Delta G, or the change in Gibbs free energy, represents the change in the max amount of energy available to do non-expansion
work at a given Temp and Pressure. In other words
@ const. T and P.
Exergonic processes have negative Delta G values, which corresponds to the release of energy that can be used to do work.
Endergonic processes have positive Delta G values, which corresponds to the consumption of energy that can be used to do work.
In biological systems, ATP hydrolysis is exergonic, releasing free energy that the cell can use to do work, such as the synthesizing of proteins, which is endergonic and absorbs the free energy released by ATP.