Week #2: Transport through Cells
Week #2: Transport through Cells BIO 183
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This 3 page Class Notes was uploaded by Anna Huryn on Friday January 8, 2016. The Class Notes belongs to BIO 183 at North Carolina State University taught by Dr. Miriam Ferzli in Fall 2015. Since its upload, it has received 30 views. For similar materials see Intro to Bio Cell/ Micro in Biological Sciences at North Carolina State University.
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Date Created: 01/08/16
Anna Huryn Week #2: BIO 183 Dr. Miriam Ferzli Transport through Cells There are two types of transport: active and passive; active transport expends energy to move materials while passive does not Passive Transport: Diffusion = spontaneous movement of ions or molecules along a concentration gradient; from an area of high concentration to an area of low concentration Osmosis = diffusion of water through semi-permeable membrane Facilitated diffusion = passive diffusion aided by channel or carrier proteins *channel proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane *aquaporins are for water *carrier proteins bind to molecules and change shape to shuttle them across the membrane Active Transport: Uses energy to pump ions or molecules against their concentration gradient which is performed by specific proteins embedded in the membranes Energy is provided by ATP which supplies it by transferring a phosphate group from ATP (forming ADP) to the transport protein ex. Sodium-potassium pump, which maintains the membrane potential (over-all charge of the cell) The Electrochemical Gradient: Two combined forces, collectively called the electrochemical gradient, drive the diffusion of ions across a membrane The voltage across a membrane is called the membrane potential o The inside of a cell is negative while the extracellular fluid is positive o The membrane potential favors the passive transport of cations into the cell and anions out of the cell Anna Huryn Week #2: BIO 183 Dr. Miriam Ferzli Electrogenic Pumps • Electrogenic pumps generate the voltage gradient across a membrane • sodium-potassium pump is the major electrogenic pump of animal cells. • proton pump is the major electrogenic pump in plants, bacteria, and fungi • ATP-powered pump that transports one solute can indirectly drive the active transport of Anna Huryn Week #2: BIO 183 Dr. Miriam Ferzli several other solutes in a mechanism called secondary active transport Bulk Transport: Exocytosis = secretion of cellular contents to the outside of the cell by fusion of vesicles to the plasma membrane Endocytosis = uptake of extracellular material into the cell Ex. Phagocytosis, pynocytosis, receptor-mediated endocytosis
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