大学生物课讲义ppt模板之噬菌体chapter

Chapter4MembraneFunction3.MembraneFunctionTransportofMoleculesSignalTransductionWorkingcellsmustcontroltheflowofmaterialstoandfromtheenvironment.•Membraneproteinshelpwiththistask,theyarethecustomagentsofthecells.HerearesomefunctionsofproteinmembranesCELL1CELL2PermeabilityofthePlasmaMembrane•Somemoleculesfreelycrossmembrane–Water,small,nonchargedmolecules–Watermayalsouseaquaporinstocrossmembrane•Othermoleculescannot–use…–Channelproteins–Carrierproteins–Vesicles•EndocytosisorexocytosismacromoleculeH2Oprotein++--chargedmoleculesandionsphospholipidmoleculenonchargedmoleculesCopyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.MoleculescanpassthroughthemembranethroughdifferentmechanismsA.PassiveTransport:DiffusionAcrossMembranesB.OsmosisandWaterBalanceC.ActiveTransportD.ExocytosisandEndocytosis:TrafficofLargeMoleculesPassageofMoleculesIntoandOutoftheCell–Diffusionisoneresultofthemovementofmolecules.•Moleculestendtospreadintotheavailablespace.•Diffusionispassivetransport;NOenergyisneeded.–Moleculescontainheatenergy.Theyvibrateandmovearound.A.PassiveTransport:DiffusionAcrossMembranes–Anothertypeofpassivetransportisfacilitateddiffusion,thetransportofsomesubstancesbyspecifictransportproteinsthatactasselectivecorridors.•Gasescandiffusethroughamembrane•OxygenandcarbondioxideenterandexitthiswayCopyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.capillaryalveolusbronchioleoxygenO2O2O2O2O2O2O2O2O2O2O2O2Severalfactorsinfluencetherateofdiffusion–Temperature•Astemperatureincreases,therateofdiffusionincreases–Pressure–Electricalcurrents–MolecularsizeB.OsmosisandWaterBalanceinCellsOsmosisisthepassivetransportofwateracrossaselectivelypermeablemembrane.Osmosis–Diffusionofwateracrossadifferentiallypermeablemembrane–Diffusionalwaysoccursfromhighertolowerconcentration–Osmoticpressureisthepressurethatdevelopsinasystemduetoosmosis•Thegreaterthepossibleosmoticpressure,themorelikelyitisthatwaterwilldiffuseinthatdirection–Ahypertonicsolution•Hasahigherconcentrationofsolute.–Ahypotonicsolution•Hasalowerconcentrationofsolute.–Anisotonicsolution•Hasanequalconcentrationofsolute.WaterBalanceinAnimalCells–Thesurvivalofacelldependsonitsabilitytobalancewateruptakeandloss.–Osmoregulationisthecontrolofwaterbalanceinanimals.WaterBalanceinPlantCells–Waterbalanceinplantcellsisdifferent.•Theyhaverigidcellwalls.•Theyareatthemercyoftheenvironment.C.ActiveTransport:ThePumpingofMoleculesAcrossMembranesActivetransportrequiresenergytomovemoleculesacrossamembrane.–Carrierproteinsarespecific•Combinewithamoleculeoriontobetransportedacrossthemembrane–Carrierproteinsarerequiredfor:•FacilitatedTransport•ActiveTransportActiveTransport:•Facilitatedtransport–Smallmoleculesthatarenotlipid-soluble–Moleculesfollowtheconcentrationgradient–EnergyisNOTrequiredCopyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.InsideplasmamembranecarrierproteinsoluteOutside•ActiveTransport–Moleculescombinewithcarrierproteins•Oftencalledpumps–Moleculesmoveagainsttheconcentrationgradient•Enteringorleavingcell–EnergyisrequiredK+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+PPPPInside6.Changeinshaperesultsandcausescarriertorelease2K+insidethecell.carrierproteinOutsideK+K+K+ADPATPK+K+K+3.Changeinshaperesultsandcausescarriertorelease3Na+outsidethecell.2.ATPissplit,andphosphategroupattachestocarrier.4.Carrierhasashapethatallowsittotakeup2K+.5.Phosphategroupisreleasedfromcarrier.1.Carrierhasashapethatallowsittotakeup3Na+.Sodium-PotassiumPumpDiffusionFacilitatedDiffusionOsmosisInsidethecellCytoplasmPassiveNoenergyActiveEnergyINSUMMARYATPD.ExocytosisandEndocytosis:TrafficofLargeMoleculesMechanismsthatinvolvefusionwiththeplasmamembraneanduseofvesicles.Exocytosis(ExoExit)Secretessubstancesoutsideofthecell.EndocytosisTakessubstancesinsideofthecell.ExocytosisEndocytosis•Inphagocytosis(“cellulareating”),acellengulfsaparticleandpackagesitwithinafoodvacuole.•Inpinocytosis(“cellulardrinking”),acell“gulps”dropletsoffluidbyformingtinyvesicles.Differentendocytosis:•Receptor-mediatedendocytosisistriggeredbythebindingofexternalmoleculestomembraneproteins.Copyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.parameciumsolutesolutea.Phagocytosisb.Pinocytosisvacuolecoatedvesicleplasmamembranecoatedpitc.Receptor-mediatedendocytosis399.9µmvesiclevacuoleformingpseudopodofamoeba0.5µmvesiclesformingcoatedvesiclecoatedpitreceptorproteina(right):©EricGrave/Phototake;b(right):©DonW.Fawcett/PhotoResearchers,Inc.;c(both):CourtesyMarkBretscherTheRoleofMembranesinCellSignaling–Cellularcommunication•Beginswiththereceptionofanextracellularsignal.–Thesignaltransductionpathway•Consistsofproteinsandothermoleculesthatrelaythesignal.CellularResponseSignalTransductionPathwayTRUEorFALSE:Facilitateddiffusionrequiresenergytodriveaconcentrationgradient.