BIOL-4610 Lecture Notes - Lecture 2: Lipid Bilayer, Partition Coefficient, Chemical Polarity
10 Sep 2018
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Aquaporins: allow water and glycerol to enter the cell. They move through the center of each subunit. Erythrocyte plasma membrane provides examples of transport mechanisms. K+ ions move inward and na+ ions move outward. Channels = allow h2o and ions to enter cell rapidly. Simple diffusion: direct unaided movement of solute molecules into and through lipid bilayer. Rate increases as the concentration difference inside and outside the cell increases. Involve gas and small uncharged water soluble molecules. Rate and direction: rely on concentration gradient, size of ion, hydrophobicity (polarity) and membrane potential. Most molecules cant diffuse at rate for cell needs. Nonpolar molecules dissolve more readily in hydrophobic conditions. Diethylurea k= 0. 01 <= 50x more hydrophobic than urea. Concentration gradient: movement of molecules from area of high concentration to area of low concentration. Magnitude of the different in concentration of a substance on the opposite side of the membrane.
