细胞质膜结构和膜上运输.pptx

PlasmaMembraneStructureandFunctionFluid-mosaicmodelofmembranestructureCellsliveinfluidenvironments,withwaterinsideandoutsidethecell.Hydrophilic(water-loving)polarheadsofthephospholipidmoleculeslieontheoutward-facingsurfacesoftheplasmamembrane.Hydrophobic(water-fearing)nonpolartailsextendtotheinterioroftheplasmamembrane.Plasmamembraneproteinsmaybeperipheralproteinsorintegralproteins.Asidefromphospholipid,cholesterolisanotherlipidinanimalplasmamembranes;relatedsteroidsarefoundinplants.Cholesterolstrengthenstheplasmamembrane.Whenphospholipidshavecarbohydratechainsattached,theyarecalledglycolipids.Whenproteinshavecarbohydratechainsattached,theyarecalledglycoproteins.Carbohydratechainsoccuronlyontheexteriorsurfaceoftheplasmamembrane.Theoutsideandinsidesurfacesoftheplasmamembranearenotidentical.ChannelproteinCarrierproteinCellrecognitionproteinInanimalcells,thecarbohydratechainsofcellrecognitionproteinsarecollectivelycalledtheglycocalyx.Theglycocalyxcanfunctionincell-to-cellrecognition,adhesionbetweencells,andreceptionofsignalmolecules.Thediversityofcarbohydratechainsisenormous,providingeachindividualwithauniquecellular“fingerprint”.ReceptorproteinEnzymaticproteinThePermeabilityofthePlasmaMembraneHowmoleculescrosstheplasmamembraneMovementofmaterialsacrossamembranemaybepassiveoractive.Passivetransportdoesnotusechemicalenergy;diffusionandfacilitatedtransportarebothpassive.Activetransportrequireschemicalenergyandusuallyacarrierprotein.Exocytosisandendocytosistransportmacromoleculesacrossplasmamembranesusingvesicleformation,whichrequiresenergy.DiffusionProcessofdiffusionGasexchangeinlungsoccursbydiffusionOsmosisOsmosisdemonstrationOsmosisincellsOsmosisinplantandanimalcellsHypotonicsolutionscausecellstoswellandpossiblyburst.“Hypo”meanslessthan.Animalcellsundergolysisinhypotonicsolution.Increasedturgorpressureoccursinplantcellsinhypotonicsolutions.Plantcellsdonotburstbecausetheyhaveacellwall.Hypertonicsolutionscausecellstolosewater.“Hyper”meansmorethan;hypertonicsolutionscontai