Ohm\'s law states V = I R, Instead of resistance, one can express this in terms

Question

Ohm's law states V = I R, Instead of resistance, one can express this in terms of conductance g. V = I/g or I = V g. The measured value of "conductance per unit area" of sodium channels is 0.13 ohm^-1 m^-2 in the resting state of giant axons. The concentration of sodium inside the cell is 12mM while outside the cell is 145mM; the membrane voltage is -90 mV. If pumps are suddenly turned off, sodium will rush in. Find the current per unit area carried by sodium ions. Re-express your answer as current per unit length along the giant axon assuming a diameter of 1 mm. Make a rough estimate of how long it will take for the internal concentration of sodium to match that of the outside. Assume current is constant through the whole time for this estimate. Action potential lasts for about a few millisecs. Assume that during the action potential sodium's conductance rises transiently to 100 ohm^-1 m^-2. Comment on how the time calculated in c compares with the time that action potential lasts for. Give an example of importance of bioelectricity/charges in any process except action potential generation and propagation. Express k_B T(4.1 times 10^-21 J) in eV and pN-nm. Charge of an electron = 1.6 times 10^-19 C. How will approximate time taken to diffuse and find another protein depend on the concentration of that protein - assume a protein with diffusion constant D = 50 mu m^2/sec. Estimate distance between H^+ ions particles at pH 4. Roughly estimate how many H^+ ions would be present in a typical lysosome (guess a radius).

Explanation / Answer

1 a) Given: conductance g = 0.13 ohm-1m-2

Voltage V = -90 mV

I = Vg = 90 * 0.13 = 11.7 mA

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