Membrane Potential

∞ generated and posted on 2015.12.30 ∞

Voltage that exists going from outside to inside of an organelle or cell.

A Membrane Potential consists of an excess of charged particles on one side of a membrane versus the other; these charge excesses represent potential energy just as water found at the top of a waterfall represents potential energy.

A membrane potential is an electrochemical gradient-associated voltage that is found across a lipid bilayer. Membrane potentials in particular represent the "electro" portion of electrochemical gradients. Cell membranes here consist of lipid bilayers, so membrane potentials are electrical potentials (a.k.a., voltages) that are found across lipid bilayers, and these potentials are carried by charged particles.

The membrane potential itself exists as an electrical charge difference between the two sides of a membrane and thus across a membrane. For example, there can be an excess of protons (charged hydrogen ions) or other cations found on one side of a membrane versus the other.

Membrane potentials represent stored energy (i.e., 'potential energy') that can be tapped by allowing the charged particles making up the electrochemical gradient to move down their concentration gradient as well as towards the opposite charge found on the other side of the membrane.

That energy of movement, literally kinetic energy, can be tapped to do work such as pumping other substances against their concentration gradient or instead to generate ATP from ADP and inorganic phosphate.

See Proton pump, Electron transport chain, and Sodium-potassium pump, which are all responsible for generating electrochemical gradients across cell membranes and therefore generating membrane potentials. See also the concepts of resting potential and action potential.