Slide 1Animal cell plasma membrane 5.2Fluid Mosaic Model 5.1, 5.2, 5.4Effect of fatty acid composition 3.25a, 3.25b, 5.1Interaction between phospholipid composition and temperatureSlide 6Membrane protein functions 5.6Transmembrane proteins 5.7bTransmembrane proteins 5.7aSlide 10Slide 11Slide 12Review of diffusion 5.9Diffusion of two solutesReview of osmosis 7.14Osmosis and water balance of cells 5.12Osmosis and water balance of cells 5.12Passive transport: simple diffusion From table 5.2Passive transport: facilitated diffusion 7.17Slide 20Membrane Structure and FunctionChapter 5Animal cell plasma membrane 5.2CELL EXTERIORCYTOPLASMCarbohydratePhospholipidsFluid Mosaic Model 5.1, 5.2, 5.4The fluid mosaic model of membrane structure: All biological membranes contain many proteins embedded in the fluid matrix of the lipid bilayerMany membrane proteins diffuse laterally, some anchored by attach-ment to cytoskeleton or extracellular matrixHydrophobic region of proteinHydrophilic regionsof proteinPhospholipidbilayerHydrophilicheadHydrophobictailsMembrane ProteinsEffect of fatty acid composition 3.25a, 3.25b, 5.1FatsPhospholipidMembrane fluidity is impacted by phospholipid compositionLess fluid more fluidUnsaturated fatty acidtails with kinksSaturated fatty acidtailsInteraction between phospholipid composition and temperatureEffect of temperature on membrane fluidity•As the temperatures cools, membranes become less fluid and more viscous as the hydrocarbon tails pack more tightly •At a given temperature (for example, in the cold), membranes with a higher proportion of unsaturated phospholipid are more fluid than those with a lower proportionOrganisms can alter the fatty acid composition of their phospho-lipids to maintain optimal membrane fluidity.Cholesterol also affects membrane integrity and fluidity•restrains phospholipid movement—keeps membranes from being too fluid•maintains fluidity by preventing tight packing of phospholipidshttps://prezi.com/tolczjkgns_z/cell-membrane-structure/Membrane protein functions 5.6Membrane Proteins: major functionsOutsidecellInsidecellCell-surface receptorEnzymeTransporterCell-surface identity marker Cell-to-cell adhesion Cytoskeleton anchorTransmembrane proteins 5.7bTransmembrane proteins--integral membrane proteins that span the membrane•Region spanning the membrane is enriched in nonpolar (hydrophobic) amino acids, often coiled into a-helices•Region protruding into the aqueous environment is enriched in polar or charged amino acids1 structureN-terminusC-terminusStretch of hydrophilic amino acidsStretch of hydrophobic amino acidsN-terminusC-terminusTransmembrane Domaina-helixTransmembrane proteins 5.7aMembrane protein with multiple transmembrane a-helicesMembrane protein with multiple transmembrane a-helices1 structureN-terminusC-terminusStretch of hydrophilic amino acidsStretch of hydrophobic amino acidsN-terminus helixC-terminusLoopMultipleTransmembrane DomainsTransport across biological membranesBiological membranes are selectively permeable.•Hydrophobic (nonpolar) molecules, such as hydrocarbons, CO2, and O2, can penetrate the lipid bilayer and pass through the membrane easily.•Polar molecules, such as sugars and ions, do not cross the membrane easily; their transport is mediated by transport proteins.•Water crosses membranes by osmosis.How solutes cross cellular membranes (video)•Passive transport–Diffusion; net movement of solutes down a concentration gradient–Does not require energy–Can occur by Simple diffusion (no transport proteins involved)Facilitated diffusion (through a transport protein)•Active transport–net movement of solutes against a concentration gradient–Requires energy–Requires a transport proteinMembrane transport videoReview of diffusion 5.9Diffusion -- the tendency of molecules to spread out evenly in the available space by random motionNet direction of diffusion is down the concentration gradient.No net change in concentration once equilibrium is reached.Solute moleculesMembrane (permeable to solute)WATER(a) Diffusion of one soluteNet diffusion Net diffusionEquilibriumDiffusion of two solutesWhen there is more than one solute, each diffuses according to its own concentration gradient.(b) Diffusion of two solutesNet diffusion Net diffusionNet diffusionNet diffusionEquilibriumEquilibriumSolute moleculesMembrane (permeable to solutes)Review of osmosis 7.14Osmosis--diffusion of water across a selectively permeable membrane (permeable to water but impermeable to solute)Lowerconcentrationof solute (sugar)Higher concentrationof soluteSugarmoleculeH2OSame concentrationof soluteSelectivelypermeablemembraneOsmosisWater diffuses from the region of lower solute concentration to the region of higher solute concentrationhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.htmlOsmosis and water balance of cells 5.12Water balance in living cellsOsmosis and water balance of cells 5.12Water balance in living cellsPassive transport: simple diffusion From table 5.2Simple diffusion--diffusion directly across the lipid bilayer•Does not require transport proteins•Nonpolar molecules (O2, CO2)•Very small uncharged polar molecules (e.g. some H2O)Passive transport: facilitated diffusion 7.17Facilitated diffusion: passive transport aided by proteins•Hydrophilic molecules (e.g sugars, amino acids, ions)•Transport proteins are specific for the solutes they transportChannelproteinCarrierproteinAquaporins: channel proteins for H2O--increases membrane permeability to