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Natural Science Forum / Biology / Microbiology / October 2005Neuron membrane charge density?
Hi All! I am looking for the *amount* of charge on the cell membrane of a neuron that leads to its resting potential. Ideally it would be nice to also know how much of this charge is K+, Na+, Cl- and whatever other ions may be significant. I would appreciate any literature refs or author names that you might have on this. Rudolf > I am looking for the *amount* of charge on the cell membrane of a neuron > that leads to its resting potential. Ideally it would be nice to also know > how much of this charge is K+, Na+, Cl- and whatever other ions may be > significant. I would appreciate any literature refs or author names that you > might have on this. You can estimate this from the voltage and membrane thickness. I think the resting potential is about 70 mV. The membrane is typically 10 nm. The capacitance per unit area will be 8.85 x 10**-12 Farad/meter x K / thickness. With a relative permittivity (K) of around 9 (estimate) this gives an approximate capacitance of .008 Farad/square meter. With a voltage of 0.07 volts across it, this capacitor will have a charge Q = CV coulombs, or Q = .008 * 0.07 = .0006 coulombs/square meter. This is approximately Q/1.6e-19 charges, or 3.5e15 charges/square meter. Converting to more useful units, this is 3500 charges/square micron of cell surface, or .0035 charges/square nanometer. You can't distinguish the charged species without knowing concentrations of ions. Duh ... me stupid ;) Thanks for laying it out like this and even doing the math. Rudolf In sci.bio Tom Knight <tk@mit.edu> wrote: >> I am looking for the *amount* of charge on the cell membrane of a neuron >> that leads to its resting potential. Ideally it would be nice to also know [quoted text clipped - 14 lines] > nanometer. You can't distinguish the charged species without knowing > concentrations of ions. |
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