Membrane potential
type of physical quantity
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 of kinetic energy and production of radiation must be taken into account.
Typical values of membrane potential is normally given in units of millivolts and denoted as mV. In many animal cells, Vm is typically in the order of tens of millivolts. It commonly falls in the range of about −20 mV to −200 mV depending on the cell type and state. For such typical negative membrane potentials, positive work is required to move a positive charge from the interior to the exterior. However, thermal kinetic energy allows ions to overcome the potential difference. For a selectively permeable membrane, this permits a net flow against the gradient.
Although the entire cell is considered negative inside, the fluids in the cell are electrically neutral.
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This entry incorporates text from “Membrane potential” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.