The Nernst equilibrium potential for an ion that is 10 times more concentrated in the cytosol compared to the extracellular fluid is about -60 mV. How much would the potential be if the extracellular concentration decreases 100-fold with no change in the intracellular concentration?

Question

Quizplus · Accepted Answer

According to the Nernst equation, V = (RT/zF) × ln(Cₒ/Cᵢ). We do not need to numerically evaluate this equation for the purpose of this question. If the potential was -60 mV when the concentration ratio was 0.1 (which means the ion is positively charged), now that the ratio is 0.001, the potential should be -180 mV, i.e. V = -60 mV × [ln(0.001)/ln(0.1)].

The Nernst Equilibrium Potential for an Ion That Is 10