Origin of Electrical Potentials

Abstract

The various kinds of electrical potential that are connected with biological membranes can be divided in various ways. For instance, according to their location we may distinguish between “transmembrane” potentials and “membrane surface” potentials. The former are due to an electric field which penetrates the whole membrane phase and can, therefore, be detected between the two adjacent bulk solutions by the usual electrodes. The latter cannot easily be so detected as they are located at the boundary between the membrane phase and the adjacent bulk solution. One can also divide the potentials from an energetic point of view, namely into “equilibrium” potentials and “nonequilibrium” potentials. The former belong the systems which have reached complete equilibrium or are restained from doing so and cannot therefore serve as a source of free energy, whereas the latter tend to change toward equilibrium, thereby making (under suitable conditions) free energy available.