Models of Passive Membrane

Abstract

From the point of view of irreversible thermodynamics, one of the most widely used models of passive membrane is the Nernst-Planck equation, which simply combines Ohm’s law for the flow of charged particles in an electrical-potential gradient and Fick’s first law for the diffusion of particles in a concentration gradient. In writing the Nernst-Planck equation, it is customary to deal with flow densities, i.e., the number of particles flowing through a unit of area in a unit of time. This quantity, usually labeled J, is particularly useful for membranes since one often is interested in the flow of particles through a given area of membrane.