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26 Pages

Anatomy and Physiology
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Membrane TransportMembrane has many responsibilities transportation of substances outside the cell to the inside membrane contains receptors used for signal transduction attached to cytoskeleton and extracellular matrixenzymatic activity intercellular joiningcelltocell recognition Plasma Membrane considered fluid because particlessubstances can move freely sidewaysfrom one side to other phospholipid bilayer doesnt allow polar molecules exception of waterLipids phospholipid bilayer hydrophobic inside membrane hydrophilic on outer and inner surfaces glycolipids cover 5 of membrane bonded to sugar moleculescholesterol covers 20 stabilizes membrane involved in formation of lipid rafts lipid raft platform for certain receptor moleculesProteinsProteins are dispersed in the lipid bilayer If not anchored they can freely move around integral proteins embedded in the bilayer important because they link the outside of the cell with the inside carriers receptors channels enzymes go from one end of bilayer to the other peripheral proteins attached loosely to the membraneCarbohydrateslocated primarily on the outer surface of the membranebound to lipids glycolipids or proteins glycoproteins function fuzzy sticky glycocalyx sugar coated serves as a protective layer that holds cell together cell recognition every cell has a unique carbohydrate in glycocalyxCell Junctions only certain types of cells can move freely in bloodstream blood cells sperm cells certain cancer cells cells bounded together by three factors adhesive glycoproteins in glycocalyx fit between adjacent membranes or special cell junctionsTight Junctions junctional protein chains hold cells together prevent passage of ions and molecules in the space between adjacent cells extracellularsometimes leaky allows small ions to pass throughoccurs in cells of GI tract to keep digestive enzymes out of blood Desosomes anchoring junctions along sides of cell to prevent separation linker proteins cahedrins attach to plaques inside the cell zip the adjacent cells up keratin filaments attach to plaque inside the cell and anchor to opposite wallGap Junctions communicating junctions between adjacent cells adjacent cells connected by channels connexions hollow tubes made up of transmembrane proteins channels allow passage of small ions sodium potassium ex heart muscles cells communicate electrically Membrane Transport cells are surrounded by extracellular fluid interstitial which contains a large mix of substances ions molecules glucose hormones neurotransmitters waste cells extract precisely what they need from this fluid and ejects what it doesnt need into the fluidPassive Transport No energy required simple diffusionfacilitated diffusionosmosisfiltration Diffusion the random mixing of molecules or ions due to their kinetic energy and constant motion a substance diffuses down a concentration gradient until it reaches equilibriumfactors affecting diffusion 1temperature directly related2concentration gradient directly related3molecular size inversely proportional4mass inversely proportional5distance inversely proportional Simple Diffusion passive diffusion directly through lipid bilayer nonpolarlipidsoluble molecules oxygencarbon dioxide will enter the cell through passive diffusion if there is a high concentration of oxygencarbon dioxide in the blood rate of diffusion is not controllableCarrierMediated Facilitated Diffusion passive diffusion via transmembrane carrier protein
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