Chapter 4 Membrane Structure and Function. Plasma Membrane

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Transcript of Chapter 4 Membrane Structure and Function. Plasma Membrane

Chapter 4

Chapter 4Membrane Structure and Function

Plasma MembraneFluid Mosaic ModelCholesterolReduces the amount of stuff allowed to enter a cellPhospholipids This is the lipid bilayerGlycolipids A carbohydrate that is attached to a phospholipidProteinsCan help move things in and out of the cellGlycoproteinsA carbohydrate that is attached to a protein

The carbohydrates that come out of the plasma membrane allow cells to recognize each otherIf a cell is not recognized the body tries to kill that foreign cell

Permeability of Plasma MembranePlasma membrane is selectively permeableSelective PermeabilitySelective permeability- Some things are let into the cell while some things remain outside of the cell

Concentration GradientThere is a greater concentration of small balls on one side than the other. This means that it will try to reach an equilibrium.A gradient means that there is more on one side and gets less and less as you move to the other sideDiffusionDiffusion is the movement of molecules from a higher concentration to a lower concentration

TimeSemi-PermeableDiffusionThis occurs in our lungs.High concentration of oxygen air enters lungs and O2 diffuses into our blood, which has a lower concentration of oxygenOsmosisOsmosis is the diffusion of waterWater moves from a high concentration to a low concentration

Water moves to the right because there is a difference in concentrationOsmotic pressure is the pressure that develops in a system because of osmosis

Factors that will affect the rate of DiffusionTemperature higher temp. the faster the rate of diffusionSize of molecule the smaller the molecule then the faster the rate of diffusionCharge of molecule charged molecules have difficulty moving through the cellConcentration Gradient the larger the difference in concentration the faster the diffusionPressure Gradient If there is pressure on one side then the faster the diffusionWhat happens to a cell in a solutionTonicity concentration of the solution compared to the concentration inside the cellIsotonic The concentration of the solution is equal to that of inside the cellHypotonic Solution has a lower concentration of solute (higher concentration of water) than inside the cellHypertonic Solution has higher concentration of solute than inside the cellWhat happens to a cell in solutionIsotonic solutionThe cell remains the same. No changesHypotonic solutionThe cell swells and may undergo lysisHypertonic solutionThe cell loses water and shrivels. Or undergoes crenationWhich is which?

Hypertonic IsotonicHypotonicFacilitated TransportThis is for molecules that are too big to diffuse through the plasma membraneProteins help them moveIt stills move with the concentration gradientIt uses NO ENERGY

DiffusionFacilitated TransportFacilitated TransportDiffusionOsmosisNone of these use EnergySo therefore they are called Passive TransportActive TransportThis uses energyATP ADPIt moves molecules and ions against a concentration gradientAn example of active transport is the sodium potassium pumpSodium is moved to the outside and potassium is moved to the inside of the cell

Endocytosis and ExocytosisThese processes are used for materials that are too big to pass through the plasma membrane by a protein transportEndocytosisThe cell engulfs material to bring it into the cellTwo typesPhagocytosisPinocytosisExocytosisMoves material to the outside of the cellThis allows cell to secrete moleculesEndocytosisPhagocytosisA type of endocytosis that engulfs large items. Like cells or bacteriaThe vesicle that forms afterwards combines with lysosomes so digestion can occur

EndocytosisPinocytosisThis is when very small particles are engulfed by the membraneReceptor mediated endocytosis is a type of pinocytosis that uses receptor proteins to help initiate pinocytosis