Answer Happy

2) You have constructed a model system to study ionic permeability. You have allowed a lipid bilayer to form across a small hole in a plastic barrier separating two solution-filled compartments. Spanning this lipid bilayer are two channel populations, one a population of channels solely permeable to potassium ions (K+), and the other a population of channels solely permeable to sodium ions (Na+). The conductance of a single K+ channel is determined to be 12 pS. The conductance of a single Na+ channel is 4 pS. The membrane has many ion channels in it. The ionic concentrations in the right and left compartments are: [K+]R 10 MM; [K+] = 400 mM [Na+]R = 460 MM; [Na+] = 50 mM Using a voltmeter, you determine that the left compartment is 65 mV more negative than the right compartment. a. What is the relative conductance of this membrane for sodium and potassium? Hint: For a stable resting potential, the leftward and rightward currents must be equal, so using Ohm's law as we discussed in class gk* (Vm - Ek) = 9Na * (Vm - Ena) b. Given the conductances of individual channels given above, what is the ratio of channel types in this system? Hint: total conductance reflects both number of channels & conductance of each channel. c. If you were to inject positive charge into the right compartment so it was 50 mV more positive than the left compartment, in which direction would the net flow of each ion be?