Question: A 70 kg (154 lb) adult requires a calorie intake of 2,000 kcal (8,360 kJ) of food per day. The food is metabolized and the free energy is used to synthesize ATP for useful work. The efficiency of converting food energy into ATP is 50%.
1) Calculate the mass of ATP used by an adult human in 24h. (ATP formula weight = 505 g/mol, DG'° = -30.5 kJ/mol)
2) If ATP is present at 5 mM inside cells, and if the intracellular volume corresponds to about 25% of an adult mass, how frequently is an ATP molecule hydrolyzed and rephosphorylated, on average?