Chapter 11 - Thermodynamics and Biological Systems

Abstract

This chapter presents a simplified analysis of biological processes including mitochondria and energy transduction. Systems may exhibit a tendency towards maximum disorder or the spontaneous appearance of a high degree of organization in space, time, and/or function. The best examples of this behavior are dissipative systems at nonequilibrium conditions, such as Bénard cells, and living systems. The distinctive characteristics of living systems include diversity and adaptation, complexity, homochiral character, dynamic character, and far-from-equilibrium state. Organized structures require several coupled metabolic reactions and transport processes that control the rate and timing of life processes. Biochemical reaction cyclic processes maintain the biological cell in nonequilibrium state by controlling the influx of reactants and efflux of products. Biological systems do not decay towards an equilibrium state, but instead increase in size, developing organized structures and complexity. An evolved and adapted biological system converts energy in an efficient manner for the transport of substances across a cell membrane, the synthesis and assembly of proteins, muscular contraction, reproduction, and survival. The source of energy is adenosine triphosphate, which is produced by oxidative phosphorylation in the inner membrane of the mitochondria. Kinetic equations and statistical models can describe such processes satisfactorily. However, these procedures often require detailed information, which may be unavailable. The nonequilibrium thermodynamics theory may be a useful approach to a describe energy pathways and coupling in a quantitative manner, evaluate the stoichiometry in partially coupled systems, and formulate the efficiency of energy conversion in bioenergetics.