Thermodynamics of biochemical

Enzymes are biological molecules that catalyze biochemical reactions. The thermodynamics of biochemical enzymatic reactions are described in Exhibit 2.10. 

This introductory chapter describes the thermodynamics of biochemical reactions in terms of equilibrium constants and apparent equilibrium constants and avoids references to other thermodynamic properties, which are introduced later. 

The thermodynamics of biochemical rections at specified pH and specified concentrations of coenzymes can be represented by semigrand partition functions. Partition functions are always sums of exponential terms. For a single reactant at specified pH, T has a term for each species that is weighted by a factor that is exponential in AnjijpH. For a mixture of reactants, the partition function T for the system is a product of partition functions of reactants each raised to the power of the number of molecules of the reactant. Thus the partition function for a mixture of reactants is also a summation of exponential terms. For a sum of reactants at specified concentrations of coenzymes, for example, C( the partition function T" is a sum of exponential terms, with a term for each reactant (e.g.,... 

The concepts involved in this approach are simple, but the equations become rather complicated. Biochemical reactions are written in terms of reactants like ATP that are made up of sums of species, and they are referred to as biochemical reactions to differentiate them from the underlying chemical reactions that are written in terms of species. The thermodynamics of biochemical reactions is independent of the properties of the enzymes that catalyze them. However, the fact that enzymes may couple reactions that might otherwise occur separately increases the number of constraints that have to be considered in thermodynamics. 

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