Chapter03MembraneStructureCholesterol:Anamphipathiclipidcontainingthefour-ringsteroidstructurewithahydroxylgroupononering;amajorcomponentofmanyeukaryoticmembraneandprecursorandprecursorofsteroidhormones.Integralmembraneprotein:Anyproteinthatcontainsoneormorehydrophobicsegmentsembeddedwithinthecoreofthephospholipidbilayer;alsocalledtransmembraneprotein.Integrins:Alargefamilyofheterodimerictransmembraneproteinsthatfunctionasadhesionreceptors,promotingcell-matrixadhesion,orascelladhesionmolecules,promotingcell-celladhesionLipid:Anyorganicmoleculethatispoorlysolubleorvirtuallyinsolubleinwaterbutissolubleinnonpolarorganicsolvents.Majorclassesincludefattyacids,phospholipids,steroids,andtriglycerides.Lipid-anchoredmembraneprotein:Anyproteinthatistetheredtoacellularmembranebyoneormorecovalentlyattachedlipidgroups,whichareembeddedinthephospholipidsbilayerLipidraft:Microdomainintheplasmamembranethatisenrichedincholesterol,sphingomyelin,andcertainproteins.Lipoprotein:Anylarge,water-solubleproteinandlipidcomplexthatfunctionsinmasstransferoflipidsthroughoutthebody.Seealsolow-densitylipoprotein(LDL).Liposome:Artificialsphericalphospholipidbilayerstructurewithanaqueousinteriorthatformsinvitrofromphospholipidsandmaycontainmembraneproteins.Plasmamembrane:Themembranesurroundingacellthatseparatesthecellfromitsexternalenvironment;consistsofaphospholipidbilayerandassociatedmembranelipidsandproteins.1.Whichofthefollowingisafunctionofmembranes? partmentalization b.selectivelypermeablebarrier c.mediatesintercellularinteractions d.helpscellsrespondtoexternalstimuli e.alloftheabove2.WhatevidenceconvincedOvertonthatmembraneswerecomposedoflipids? a.Hecouldseethelipidsinthemicroscope. b.Membranesweredestroyedbyenzymesthatdegradedlipids. c.Hefoundthatmorelipid-solublesolutesenterroothaircellsfasterthanpolarsolutes d.Membranesdissolvedingasoline. e.Membranesdidnotdissolveinwater.3.GorterandGrendelextractedlipidsfromhumanredbloodcells.Theycalculatedthetotalsurfaceareafortheseredbloodcellsandfoundittobe36μ2.Howmuchsurfaceareawouldtheselipidscoveroncetheywerespreadacrossthesurfaceofwater? a.72μ2 b.36μ2 c.18μ2 d.144μ2 e.30μ24.WhatarrangementdidGorterandGrendelsuggestforlipidsinthecellmembrane? a.asinglelayeroflipids b.alipidbilayerwithphospholipidtailsfacingthewateroneachsurfaceofthemembrane c.alipidbilayerwithphospholipidheadsfacingthewateroneachsurfaceofthemembrane d.alipidtrilayerwithphospholipidheadsfacingthewateroneachsurfaceofthemembrane e.aproteinbilayer5.Whichofthefollowingstatementwasevidencethattheremustbemoretomembranesthanthelipidbilayer? a.Membranesgrew. b.Lipidsolubilitywasnotthesoledeterminantofwhatcanpassthroughamembrane. c.Thesurfacetensionofmembraneswasmuchhigherthanthoseofpurelipidstructures. d.Thesurfacetensionofmembraneswasmuchlowerthanthoseofpurelipidstructures. e.bandd6.WhatdidDavsonandDanielliaddtotheirmodelofenzymestructuretoexplainthepassageofpolarsolutesandionsthroughthemembraneandtoaccountfortheirselectivepermeability? a.Theyproposedprotein-linedpores. b.Theyproposedlipid-linedpores. c.Theyproposedcarbohydrate-linedpores. d.Theyproposedaproteincoatingonthecytoplasmicsurfaceofthemembrane. e.Theyproposedacarbohydratecoatingontheexternalsurfaceofthemembrane.7.HowdidtheSingerandNicolsonFluid-Mosaicmodeldifferfromearliermodelsofmembranestructure? a.Theyproposedthatthelipidsinthemembranearefrozenandimmobile. b.Theyproposedthatproteinsaredistributedinamosaicofdiscontinuousparticlesthatpenetrateintoorthroughthemembraneorinteractwiththepolarheadsofthelipids