BIOL 2213 Study Guide - Midterm Guide: Electrochemical Gradient, Lipid Bilayer, Facilitated Diffusion
29 Aug 2016
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The net movement of molecules/solutes from an area of high concentration to an area of low concentration o o. Understand the factors that affect diffusion through a lipid bilayer. Size, polarity, charge: polar substances and ions cannot pass through. Non-polar substances (carbon dioxide, oxygen, lipids and steroids) can. Small molecules pass through bilayer easier; large do not. Membrane potential: a separation of electrical charge exists across plasma membranes of all cells measured by charge resting is -70 mv. Provides an electrical force that influences the movement of ions across the membrane. The inside of a cell has a net negative charge with respect to the outside, there will be an electrical force attracting positive ions into the cell and repelling negative ions. The direction and magnitude of ion fluxes across membranes depend on both the concentration difference and the electrical different (the membrane potential).
