ABSTRACT
This final chapter examines the question of why there are upper and lower limits for irreversible entropy increase by living systems. We also discuss here how likely it is that biological evolution maximized produced power or minimized entropy generation. The acquired and released (dissipated) energy from living systems contains the signatures of potentially useful work and power. Life is not a passive dissipation-producing process. It regulates the cycles of dimensional contraction and expansion, transforms input power into dissipation, adapts to higher or lower external forcing, and steers its far-from-equilibrium patterns toward dissipative self-organization. In animal and plant cells, the respiratory control of mitochondrial bioenergetics is a good example of ubiquitous regulations that should not be neglected in attempts to define what is life. Dominant entropy-producing transitions are coupled to nonequilibrium conformational switches, rate-limiting steps, and signaling processes enabling the intelligent-like behavior of living cells. We conclude that dissecting entropy production of living cells and its macromolecules is not an exercise in futility. The life origin is revisited using the vehicle of the unique biosphere-mineralogy connection, the "birth canal" of biology idea, and recently perceived difference among biological and physical systems – only the former have an in-built ability to predict the future. The physical foundation for prebiotic and biological evolution is likely to be an appropriately modified last action principle. Recent advances in unifying different physics branches point toward ever more general extensions of thermodynamics in the realm of quantum thermodynamics, generalized least action principle, and the entropic principle for selecting the universe where we live. All of them have been connected to the maximum entropy production principle and are relevant in bioenergetics too. We recently observed that the evolution of enzymes with increased catalytic efficiency is coupled to the increased entropy production in the environment. In the language of entropy changes, life accelerates the spread of entropy increase in those parts of the universe where it exists. In that sense, bioenergetics of present-day cells and organisms bridges the life-universe boundary.
