Enzymatic cleavage of one of the phosphate ester bonds of ATP to yield ADP and a single phosphate molecule known as orthophosphate (designated as ?,). The cleavage of the phosphate bond is energy-yielding and is (except in the case of a futile cycle) coupled enzymatically to reactions that utilize the energy to run the cell. An orthophosphate cleavage reaction releases relatively less energy than does a corresponding pyrophosphate cleavage reaction.