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Unformatted text preview: Lecture Notes Bio 109, Fall 2010, Dr. Catherine Loudon Lecture 3 09/29/10 Osmolarity, membrane potential, Nernst equation 1) Announcements a) Change in office hours: now 9-10 am on Tuesdays (changed time for conference room availability near office) b) Bio Sci tutoring starts next week 2) Rate of diffusion described by Ficks law (continued) a) Note that concentration gradient is concentration difference/thickness [in contrast to books use of concentration gradient as synonym for concentration difference which is not correct] (difference means subtract one from another) b) Thickness can also be thought of as distance between the two points or areas where two concentrations are measured (the two concentrations used to calculate concentration difference) 3) Diffusion across membranes a) Membrane must be permeable to particular chemical species i) Permeability can be modified by proteins in membrane ii) Lipophilic vs. lipophobic compounds b) Membranes are lipid bilayers with many inserted proteins (Fig. 5-6) (also see Fig. 3-6, Membranes are lipid bilayers with many inserted proteins (Fig....
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- Spring '10