Final answer:
Changing the external potassium concentration to 150mM will affect the potassium equilibrium potential (EK), making it less negative as described by the Nernst equation, assuming the internal potassium concentration remains constant.
Step-by-step explanation:
If the external potassium [K]out concentration is changed to 150mM, the potassium equilibrium potential (EK) will be affected. This is because the value of EK is dependent on the ratio of the external to internal potassium concentrations, as described by the Nernst equation.
All else being equal, increasing the external potassium concentration without a corresponding change in the internal concentration will cause the potassium equilibrium potential to become less negative (i.e., closer to zero), meaning that potassium ions would have less tendency to move into the cell according to their electrochemical gradient.
Typically, this kind of analysis would involve solving the Nernst equation given the new potassium concentration, assuming the internal concentration remains constant, which allows us to understand the directional change of EK.