Aspects physiques de l'autocatalyse

At the heart of cellular metabolism lies its ability to reproduce essential biomolecules from pre-existing ones. In the case of chemical systems, this property is called autocatalysis, and can be defined as the fact that a set of species can sustain itself through a set of reactions. Discovered in the second half of the 19th century for inorganic reactions, autocatalysis remained unexplored for a long time. However, the emergence of research into the appearance of life on Earth, in which autocatalysis is a central concept, and the understanding of present-day metabolism have led to growing interest in the subject. Nevertheless, the theoretical description of autocatalytic systems is still incomplete. Such a description must imperatively take into account the physical and chemical constraints specific to such systems. In this respect, recent work has established the topological constraints to which autocatalytic networks must conform, unifying previous approaches within a common framework, and enabling a classification of such systems to be established. Nevertheless, how this topology shapes the dynamics of autocatalytic systems remains elusive. The aim of this work is therefore to investigate the consequences of this particular topology on the behavior of autocatalytic networks, particularly when they are operating far from equilibrium, as is the case within metabolism. In particular, as this classification of autocatalytic networks is based solely on topology, and not kinetics, it only authorizes species production a priori. It is therefore necessary to highlight the fact that the latter does indeed imply the existence of productive processes within autocatalytic systems. On the other hand, a chemical system will spontaneously tend to oppose species production by seeking to reach a state of equilibrium. As a result, the latter must be maintained via external processes, and will therefore not be energy-neutral. It is therefore necessary to identify the thermodynamic cost that an operator must exert to maintain productive processes in a non-equilibrium network.