Active transport: A kinetic description based on thermodynamic grounds

TL;DR

This paper introduces a thermodynamically grounded kinetic framework for biological active transport, extending nonequilibrium thermodynamics to nonlinear regimes and applying it to calcium transport by ATPase.

Contribution

It develops a local equilibrium mesoscale description that unifies thermodynamic and kinetic approaches for biological transport processes, including nonlinear effects.

Findings

Nonlinear kinetic equations derived from thermodynamics.

Transport of Ca$^{2+}$ depends on Gibbs energy non-linearly.

Framework applicable beyond linear response regimes.

Abstract

We show that active transport processes in biological systems can be understood through a local equilibrium description formulated at the mesoscale, the scale to describe stochastic processes. This new approach uses the method established by nonequilibrium thermodynamics to account for the irreversible processes occurring at this scale and provides nonlinear kinetic equations for the rates in terms of the driving forces. The results show that the application domain of nonequilibrium thermodynamics method to biological systems goes beyond the linear domain. A model for transport of Ca$^{2+}$ by the Ca$^{2+}$-ATPase, coupled to the hydrolysis of adenosine-triphosphate is analyzed in detail showing that it depends on the reaction Gibbs energy in a non-linear way. Our results unify thermodynamic and kinetic descriptions, thereby opening new perspectives in the study of different transport phenomena in biological systems.