Phosphorylation of adp to atp is endergonic, whereas the hydrolysis of atp to adp is exergonic. the two reactions are therefore said to be

The phosphorylation of ADP to ATP and the hydrolysis of ADP to ADP are said to be COUPLED reactions. This is because phosphorylation of ADP to ATP is endergonic, whereas the hydrolysis of ATP to ADP is exergonic. In a coupled reaction, the energy that one process requires is supplied by another process.

only about ten percent of the energy at one trophic level is passed on to organisms at the next trophic level. the remainder of the energy is used in life processes or lost as heat.