We can end this discussion of ATP and the other important high-energy compounds
in biology by discussing the daily metabolic consumption of ATP by humans. An approximate
calculation gives a somewhat surprising and impressive result. Assume
that the average adult human consumes approximately 11,700 kJ (2800 kcal, that is,
2800 Calories) per day. Assume also that the metabolic pathways leading to ATP synthesis
operate at a thermodynamic efficiency of approximately 50%. Thus, of the
11,700 kJ a person consumes as food, about 5860 kJ end up in the form of synthesized
ATP. As indicated earlier, the hydrolysis of 1 mole of ATP yields approximately
50 kJ of free energy under cellular conditions. This means that the body cycles
through 5860/50 117 moles of ATP each day. The disodium salt of ATP has a molecular
weight of 551 g/mol, so an average person hydrolyzes about