Chapter 5Slide 2Homeostasis Does Not Mean EquilibriumHomeostasis: Fluid CompartmentsOsmosisOsmosis and osmotic pressureSlide 7Slide 8Osmolarity and TonicityTransport ProcessesMembrane TransportDiffusion: PropertiesFick’s law of diffusionFunctions of Membrane ProteinsMembrane ProteinsMembrane receptor proteinsChannelsMembrane TransportersChannel ProteinsFacilitated diffusionNa+-K+-ATPaseCarrier-Mediated TransportPhagocytosisEndocytosis, Exocytosis, and Membrane RecyclingSlide 25Epithelial TransportElectricity ReviewMembrane PotentialSlide 29Equilibrium PotentialsSlide 31Resting membrane potentialSlide 33Chapter 5•Osmosis and tonicity•Transport processes•Diffusion•Protein-mediated transport•The resting membrane potential•Vesicular transport•Epithelial transport•The resting membrane potential© 2013 Pearson Education, Inc.KEYIntracellular fluidInterstitial fluidPlasmaIntracellular fluid is 2/3 of thetotal body water volume. Materialmoving into and out of the ICF must cross the cell membrane.Extracellular fluid includes allfluid outside the cells. The ECF is1/3 of the body fluid volume.The ECF consists of:• Interstitial fluid (IF), which lies between the circulatory system and the cells, is 75% of the ECF volume.• Plasma, the liquid matrix of blood, is 25% of the ECF volume. Substances moving between the plasma and interstitial fluid must cross the leaky exchange epithelium of the capillary wall.Body Fluids – 2 compartments in osmotic equilibrium but differing chemical composition Extracellular fluid (ECF) = 1/3 total body water volumeECF = Interstitial fluid + plasma Intracellular fluid (ICF) = 2/3 total body water volumeHomeostasis Does Not Mean Equilibrium •Osmotic equilibriumWater moves freely between cells and ECFFluid concentrations are equal on two sides of cell membrane•Chemical disequilibriumConcentrations of solutes are different across cell membranes (Na+, Cl-, HCO3- more concentrated in ECF vs ICF) – requires energy to maintain•Electrical disequilibriumMany solutes are ions – carry chargeInside of cells slightly negative relative to ECF© 2013 Pearson Education, Inc.Homeostasis: Fluid CompartmentsKEYIntracellular fluid Interstitial fluid PlasmaIon concentration (mmol/L)16014012010080604020ProteinsHCO3ClKNaThe body compartments are in a state of chemicaldisequilibrium. The cell membrane is a selectivelypermeable barrier between the ECF and ICF.Hi in ECFLo in ECFHi in ECFHi in ECFHi in plasmaOsmosis•Movement of water across a membrane in response to a solute concentration gradient•Osmotic pressure•Molarity versus osmolarity•Osmolarity versus osmolality•Isosmotic, hyperosmotic, and hyposmotic•Tonicity versus osmolarity•Isotonic, hypertonic, and hypotonic•Penetrating versus nonpenetrating solutes© 2013 Pearson Education, Inc.Osmosis and osmotic pressureA BSolution B is moreconcentrated thansolution A.SelectivelypermeablemembraneVolumedecreasedVolumeincreasedGlucosemoleculesForce is applied toB to exactly opposeosmosis from A to B.VolumesequalTwo compartments areseparated by a membranethat is permeable to waterbut not glucose.Water moves byosmosis into the moreconcentrated solution.Osmotic pressure isthe pressure that must beapplied to B to opposeosmosis.Water can move freely across nearly all cells via channels called AQUAPORINS +Solutes cannot freely crossOsmotic EquilibriumWater moves to equalize its concentrationOSMOSIS = movement of water across a membrane in response to a solute concentration gradientOSMOSIS depends on the number of particles in solutionOSMOLARITY = number of osmotically active particles/liter = osmoles/literOsmolarityNormal osmolarity 280-296 mosm/l (or mOsM)Osmolality = mosm/kg useful for estimating from wt TONICITY describes what a solution will do to cell volumeTonicityOsmolarity and TonicityHyperosmoticHyposmoticIsosmoticHypertonicIsotonicHypotonicTONICITYOSMOLARITYOsmolarity depends on the particle number in solutionTonicity describes a solution and how a cell would behave if placed in that solutionCell swellsCell shrinksTransport Processes•Bulk flow–Fluids are gases and liquids–Pressure gradients•Transport across a selectively permeable membrane–Permeable versus impermeable–Passive transport versus active transport–Concentration gradients© 2013 Pearson Education, Inc.Membrane TransportENERGY REQUIREMENTSPHYSICAL REQUIREMENTSMEMBRANE TRANSPORTUses energy ofmolecular motion.Does not require ATP.Requires energyfrom ATP.SimplediffusionFacilitateddiffusionMoleculegoes throughlipid bilayer.SecondaryactivetransportMediated transportrequires amembrane protein.DiffusionPrimaryactivetransportUses amembrane-boundvesicle.createsconcentrationgradientforEndocytosisExocytosisPhagocytosisDiffusion: Properties1. Passive process2. High concentration to low concentration–Chemical gradient3. Net movement until concentration is equal–Equilibrium4. Rapid over short distances5. Directly related to temperature6. Inversely related to molecular weight and size7. In open system or across a partition© 2013 Pearson Education, Inc.Fick’s law of diffusionFick’s Law of DiffusionMembrane PermeabilityFactors affecting rate of diffusionthrough a cell membrane:Changing the composition of the lipid layer canincrease or decrease membrane permeability.Membrane permeabilitylipid solubilitymolecular sizeRate of diffusion surface area concentration gradient membrane permeability• Lipid solubility• Molecular size• Concentration gradient• Membrane surface area• Composition of lipid layerConcentrationinside cellConcentrationgradientConcentrationoutside cellMolecularsizeLipidsolubilityMembranesurface areaCompositionof lipid layerIntracellular fluidExtracellular fluidDiffusion rate = concentration gradient X membrane permeability = fluxFunctions of Membrane Proteins•Structural proteins•Enzymes•Membrane receptor proteins•Transporters–Channel proteins–Carrier proteins© 2013 Pearson Education, Inc.Membrane ProteinsMEMBRANEPROTEINSStructure Functioncan be categorized according toare found inactivateare active inare active informopen andclosechangeconformationIntegralproteinsPeripheralproteinsMembranetransportersStructuralproteinsMembraneenzymesMembranereceptorsCarrierproteinsChannelproteinsReceptor-mediatedendocytosisSignaltransferMechanicallygatedchannelVoltage-gatedchannelChemicallygatedchannelOpen channelsGated channels MetabolismCell junctions
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