The long term objective is to increase the usefulness of equilibriumcalculations on biochemical reactions. Thermodynamics determine whether a reaction goes in the forward or reverse direction and whether it will absorb or evolve heat. More specifically, thermodynamics makes it possible to calculate equilibrium compositions and heat evolutions using data that often comes from other reactions. Knowledge of the thermodynamics of a reaction and knowledge of the kinetics of the forward reaction make it possible to calculate the kinetics of the reverse action. Chemical equilibrium in biological systems is complicated by the fact that apparent equilibrium constants depend on pH and pMg, as well as on temperature, pressure and ionic strength. A better understanding of these effects will facilitate the interpretation of metabolism and problems that are encountered in certain diseases. Thermodynamic information on biochemical reactions is currently stored as equilibrium constants and heats of specific reactions. These data can be interpreted by the use of recently developed techniques to obtain thermodynamic properties of individual reactants, which can then be used to calculate equilibrium constants and heats of reactions that have not even been studied previously. One objective of this project is to prepare thermodynamic tables on the properties of reactants so as to increase the usefulness of current knowledge. Another objective is to use new concepts in biochemical thermodynamics to investigate coupling of reactions by enzymes, missing reactions in systems like glycolysis, muscle, and chemosmotic theory.