A thermodynamic description for physiological transmembrane transport

Physiological mechanisms for passive and active transmembrane transport have been theoretically described using many different approaches. A generic formulation for both passive and active transmembrane transport, is derived from basic thermodynamical principles taking into account macroscopic forward and backward molecular fluxes, relative to a source compartment, respectively. Electrogenic fluxes also depend on the transmembrane potential and can be readily converted into currents. Interestingly, the conductance-based formulation for current is the linear approximation of the generic formulation for current, around the reversal potential. Also, other known formulas for current based on electrodiffusion turn out to be particular examples of the generic formulation. The applicability of the generic formulations is illustrated with models of transmembrane potential dynamics for cardiocytes and neurons. The generic formulations presented here provide a common ground for the biophysical study of physiological phenomena that depend on transmembrane transport.