Question

Imagine another cell with a more typical K+ concentration gradient: [K+]o = 4.5 mM and [K+]i = 140 mM. The Nernst equation calculates EK = -92 mV. Given the previous info, what is this cell's membrane potential if it is only due to K+ ions?

Answer 1

If a cell's membrane potential is determined solely by K+ ions, with [K+]o = 4.5 mM and [K+]i = 140 mM, and EK = -92 mV, then the membrane potential would be -92 mV. This is different from the typical resting membrane potential, which is commonly around -70 mV due to contributions from other ions and the Na+/K+ pump.

Step-by-step explanation:

The membrane potential of a cell with a typical K+ concentration gradient, where [K+]o = 4.5 mM (outside concentration) and [K+]i = 140 mM (inside concentration), is determined by the Nernst equation. When EK = -92 mV as calculated by the Nernst equation, and if the membrane potential is solely due to K+ ions, the membrane potential of this cell would also be -92 mV.

At rest, K+ ions tend to leave the cell through channels that are open much of the time, which contributes to a negative charge inside the cell. Conversely, Na+ channels are rarely open, maintaining the high concentration of Na+ outside. The process of repolarization brings the membrane potential back towards the resting potential after any disturbance, such as during the phases of an action potential.