Consider the inside and outside of a cell, where the 8-nanometer-thick cell membrane has a large number of open Na⁺ Ion channels. The major contributor to these ions is dissolved NaCl. Let's analyze a "toy model" of the cell's resting potential in which the Na⁺ ion channels are the only ion channels, they are permanently open, and NaCl is the only contributor of Na⁺ions. Assume the outside of the cell has a concentration of 150 mM NaCl and that the concentration inside the cell is much, muchlower.

In this problem, use a temperature of 290K, at which k_BT = 0.025 K.

Part AIf the Nernst potential for the sodium ions in our toy model is 60 mV, what would the concentration of NaCl be on the inside of the cell? [ignore the Cl ions

Part BNow let us refine our model by noting that there is a second source of Na+ ions in the cell: NaI. Suppose the outside of the cell has a concentration of NaI of 0.04 mM and the inside has a NaI concentration of 4 mM. How will the presence of these ions change the Na⁺ Nernst potential across the membrane? (Assume the NaI is fully ionized in solution.)