Final answer:
Doubling the external K+ concentration to 10 mM will make the resting membrane potential less negative due to the decrease in the concentration gradient of K+ across the cell membrane, as predicted by the Nernst and GHK equations.
Step-by-step explanation:
The question revolves around the Goldman-Hodgkin-Katz (GHK) equation and what happens to the resting membrane potential when the external concentration of potassium (K+) doubles. Normally, resting membrane potential is maintained by a balance of ions, in particular Na+ and K+, and the selectively permeable nature of the cell membrane, which is typically around -70 mV in a resting state.
Potassium ions (K+) play a key role in this balance, as they are the primary charge carriers that move through K+ channels that are more frequently open compared to Na+ channels.
When the external K+ concentration doubles to 10 mM, according to the Nernst equation, the equilibrium potential for K+ (EK) will increase, and thus the resting membrane potential will become less negative (closer to zero).
This happens because the resting membrane potential is dependent on the concentration gradients of ions across the membrane, with higher external K+ reducing the gradient. While the GHK equation takes into account multiple ions, in this simplified scenario, we primarily consider the change in K+ concentration resulting in a change in the membrane potential.