c.Theyproposedthatindividuallipidsmovelaterallywithintheplaneofamembrane. d.Carbohydratesarealwayslocatedonthecytoplasmicsideofthemembrane. e.bandc8.Whatarethebuildingblocksofaphosphoglyceride,specificallyphosphatidicacid? a.glycerol+2phosphategroups+1fattyacid b.glycerol+1phosphategroup+2fattyacids c.glycerol+1phosphategroup d.glycerol+3fattyacids e.glycerol+1phosphategroup+3fattyacids9.Whatworddescribesthestructuresofcholesterol,phosphoglyceridesandsphingolipids? a.amphoteric b.ambidextrous c.amphipathic d.rings e.straight10.Whatisthenameofamoleculewiththefollowingstructure:sphingosine+fattyacid+galactose? a.acerebroside b.aganglioside c.aphosphoglyceride d.aande e.galactocerebroside16.Membrane-associatedcarbohydratesexhibitamajorasymmetryintheirdistribution.Whatisit? a.Membrane-associatedcarbohydratesfacethecytoplasminallcases. b.Membrane-associatedcarbohydratesfacetowardtheoutsideofcellsintotheextracellularspace. c.Internalcellularmembranecarbohydratesfacetheorganelleinteriorandawayfromthecytosol. d.bandc e.Carbohydratesareonlyassociatedwiththenuclearmembrane.17.Whatislargelyresponsibleforthenegativechargeonmanyoligosaccharidechains? a.asparticacid b.glutamicacid c.sialicacid d.glucose e.galactose18.Whatroleareglycolipidslikegangliosidesthoughttoplayinthecell? a.Theyarethoughttometabolizesugars. b.Theyarethoughttoserveassomekindofreceptor. c.Theyhelptostabilizethemembrane. d.Theyhelptodestroyinfectiousbacteria. e.aandb19.ThecarbohydratesontheredbloodcellmembranesofapersonwiththeABbloodtypewouldhavewhatsugarontheendstheirchains? a.glucose b.N-acetylgalactosamine c.galactose d.maltose e.bandc20.Whatkindofmembraneproteinpenetratesintothehydrophobicpartofthelipidbilayer? egralprotein b.lipid-anchoredprotein c.peripheralproteins d.bandc e.aandb21.Whatkindofmembraneproteinisfoundentirelyoutsidethebilayerontheextracellularorcytoplasmicsurface?Theseproteinsareassociatedwiththemembranesurfacebynoncovalentbonds. egralprotein b.lipid-anchoredprotein c.peripheralproteins d.bandc e.aandb22.Whatkindofmembraneproteinisfoundentirelyoutsidethebilayeroneithertheextracellularorcytoplasmicsurface?Theseproteinsarecovalentlylinkedtoamembranelipidsituatedwithinthebilayer? egralprotein b.lipid-anchoredprotein c.peripheralproteins d.bandc e.aandb23.Whatkindofmembraneproteincannotbewashedfreeofthemembranebyalowionicstrengthsolution? egralprotein b.lipid-anchoredprotein c.peripheralproteins d.bandc e.aandb24.Whatkindofmembraneproteinisnotatallembeddedwithinthehydrophobiccoreofthelipidbilayer? egralprotein b.lipid-anchoredprotein c.peripheralproteins d.aandb e.bandcYouarecharacterizinganisolatedmembraneprotein.Theproteinisexposedonbothsidesofthemembrane.Overmuchofthecentralpartofitssurface,therearehydrophobicaminoacidswhiletheendsarehydrophilic.Itcrossesthemembraneanumberoftimes.Thereisanopeninginthecenterofthisproteinlinedbyhydrophilicaminoacids.Whatkindofproteinisthisandwhatisitsprobablefunction?Itisapolytopicproteinthatprobablyservesasachanneltotransportionsorotherpolarsolutes.6.Youareinvestigatingthetransitiontemperatureofamembrane,theoriginofwhichyoudonotknow.Thetemperatureoftransitionforthismembraneisverysharp,occurringoveranextremelynarrowrangeoftemperatures.Whatcanyousayaboutthecompositionofthemembrane?Itisprobablycomposedofasinglephospholipidor,atmost,twoorthreephospholipids.7.Youdeterminethetransitiontemperaturesfortwomembranes.Thefirsthasatransitiontemperatureof28°C,thesecond15°C.Whatcanyouconcludeaboutthecompositionsofthetwomembranes?Thefirstprobablyhaslipidswithlongerhydrocarbonchainsand/orahigherdegreeofsaturationthanthesecond.8.Amoleculenormallyentersacellbysimplediffusionthroughthelipidbilayer.Whathappensifyouart