Final answer:
Changing [K]in to 150mM can affect the equilibrium potential E_k, which is calculated using the Nernst equation. However, if the change in concentration is small, the initial concentration may be assumed to remain approximately the same, and thus the impact on E_k might be negligible.
Step-by-step explanation:
If the concentration of [K]in is changed to 150mM, the electrochemical equilibrium potential for potassium (Ek) is affected according to the Nernst equation. The Nernst equation, which calculates the equilibrium potential for an ion across a membrane, is sensitive to changes in ion concentrations on either side of that membrane. When dealing with equilibrium constants and reactions, if the concentration change is small compared to the initial concentration (change in concentration), it can be assumed that the initial concentration does not change significantly. For instance, if 'x' represents a small change and we consider 'x' to be much less than 150mM, the equation simplifies, reflecting that 150mM - x is approximately equal to 150mM. Therefore, in the calculation of Ek, the change may not substantially alter the predicted equilibrium potential if 'x' is sufficiently small.