Page 179 - Thermodynamics of Biochemical Reactions

Thernwdyanamics of Biochemical Reactions. Robert A. Alberty
Copyright 0 2003 John Wiley & Sons, Inc.
ISBN 0-471-22851-6

,i+ 11.1 Introduction to Semigrand Partition Functions
5 11.2 Transformed Gibbs Energy for a System
Containing a Weak Acid and Its Basic form at a
Specified pH
W 11.3 Semigrand Partition Function for a System
Containing Two Pseudoimsomer Groups at a
Specified pH
2; 11.4 Semigrand Partition Function for a Biochemical
Reaction System at Specified Concentrations
of Coenzymes
+ 11.5 Discussion

The introduction of transformed thermodynamic properties to biochemical ther-
modynamics owes a lot to statistical mechanics because these calculations follow
the pattern of calculations on reaction equilibria in systems of gaseous hydrocar-
bons at specified partial pressures of molecular hydrogen, ethylene, or acetylene.
Alberty and Oppenheim (1989) used a semigrand partition function to describe
the equilibrium distribution of alkyl benzenes at elevated temperatures as a
function of the partial pressure of ethylene. The transformed Gibbs energy G‘ of
a system at a specified pH can be calculated using a semigrand partition function
(Alberty, 2001~). The further transformed Gibbs energy G” of a system of
biochemical reactions can be calculated using a semigrand partition function with
the steady state concentrations of coenzymes as intensive variables (Alberty,
2001g, 2002a).
Statistical mechanics provides a bridge between the properties of atoms and
molecules (microscopic view) and the thermodynmamic properties of bulk matter
(macroscopic view). For example, the thermodynamic properties of ideal gases
can be calculated from the atomic masses and vibrational frequencies, bond
distances, and the like, of molecules. This is, in general, not possible for
biochemical species in aqueous solution because these systems are very compli-
cated from a molecular point of view. Nevertheless, statistical mechanmics does
consider thermodynamic systems from a very broad point of view, that is, from
the point of view of partition functions. A partition function contains all the
thermodynamic information on a system. There is a different partition function
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