Energy transduction in biological systems: A mesoscopic non-equilibrium thermodynamics perspective

We review recent efforts aimed at analyzing energy transduction processes in biological systems from the perspective of mesoscopic non-equilibrium thermodynamics. The inherent nonlinear nature of many of these systems, which undergo activated processes, has over the years impeded the use of classical non-equilibrium thermodynamics for their description, because this theory accounts only for the linear regime of these processes. The difficulty of putting non-equilibrium thermodynamics methods into a broader scope has recently been overcome. It has been shown that if one assumes local equilibrium at short time and length scales, in the mesoscale domain, the limitation of only providing linear laws can be removed and Arrhenius type nonlinear laws can be derived. The new theory proposed here provides a scenario under which transformations taking place in chemical and biological processes can be studied. We show in this paper how the theory can be applied to describe energy conversion processes in molecular motors and pumps and conclude that both systems can be studied by means of this common framework.