energy (ATP) required to move solute across the membrane against concentration gradientenergy viahydrolysis of ATP (primary active transport)energy stored in an ionic concentration gradient (secondary active transport)solutes actively transported include: ions (ex. H, NA, K, Ca, I and Cl), amino acids, and monosaccharidesprimary active transportenergy from hydrolysis of ATP permits the changing of shape of carrier proteinscarrier proteins that mediate active transport often called pumps40% ATP committed to thisPumpMost prevalent primary active transport is for sodium ions (Na+) and potassium (K+)Sodium out and potassium in (sodium-potassium pump)Works non-stop as sodium and potassium constantly leaking in and outWorks viaBinding 3 NA in cytosolTriggers hydrolysis of ATP and attachment of phosphate ot carrierResults in change of shape which releases Na to extracellular fluidNew shape permits binding of two potassium ionsTriggers release of phosphate on carrier and subsequent change of shape which dumps potassium within cytosolNa+/K+ pump or Na+/K+ ATPaseEnzyme is called Na+/K+ATPasesecondary active transportenergy stored in sodium and hydrogen concentration gradients is used to drive other substances against their concentration gradientprimary transport keeps Na against its concentration gradient which stores potential energyleakage of Na back inside converts this energy into kinetic energy which can be used to transport materialCarrier proteins transport both Na ion and material simultaneouslySymporter if both traveling same directionEx. Glucose and amino acids inside cell Antiporter if they traveling opposite directionsEx. For Ca2+ and H+outside cytosolvesicular transportanother mechanism used for transport of material using tiny spherical membrane sacsincludes:endocytosis (materials move into cell via fusion with plasma membrane)
three types of endocytosis: receptor-mediated endocytosishighly selective type of endocytosis by which cells take up specific ligands (molecules that bind to specific receptors)vesicles only form when receptor protein recognizes particle in ECFex. Low density lipoproteins, trasnferrin, some vitamins, antibodies, and certain hormonesprocess involvesbindingon extracellular side, formation of receptor-particle complex occursvesicle formationinvagination of edges of membrane UncoatingLoss of clathrin coating to become uncoated vesicleFusion with endosomeFuses with endosome which separates particle from vesicleRecycling of receptors to plasma membraneReceptors go to elongated portion of endosomewhich pinch off and traveling to plasma membrane after 10 mins of entering cellDegradation of lysosomeLysosome digests the endosome formed vesicle housing the particles, thus releasing particles into cytosolPhagocytosis
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- Fall '15
- cell biology, Cytosol