Gnaiger 1990 Thermochim Acta
|Gnaiger E (1990) Concepts on efficiency in biological calorimetry and metabolic flux control. Thermochim Acta 172:31-52.|
Abstract: Accurate definitions of efficiency are required to resolve controversies on the significance and comparability of measures of efficiency in biological energetics. This review on concepts of efficiency is arranged into 4 parts. First, some fundamental energy relations of equilibrium and nonequilibrium thermodynamics are defined and placed into a coherent context as relevant for efficiency in biology. The classical expression of the Carnot efficiency of a heat engine obtains a new meaning in terms of flux-force relations of nonequilibrium thermodynamics. Second, within this general thermodynamic frame, the specific treatment of energy transformations of chemical reactions is introduced, with particular emphasis on open systems with internal transformation and external transfer of matter. Third, the chemical transformations in ATP turnover and internal efficiencies of coupled reactions are analyzed in two parts. On the one hand, the enthalpy efficiency is relevant in the context of biological calorimetry in relation to uncoupling and the integration of aerobic and anaerobic metabolism. On the other hand, the molar Gibbs energy efficiency relates to the driving force of coupled reactions and to the control of flux. High metabolic power and maximum efficiency are mutually exclusive. Finally, the discussion of various expressions of efficiency in biological growth requires a careful distinction between energy conservation in transformations (chemical reactions) and energy acquisition in coupled transformation and transfer of energy in the form of externally supplied matter. Better understanding and management of biological resource utilization requires this combined analysis of efficiency in biological energetics.
Labels: MiParea: Respiration
Regulation: Aerobic glycolysis, Coupling efficiency;uncoupling, Flux control