adherenjunction)

细胞间的连接作用与细胞骨架系统的肌动蛋白相关称为黏着连接。

●adhesionbelt黏着带●focaladhesion黏着斑2023/1/21112◆黏着带(adhesionbelts)●是细胞-细胞间黏着的一种方式；●位于上皮细胞紧密连接的下方；●靠钙黏着蛋白同肌动蛋白相互作用；●黏着带处相邻细胞质膜的间隙为20～25nm,介于紧密连接和桥粒之间。2023/1/21113■参与黏着连接的组分∶●黏着蛋白(cadherin)∶

一种跨膜连接糖蛋，属Ca2+

依赖的细胞-细胞黏着分子，它有三个结构域●细胞质斑(cytoplasmicplaque)∶

含黏着斑蛋白(vinculin)，连环蛋白（catenin）等，介导肌动蛋白与黏着蛋白相连；●肌动蛋白∶2023/1/21114Adhesionbelts2023/1/21115◆黏着斑

(adhesionplaqua，focaladhesion)

主要特点是：

肌动蛋白纤维通过整联蛋白同细胞外基质，如纤粘连蛋白，而不是与另一个细胞的表面相连。Cell-extracellularjunction2023/1/21116Focaladhesion2023/1/21117桥粒(desmosomes)◆细胞是通过中间纤维锚定到细胞骨架上，这种黏着连接方式称为桥粒。◆分为：

●(点状)桥粒●半桥粒。2023/1/21118Desmosomes

2023/1/21119◆Hemidesmosomes

半桥粒与桥粒连接有两点差别∶●半桥粒参与连接的跨膜蛋白不是钙黏着蛋白而是整联蛋白；●整联蛋白的细胞外结构域不是与相邻细胞的整联蛋白相连而是同细胞外基质相连。2023/1/21120Hemidesmosomes2023/1/21121Hemidesmosomes2023/1/21122黏着连接的作用2023/1/21123Asummaryofjunctionalandnonjunctionaladhesivemechanisms.

2023/1/211243.4.3CommunicationJunction◆一种特殊的细胞连接,位于特化的具有细胞间通讯作用的细胞

◆具机械的细胞连接作用◆在细胞间形成电偶联或代谢偶联,以此来传递信号

◆通讯连接的方式：●GapJunction间隙连接●plasmodesmata胞间连丝2023/1/21125GapJunction

constructedofconnexins(连接蛋白）Sixconnexinsassembletoformaconnexon（连接子withanopenhydrophilicporeinitscenterconnexoninonecellalignswiththeconnexonofadjacentcellformingachannel.

2023/1/211262023/1/21127◆间隙连接的主要功能：●机械连接作用；●Electricalcoubling：createmetabolicandelectricalcouplingbetweenthecells电偶联在神经冲动信息传递过程中起重要作用；●Mateboliccoubling

playkeyrolesinboththemetabolicactivitiesandsignalingsofthecellstheyconnect(M.W.<1000Dolton)代谢偶联可允许小分子代谢物和信号分子通过间隙连接2023/1/21128胞间连丝(plasmodesma)◆胞间连丝的结构∶●是相邻植物细胞壁上的一个狭窄细胞壁通道●有管状的内质网通过。因此，通过胞间连丝，使得相邻细胞的细胞质膜、细胞质、内质网交融在一起●胞间连丝直径约30-60nm，允许1000道尔顿以下的分子渗透。2023/1/21129plasmodesmata(胞间连丝)2023/1/211303.5ExtracellularMatrixandCellWall

Extracellularmatrix(ECM)isnonlivingmaterialaroundcellsinmulticellularorganisms.importanceincell-cellsignaling,woundrepair,celladhesionandtissuefunctionprimarilycomposedofcelluloseinplants,composedofchitininarthropods(节肢动物）andfungi,carbohydratesandproteinsinvertebrates能够分泌和形成细胞外基质的主要细胞类群是成纤维细胞(fibroblast)和其他特化组织的细胞。ThreemostobviousformsofECMarebone,cartilageandbasementmembrane.2023/1/21131TypicalExtracellularmatrix2023/1/21132◆细胞外基质的组成可分为三大类∶●蛋白聚糖(proteoglycan)●结构蛋白如胶原和弹性蛋白，它们赋予基质一定的强度和韧性。●黏着蛋白(adhesiveproteins)

如纤连蛋白和层粘蛋白，它们促使细胞同基质结合。2023/1/211334.2.1细胞外基质的基础物质蛋白聚糖(Proteoglycan,PG)◆结构与功能

●

Protein-polysaccharidecomplexiscalledaproteoglycan

●Aproteoglycanconsistsofacoreproteinmoleculetowhichchainsofglycosaminoglycans(GAGs,糖胺聚糖)arecovalentlyattached.●BecauseofthenegativechargesborneonthesulfatedGAGs,proteoglycansbindhugenumbersofcations,whichinturnbindlargenumbersofwatermolecules.Asaresult,proteoglycansformaporous,hydratedgelthatfillstheextracellularspacelikepackingmaterialandresistscrushing(compression)forces.

2023/1/21134Proteoglycan2023/1/21135◆透明质酸(hyaluronicacid)

细胞外基质中发现的大多数糖胺聚糖都是作为蛋白聚糖的一个成分而存在，惟一例外的是透明质酸，它在细胞外

基质中也可游离存在。

透明质酸在结缔组织中起强化、弹性和润滑作用,具有抗压能力。2023/1/21136

结构蛋白胶原(Collagen)◆基本特性：●Collagenisafamilyoffibrousglycoproteinsthatarepresentonlyinextracellularmatrices.●Collagenisthesinglemostabundantproteininthehumanbody(constitutingmorethan25percentofallp