Membrane Potential vs. Equilibrium Potential: Key Differences Explained
Membrane Potential is the voltage across a living cell’s membrane at any moment; Equilibrium Potential is the theoretical voltage when one ion type is perfectly balanced—no net flow.
People swap the terms because both involve ions and millivolts. Think of Membrane Potential as your phone’s live battery level, while Equilibrium Potential is the 100 % mark for just one app.
Key Differences
Membrane Potential results from many ions and pumps; Equilibrium Potential is a single-ion calculation. The first is measured; the second is computed.
Which One Should You Choose?
Use Membrane Potential to describe real cell behavior; cite Equilibrium Potential when explaining why potassium efflux alone stabilizes at –90 mV.
Examples and Daily Life
A neuron firing at –70 mV shows Membrane Potential; its potassium Equilibrium Potential of –90 mV explains why repolarization rushes toward that number.
Can a cell’s Membrane Potential equal its Equilibrium Potential?
Rarely—only if all other ion channels close and one ion dominates.
Is Equilibrium Potential always more negative?
No, sodium’s can be +60 mV, far above resting membrane levels.