Important Points about G

1. Three important terms relating to the free energy change of a process are:

> - the total free energy change for a reaction under any conditions

> - free energy under standard conditions (all concentrations of 1M)

> , the free energy change under standard biological conditions (all concentrations 1M, [H 2O] = constant, and pH = 7.0)

Thus, a positive may influence a reaction, but cellular conditions may make the overall for the reaction negative.

2. and only determines whether a reaction is favorable as written.. Only when is negative is a reaction favored. The sign of or does not determine the direction a reaction will proceed.

3. depends on temperature ( = H - TS). This can be a factor for a given reaction occurring in different organisms living under very different conditions of temperature.

See also: Free Energy and Useful Work, Free Energy and Concentration, Free Energy Change and the Equilibrium Constant