In membrane
biophysics sometimes used interchangeably with
cell potential, but applicable to any
lipid bilayer or
membrane. Hence every
organelle and every membranous compartment (such as a synthetic
vesicle) has a transmembrane potential (although the size of this potential may be zero). The
transmembrane potential is the voltage "drop" or the difference in voltage between one face of a bilayer and its immediate opposite face. The property need not be uniform throughout the cell or compartment, but under some conditions may vary between one patch of membrane and another. At any moment during the
action potential of a
nerve cell, for example, the magnitude of the transmembrane potential will vary along the
axon; and at any single point on an axon that is conducting an action potential, likewise, the transmembrane potential will vary with time. Strictly, it is the transmembrane potential or transmembrane electric field, and not the cell potential that controls the transmembrane flow of charged solutes and the activity of voltage-gated
ion channels.
- Compare electrochemical potential