Cellular Transport Notes

Cellular TransportNotes@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyAbout Cell Membranes All cells have a cellmembrane Functions:– Controls what entersand exits the cell tomaintain an internalbalance calledhomeostasis– Provides protection andsupport for the cellTEM picture of areal cell membrane.@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey1

About Cell Membranes (continued) 1.Structure of cell membraneLipid Bilayer -2 layers ofphospholipids Phosphate head is polar(water loving) Fatty acid tails non-polar(water fearing) Proteins embedded inmembranePhospholipidLipid Bilayer@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyPolar heads Fluid Mosaiclove waterModel of the& dissolve. cell membraneNon-polartails hidefrom water.Carbohydrate cellmarkersProteins@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey2

About Cell Membranes (continued) 4. Cell membranes have pores (holes) in it Selectively permeable: Allows somemolecules in and keeps other molecules out The structure helps it be selective!Pores@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyStructure of the Cell MembraneOutside of tProteinPhospholipidsInside of cell(cytoplasm) @ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey3

Types of Cellular Transport Passive Transportcell doesn’t use energy1. Diffusion2. Facilitated Diffusion3. Osmosis Active Transportcell does use energy1. Protein Pumps2. Endocytosis@ 2011for Pre-College3. CenterExocytosisPrograms, New Jersey Institute ofTechnology, Newark, New JerseyPassive Transport cell uses no energymolecules move randomlyMolecules spread out from an area ofhigh concentration to an area of lowconcentration. (High Low) Three types:@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey4

3 Types of Passive Transport DiffusionFacilitative Diffusion – diffusion with thehelp of transport proteinsOsmosis – diffusion of water@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyPassive Transport:1. DiffusionSimple DiffusionAnimation Diffusion: random movementof particles from an area ofhigh concentration to anarea of low concentration.(High to Low) Diffusion continues until allmolecules are evenly spaced(equilibrium is reached)-Note:molecules will still move aroundbut stay spread @out.2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jerseyhttp://bio.winona.edu/berg/Free.htm5

Passive Transport:2. Facilitated Diffusion2. Facilitated diffusion:diffusion of specific particlesthrough carrier proteinsfound in the membrane Carrier Proteins arespecific – they “ select” only certain moleculesto cross the membrane Transports larger orcharged molecules ABFacilitateddiffusion(ChannelProtein) Diffusion(LipidBilayer) @ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofhttp://bio.winona.edu/berg/Free.htmTechnology, Newark, New JerseyCarrier ProteinPassive Transport: 2. Facilitated DiffusionCellular Transport From aHigh ConcentrationHighGlucosemolecules Channel ProteinsanimationsCell MembraneProteinchannelLow ConcentrationLowThrough a Go toSection:TransportProtein@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey6

Facilitated DiffusionIon Channels Transport ions from high concentration tolow concentration Transport ions such as Sodium (Na )Potassium(K ), Calcium(Ca 2 ), andChloride(Cl -) Because ions are not soluble in Lipids, theycannot diffuse across the bilayer. Ion channels will open and close in order toallow specific molecules to cross the@ 2011 Center for Pre-Collegemembrane. Programs, New Jersey Institute ofTechnology, Newark, New JerseyPassive Transport:3. OsmosisOsmosisanimation 3.Osmosis: diffusion ofwater through aselectively permeablemembrane Water moves from highto low concentrations Water moves freelythrough pores. Solute (green) to largeto move across.@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey7

Active Transport cell uses energy actively moves molecules to where they areneeded Movement from an area of low concentrationto an area of high concentration (Low High) Three Types:@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyTypes of Active Transport1. Protein Pumps transport proteins thatrequire energy to dowork Example: Sodium /Potassium Pumpsare important in nerveresponses.SodiumPotassium Pumps(Active Transportusing proteins) Protein changesshape to movemolecules: thisrequires energy!@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey8

Sodium Potassium Pump 1. Sodium ions bind to the carrier protein onthe cytoplasm side of the membrane whilethe carrier protein removes the phosphategroup from the ATP 2. The phosphate group binds to the carrierprotein changing its shape 3. The carrier protein carries the threesodium ions across membrane and forcesthem into the environment@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseySodium Potassium Pump Continued 4. The carrier protein now has the correctshape to carry two potassium ions acrossthe membrane and into the cell; thepotassium ions bind to the carrier proteins 5. The phosphate group (from the ATPearlier) is released, and the carrier originalshape is restored 6. This causes the potassium ions to bereleased into the cytoplasm@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey9

Sodium Potassium PumpSodium Potassium PumpPumps ThreePumps TwoSodium IonsPotassium IonsInto CellOut of the Cell@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyTypes of Active Transport 2. Endocytosis: takingbulky material into a cell Uses energy Cell membrane in-foldsaround food particle “cell eating” forms food vacuole &digests food This is how white bloodcells eat bacteria!@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey10

Types of Active Transport3. Exocytosis: Forcesmaterial out of cell in bulkEndocytosis &Exocytosisanimations membrane surrounding thematerial fuses with cellmembrane Cell changes shape –requires energy EX: Hormones orwastes released fromcell@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyEffects of Osmosis on Life Osmosis- diffusion of water through aselectively permeable membrane Water is so small and there is so muchof it the cell can’t control it’s movement through the cell membrane.@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey11

Hypotonic SolutionOsmosis Animationsfor isotonic,hypertonic, andhypotonic solutionsHypotonic: The solution has a lower concentration ofsolutes and a higher concentration of water thaninside the cell. (Low solute; High water) Result: Water moves from the solution to inside thecell): Cell Swells andbursts(cytolysis)!@ 2011Center foropenPre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey Hypertonic SolutionOsmosis Animationsfor isotonic,hypertonic, andhypotonic solutionsHypertonic: The solution has a higher concentrationof solutes and a lower concentration of water thaninside the cell. (High solute; Low water) shrinksResult: Water moves from inside the cell into thesolution: Cell shrinks(Plasmolysis)!@ 2011Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey12

Isotonic SolutionOsmosis Animationsfor isotonic,hypertonic, andhypotonic solutionsIsotonic: The concentration of solutes in the solutionis equal to the concentration of solutes inside the cell.Result: Water moves equally in both directions andthe cell remains same size! (Dynamic Equilibrium) @ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New JerseyWhat type of solution are these cells in?ABCHypertonicIsotonicHypotonic@ 2011 Center for Pre-CollegePrograms, New Jersey Institute ofTechnology, Newark, New Jersey13

How Organisms Dealwith Osmotic Pressure Bacteria and plants have cell walls that prevent themfrom over-expanding. In plants the pressure exerted onthe cell wall is called tugor pressure. A protist like paramecium has contractile vacuoles thatcollect water flowing in and pump it out to prevent themfrom over-expanding. Salt water fish pump salt out of their specialized gills sothey do not dehydrate. Animal cells are bathed in blood. Kidneys keep the@ 2011 Centerfor Pre-Collegeblood isotonic by removeexcesssalt and water.Programs, New Jersey Institute ofTechnology, Newark, New Jersey14

Types of Cellular Transport Passive Transport cell doesn’t use energy 1. Diffusion 2. Facilitated Diffusion 3. Osmosis Active Transport cell does use energy 1. Protein Pumps 2. Endocytosis @ 2011 3. Center for Pre Exocytosis-College Programs, New Jersey Institute of Technology, Newark, New Jersey Passive