Membrane potential

Electric potential difference between interior and exterior of a biological cell The electrical charge across a cell membrane resulting from different concentrations of ions on the inside of the cell vs. the outside of the cell. Key: Blue pentagons – sodium ions; Purple squares – potassium ions; Yellow circles – chloride ions; Orange rectangles – membrane-impermeable anions (these arise from a variety of sources including proteins). The large purple structure with an arrow represents a transmembrane potassium channel and the direction of net potassium movement. Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. By convention it is written as Vm=Vinside−Voutside, thus a negative membrane potential means the cell interior is negative relative to the outside.It equals the interior potential minus the exterior potential. This is the energy per charge which is required to move a very small positive charge at constant velocity across the cell membrane from the exterior to the interior. Note, though, that if the charge is allowed to change velocity, the change o