BIOC 4580 Study Guide - Midterm Guide: Lipid Bilayer, Valinomycin, Faraday Constant
6 Mar 2017
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Class 13: transport processes overview + diffusion and facilitated diffusion. Rate is governed by the concentration difference (c1-c2) Charged solutes accounting for concentration and ionic equilibrium: = (cid:373)e(cid:373)(cid:271)ra(cid:374)e pote(cid:374)tial (cid:894)v(cid:895) = (cid:894) i(cid:374) out(cid:895) z = unit charge (+1/-1, +2/-2, etc. ) Transport of +vely-charged solute from +vely-polarized side to (cid:448)el(cid:455)-polarized side release of free energy (versus uncharged solute) i. e. , zf is a (cid:374)egati(cid:448)e ter(cid:373: membrane potential: -60 mv negative inside. E. g. indole, nonpolar gases (d > 10-4 cm2/s) e. g. glucose, urea, glycerol (d = 10-8- 10-6 cm2/s) Remove charge higher rates of transport, but still small. Low lipid diffusion high energy barrier to overcome. Charged and polar molecules must shed their hydration sphere before passing through gaps in lipids energetically unfavourable. Strip off the water molecules solute can move across barriers quickly. Size, polarity, and charge govern rates of diffusion across lipid bilayers. Charged and polar molecules must shed their hydration sphere before passing through gaps between lipids.
