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principles of complementarity
biochemical activities of cells are dictated by subcellular structures of cells
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plasma membrane
seperates the interior of the cell from the exterior
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plasma membrane-basic features
thin later composed of a lipid bilater with embedded proteins
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phospholipid bilater
phospholipid is hydrophilic and polar and the two fatty acid tails are hydrophobic and nonpolar
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integral proteins
proteins firmly inserted in the lipid layer, some form clusters or channels for small water-soluble molecules or ions to move through the lipid bilayer and other function as carrier proteins
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peripheral proteins
loosely attatched, some are supportive filaments and some are enzymes
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glycocalyx
carbohydrate coating on the outer surface of the cell membrane, provides highly specific biological markers
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cholesterol plates
stabalize the cell membrane
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microvilli
minute fingerlike extensions of the plasma membrane that increase the absorptive surface area
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tight junctions
protein molecules in adjacent plasma membranes forming an impermeable junction, precent molecules from passing throught the extravellular space (GI tract)
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desmosomes
anchoring junctions, also contribute to a continuous internal network suport (skin, heart muscle)
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gap junctions
allow chemicals to pass between adjacent cells, ions, sugars and other small molecules can pass through
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interstitial fluid
cells sit in the extracellular fluid
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passive properties
substances go through the membrane without using energy
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diffusion
molecules move from high concentration to low concentration
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simple diffusion
substances that are nonpolar and lipid soluble including oxygen and carbon dioxide can go through the lipid membrane, small polar and charged particles can diffuse through the water filled protein
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facilitated diffusion
passive process, but requires binding to a protein carrier, molecules such as glucose are too large for the protein channels and too polar for the lipid bilayer, change in structure of the carrier protein as it moves glucose across the membrane, transport limited by the number of carriers
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osmosis
the diffusion of a solvent such as water across the cell membrane
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osmotic pressure
the pull on water by solute concentration
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hydrostatic pressure
pushing water across the membrane,filtration
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isotonic
the same concentration of solutes as a cell
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hypotonic
solutions more dilute than cells
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hypertonic
solutions more concentrated than cells
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filtration
to force water and other solutes across a membrane by fluidor hydrostatic pressure
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active processes
the cell provides energy to moce substances through the membrane
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active transport
requires a carrier that is specific, and because it transports against the concentration gradient, requires energy
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primary active transport
hydrolysis of ATP results in phosphorylation of the transport protein, which changes shape and pumps the solute across the membrane
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sodium-potassium pump
drives sodium out and potassium into the cell
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secondary active transport
pump the maintains sodium gradient, that can secondarily transports another solute
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