Chapter 7Fluid Mosaic Model: Scientific InquirySlide 3The Fluidity of MembranesSlide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Water balance in cells with wallsSlide 19Slide 20Slide 21Slide 22Slide 23Slide 24You should now be able to:Slide 27PowerPoint Lectures for Biology, Eighth EditionNeil Campbell and Jane ReeceChapter 7Chapter 7Membrane Structure and FunctionPhospholipidbilayerHydrophobic regionsof proteinHydrophilicregions of proteinFluid Mosaic Model: Scientific Inquiry•Freeze-fracture studies of the plasma membrane supported the fluid mosaic model •Freeze-fracture is a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayerTECHNIQUEExtracellularlayerKnifeProteinsInside of extracellular layerRESULTSInside of cytoplasmic layerCytoplasmic layerPlasma membraneThe Fluidity of Membranes(a) Movement of phospholipidsLateral movement(107 times per second)Flip-flop( once per month)•Proteins in the plasma membrane–Can drift within the bilayerEXPERIMENT Researchers labeled the plasma membrane proteins of a mouse cell and a human cell with two different markers and fused the cells. Using a microscope, they observed the markers on the hybrid cell.Membrane proteinsMouse cellHuman cellHybrid cellMixedproteinsafter1 hourRESULTSCONCLUSION The mixing of the mouse and human membrane proteins indicates that at least some membrane proteins move sideways within the plane of the plasma membrane.Figure 7.6+Fig. 7-5b(b) Membrane fluidityFluidUnsaturated hydrocarbontails with kinksViscousSaturated hydro-carbon tailsThe Fluidity of MembranesCholesterol(c) Cholesterol within the animal cell membrane The Fluidity of MembranesFig. 7-7Fibers ofextracellularmatrix (ECM)Glyco-proteinMicrofilamentsof cytoskeletonCholesterolPeripheralproteinsIntegralproteinCYTOPLASMIC SIDEOF MEMBRANEGlycolipidEXTRACELLULARSIDE OFMEMBRANECarbohydrateFig. 7-8N-terminusC-terminus HelixCYTOPLASMICSIDEEXTRACELLULARSIDEFig. 7-9(a) TransportATP(b) Enzymatic activityEnzymes(c) Signal transductionSignal transductionSignaling moleculeReceptor(d) Cell-cell recognitionGlyco-protein(e) Intercellular joining(f) Attachment to the cytoskeleton and extracellular matrix (ECM)Fig. 7-10ER1TransmembraneglycoproteinsSecretoryproteinGlycolipid2GolgiapparatusVesicle34SecretedproteinTransmembraneglycoproteinPlasma membrane:Cytoplasmic faceExtracellular faceMembrane glycolipidFig. 7-11Molecules of dyeMembrane (cross section)WATERNet diffusionNet diffusionEquilibrium(a) Diffusion of one soluteNet diffusionNet diffusionNet diffusionNet diffusionEquilibriumEquilibrium(b) Diffusion of two solutesLowerconcentrationof solute (sugar)Fig. 7-12H2OHigher concentrationof sugarSelectivelypermeablemembraneSame concentrationof sugarOsmosisFig. 7-13Hypotonic solution(a) Animal cell(b) Plant cellH2OLysedH2OTurgid (normal)H2OH2OH2OH2ONormalIsotonic solutionFlaccidH2OH2OShriveledPlasmolyzedHypertonic solutionFilling vacuole 50 µm(a) A contractile vacuole fills with fluid that enters from a system of canals radiating throughout the cytoplasm.Contracting vacuole (b) When full, the vacuole and canals contract, expelling fluid from the cell.Fig. 7-UN3Environment:0.01 M sucrose0.01 M glucose0.01 M fructose “Cell” 0.03 M sucrose0.02 M glucoseFig. 7-UN4Water balance in cells with wallsH2OH2OH2OH2OTurgid (normal) FlaccidPlasmolyzedEXTRACELLULAR FLUID Channel protein (a) A channel protein Solute CYTOPLASM Solute Carrier protein (b) A carrier protein2EXTRACELLULARFLUID [Na+] high [K+] low [Na+] low [K+] highNa+ Na+ Na+ Na+ Na+ Na+ CYTOPLASM ATP ADP P Na+ Na+ Na+ P 3K+ K+ 6K+ K+ 54K+ K+ P P 1Fig. 7-16-7Fig. 7-17Passive transport Diffusion Facilitated diffusion Active transport ATPFig. 7-18EXTRACELLULARFLUID H+ H+ H+ H+ Proton pump + + + H+ H+ + + H+ – – – – ATPCYTOPLASM –Fig. 7-19Proton pump – – – – – – ++++++ATPH+H+H+H+H+H+H+H+Diffusionof H+Sucrose-H+cotransporter Sucrose SucroseEXTRACELLULARFLUIDPseudopodiumCYTOPLASM“Food” or other particleFoodvacuole1 µmPseudopodiumof amoebaBacteriumFood vacuoleAn amoeba engulfing a bacterium viaphagocytosis (TEM).PINOCYTOSISPinocytosis vesiclesforming (arrows) ina cell lining a smallblood vessel (TEM).0.5 µmIn pinocytosis, the cell “gulps” droplets of extracellular fluid into tinyvesicles. It is not the fluiditself that is needed by the cell, but the molecules dissolved in the droplet. Because any and all included solutes are taken into the cell, pinocytosisis nonspecific in the substances it transports.PlasmamembraneVesicleIn phagocytosis, a cellengulfs a particle by Wrapping pseudopodia around it and packaging it within a membrane-enclosed sac large enough to be classified as a vacuole. The particle is digested after the vacuole fuses with a lysosome containing hydrolytic enzymes. •Three types of endocytosisFigure 7.20PHAGOCYTOSIS0.25 µmRECEPTOR-MEDIATED ENDOCYTOSISReceptorLigandCoat proteinCoatedpitCoatedvesicleA coated pitand a coatedvesicle formedduringreceptor-mediatedendocytosis(TEMs).PlasmamembraneCoatproteinYou should now be able to:1. Define the following terms: amphipathic molecules, aquaporins, diffusion2. Explain how membrane fluidity is influenced by temperature and membrane composition3. Distinguish between the following pairs or sets of terms: peripheral and integral membrane proteins; channel and carrier proteins; osmosis, facilitated diffusion, and active transport; hypertonic, hypotonic, and isotonic solutionsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings4. Explain how transport proteins facilitate diffusion5. Explain how an electrogenic pump creates voltage across a membrane, and name two electrogenic pumps6. Explain how large molecules are transported across a cell membraneCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin
View Full Document
Unlocking...