Suitable energetic conditions for dynamic chemical complexity and the living state

Abstract

Any living organism can be considered as a component of a dissipative process coupling an irreversible consumption of energy to the growth, reproduction and evolution of living things. Close interactions between metabolism and reproduction are thus required, which means that metabolism has two main functions. The first one, which is the most easily perceptible, corresponds to the synthesis of the components of living beings that are not found in the environment (anabolism). The second one, which is usually associated with the former, is the dissipative process coupling the consumption of energy to self-organization and reproduction and introducing irreversibility in the process. Considering the origin of life, the formation of at least some of the building blocks constituting a living organism can be envisaged in a close to equilibrium situation under reducing conditions (for instance in hydrothermal vents). However, coupling irreversibly self-organization with the dissipation of an energy flux implies far from equilibrium conditions that are shown in this work to raise quantitative requirements on the height of kinetic barriers protecting metabolites from a spontaneous evolution into deactivated species through a quantitative relationship with the time scale of the progress of the overall process and the absolute temperature. The thermodynamic potential of physical sources of energy capable of feeding the emergence of this capacity can be inferred, which leads to the identification of photochemistry at the wavelength of visible light or processes capable of generating activated species by heating transiently a chemical environment above several thousand Kelvin as the only processes capable of fulfilling this requirement. © 2012 Pascal; licensee Chemistry Central Ltd.