Final answer:
Changing the external potassium concentration [K]out to 150mM would typically increase the equilibrium potential for potassium (E k), subject to the logarithmic nature of the Nernst equation, which might result in a less pronounced change if the increase is minor relative to total concentration.
Step-by-step explanation:
When the external potassium concentration [K]out is changed to 150mM, the Nernst equation is used to determine the effect on the equilibrium potential for potassium (Ek). The Nernst equation involves taking the ratio of the external and internal ion concentrations to calculate the potential. Considering that the change in concentration does not significantly alter the initial concentration because it is small compared to the equilibrium constant K, we can approximate that the initial concentration remains fairly constant.
In this case, if the external concentration [K]out is raised, it would generally result in an increase in the Ek, depolarizing the membrane potential if all other factors remain constant. However, if this increase is minor compared to the total concentration, the change in Ek might not be pronounced due to the logarithmic nature of the Nernst equation.