ABSTRACT
We can start with a definition of the Standard Free Energy Change, LlGO For a chemical reaction, this is the energy change when 1 mole of reactant A is converted to 1 mole of product B under standard conditions (molar concentra tions and standard temperature and pressure) . This is obviously a very difficult definition to use practically, since A and B would have to be maintained at molar concentra tions throughout the reaction. Most reactions of interest to the biologist do not take place under standard conditions. In addition, the actual free energy changes will depend on the activities (concentrations) of A and B . During a reaction, the chemical potential (J-ti) of each reacting species, i, will alter.
