Thermodynamics of Concentration vs Flux Control in Chemical Reaction Networks

TL;DR

This paper explores the thermodynamic relationship between concentration and flux control mechanisms in open chemical reaction networks, demonstrating their equivalence at steady state and differences in growth regimes.

Contribution

It shows that concentration and flux control mechanisms can be mapped onto each other thermodynamically, extending existing theories to flux control.

Findings

Thermodynamic potentials are similar for both control mechanisms.

The two mechanisms are equivalent at steady state.

Flux control can lead to different growth regimes.

Abstract

We investigate the thermodynamic implications of two control mechanisms of open chemical reaction networks. The first controls the concentrations of the species that are exchanged with the surroundings, while the other controls the exchange fluxes. We show that the two mechanisms can be mapped one into the other and that the thermodynamic theories usually developed in the framework of concentration control can be applied to flux control as well. This implies that the thermodynamic potential and the fundamental forces driving chemical reaction networks out of equilibrium can be identified in the same way for both mechanisms. By analyzing the dynamics and thermodynamics of a simple enzymatic model we also show that, while the two mechanisms are equivalent at steady state, the flux control may lead to fundamentally different regimes where systems achieve stationary growth.