Lecture+notes+04 - Copy

Lecture+notes+04 - Copy - Lecture Notes Bio 109, Fall 2010,...

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Lecture Notes Bio 109, Fall 2010, Dr. Catherine Loudon Lecture 4 – 10/01/10 – Feedback loops, control systems 1) Announcements a) Second copy of quiz 1 activated today i) Open for a full week ii) Optional – for students who don’t have book yet (bookstore ordering problems) b) iClicker will start counting on Monday (bookstore ordering problems) 2) Nernst equation continued a) At equilibrium, the tendency for ions to move down their concentration gradient will be exactly balanced by their tendency to move down their electrical gradient (can be represented by two arrows of equal length pointing in opposite directions) b) For Na+ example of last time (ENa+ = +61 mV), this means that if the membrane is suddenly made permeable to Na+, Na+ would rush into the cell until Vm = +61 mV c) Note that the concentration of the ions will not be affected very much because a very small number of ions moving across a membrane makes a huge difference in the Vm d) At equilibrium, if membrane permeable to that ion, there will be no net movement of that ion 3) Water movement, ions, and Nernst a) Consider case of two compartments separated by a barrier permeable to water only
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Lecture+notes+04 - Copy - Lecture Notes Bio 109, Fall 2010,...

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