Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Membrane Structure 1Chapter 5:Membrane StructureTopics you are not responsible for:details of Na-K pump (fig 5-15)End of Chapter questions:Understand: allApply: all Synthesize: 1 & 2Do all mQuiz questionsMembrane Structure 2What causes Cystic Fibrosis?Symptoms: -- Lungs: mucous accumulation infections-- affects other organs alsoMutation to “CFTR” CF-Transmembrane-Conductance Regulator 1480 amino acidsglycoprotein Membrane Cl- channelMutation alters water transport -- How? -- Why?Membrane Structure 3What is Osmosis?How does solute concentrationaffect osmosis?TonicityOsmotic pressureHow does osmotic pressure affect cells?Turgor pressureSolutions are isotonicOsmosisQuestionMembrane Structure 4How do we know that phospholipids are arranged as a bilayer?Langmuir Trough exp – 1925-- creates monolayerUsed RBCs: (lack internal membranes)Surface area of 1 ml of RBCs= 5x109 cells x 130 um2 / cell = 650 mm2 (~25 cm2)Actually observed ~1300 mm2 Why?QuestionMembrane Structure 5What is the structure of cell membranes?Phospholipids“Amphipathic”Spontaneously form bilayerModelsQuestionMembrane Structure 6What are some key characteristics of cell membranes?Selectively permeableContain other componentsproteinsother lipidscholesterolFluidity-- a “2 dimensional fluid”Membrane Structure 7What factors determine how fluid a membrane is?Properties of P-lipids: Chain length and FA saturationProperties of membranes: Cholesterol contentTemperatureModelsMembrane FluidityMembrane Structure 8How does Alcoholism affect RBC function?Cholesterol contentSpur cell formationFunction and circulation problemsCholesterolQuestionMembrane Structure 9Why can some molecules diffuse through a membrane, and others cannot?SizeChargeHydrophobicityMembrane Structure 10How do molecules passThrough the membrane?Protein transportershigh selectivityVesicular (bulk) transport-- discussed more laterSpecialized Poresgap-junctions & plasmodesmatanuclear poresMembrane Structure 11What are some properties of membrane proteins?Transmembrane (Integral) vs peripheralWhat are some functions of membrane proteins? ModelsHydrophilic & hydrophobicdomainsQuestionMembrane Structure 12What is facilitated transport?Channel transport proteinsa selective poreCarrier transport proteinhas binding sitesPassive Down a concentration gradientActiveAgainst a gradientRequires energyDirection ReversibleMembranetransporterMembrane Structure 13Where does the energy come from for active transport?ATPe.g. Na/ K pumpSunlight (unusual)e.g. bacteriorhodopsinGradient via CotransportBuild and use a ion gradientCotransportQuestionMembrane Structure 14Example: glucose cotransport in intestineNa/glucose symport-- active glucose-- against gradientNa/K pump-- remove NaGlucose uniport-- down gradientMembrane Structure 15What types of molecules pass membranes via “Bulk Transport”?Particulates/ dissolved moleculesVarious formsEndocytosis vs exocytosisPhagocytosisPinocytosisCan be “Receptor mediated”Vesicle “coating” proteinsVesicle CoatingReceptorsMembrane Structure 16How is the structure of membranes studied – I ?Freeze-fracture electron microscopyTissue frozenEtchedCarbon-coatedTEMChloroplast thylakoid membranesMembrane Structure 17How is the structure of membranes studied – II ?Detergentsamphipathticsolubilize