Contents

1. Introduction

2. Sources of Experimental Data

3. Calculation of Standard Thermodynamic Properties of Species from Apparent Equilibrium Constants and Heats of Biochemical Reactions

4. Calculation of Standard Transformed Thermodynamic Properties of Reactants and Reactions at Specified pH

5. Further Transformed Thermodynamic Properties

6. Maxwell Relations

7. Use of Mathematica®

8. Statistical Mechanics of Systems of Biochemical Reactions

9. Names of Enzymes

10. Acknowledgement

5. Further Transformed Thermodynamic Properties

The use of Legendre transforms can be taken a step further in treating systems of reactions like glycolysis at constant concentrations of coenzymes like ATP, ADP, NAD_ox, and NAD_red. In metabolism, coenzyme concentrations may be quite constant because they are consumed and produced by many reactions. In this case the further transformed Gibbs energy G’’ of the system is defined by the Legendre transform G’’ = G’ - ∑n_c(coenz_i)µ(coenz_i). The concept of a further transformed Gibbs energy is also useful in treating protein-ligand equilibria, like the binding of oxygen by hemoglobin, because the system can be studied at specified ligand concentrations. The oxygenation of hemoglobin, for example, can be treated by using the transformed Gibbs energy, but it is also useful to consider the thermodynamics of such a system at specified concentrations of molecular oxygen. In this case the further transformed Gibbs energy G’’ is defined by G’’ = G’ - n_c(O₂)µ(O₂). The maximum number of Legendre transforms must be one less than the number of components in the system because one component must remain.

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