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PCB 3703C 4A- Interactions between cells and the extracellular environment Anh Bui.docx

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Body FluidsIn most individuals, approximately 67% of the total weight is water within cells,in the intracellular compartment.The remaining 33% of the total body water comprises the extracellularcompartment (outside of cell, blood vessel and interstitial space that connectscells to blood vessels.)About 20% of this extracellular fluid is contained in the vessels of thecardiovascular system, where it comprises the fluid portion of the blood, or bloodplasma.Role of the bloodTransports oxygen from the longs to the body cells, and CO2 from the body to thelungsTransports nutrients derived from food in the intestine to the body cellsOther nutrients between organs such as glucose from the liver to the brain, orlactic acid from muscles to the liver.Metabolic wastes from the body cells to the liver and kidneys for elimination inthe bile and urine, and regulatory molecules called hormones from endocrineglands to the cells of their target organs.Extracellular MatrixThe extracellular environment fluids, as interstitial, or tissue, fluid, within amatrix of glycoproteins and proteoglycans. It consists of the protein fiberscollagen and elastin. This fluid, derived from the blood plasma, provides nutrientsand regulatory molecules to the cells. The extracellular environment is supportedby collagen and elastin protein fibers, which also form the basal lamina belowepithelial membranes.IntegrinsAre a class of glycoproteins that extend from the cytoskeleton within a cellCategories of transport across the plasma membraneThe mechanisms involved in the transport of molecules and ions through the cellmembrane may be divided into two categories:1. Transport that requires the action of specific carrier proteins in themembrane, called carrier-mediated transport, carrier-mediated transportmay be further subdivided intoA. Facilitated diffusionB. Active Transport2. Transport through the membrane that is not carrier mediated. It involvesthe simple diffusion of ions, lipid-soluble molecules, and water throughthe membrane, Osmosis is the net diffusion of solvent (Water) through amembrane.Membrane transport processes may also be categorized by their energyrequirements:
Passive transport:is net movement of molecules and ions acrossmembranes from higher to lower concentration, it does not requiremetabolic energy. Passive transport includes simple diffusion,osmosis, and facilitated diffusion. (no ATP)Active transport:Net movement across a membrane that occursagainst a concentration gradient (low to higher region of higherconcentration). Active transport requires metabolic energy (ATP)and involves specific carrier proteins.

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Term
Spring
Professor
MORGAN

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