Question

Calculate the amount of ATP in kg that is turned over by a resting human every 24 hours. Assume that a typical human contains ~50g of ATP (Mr 505) and consumes ~8000 kJ of energy in food each day. The energy stored in the terminal anhydride bond of ATP under standard conditions is 30.6 kJmol-1. Assume also that the dietary energy is channeled through ATP with an energy transfer efficiency of ~50%. Express your answer to two significant figures, and don't forget units!

Answer 1

Given,

1. ADP + Pi ----------------> ATP , dG= + 30.6kJ mol^-1 --- equation 1

2. Efficiency of reaction 1 = 50%

That is only 50% of 8000 kJ energy taken in for of food is converted into ATP.

Thus, total amount of energy stored in terminal phosphate group of ATP = 50 % of 8000 kJ

                        = 4000 kJ.

The number of moles of ATP produced from 4000 kJ energy (using equation 1)=

            4000 kJ / (energy required to form 1 ATP molecule)

            = 4000 kJ/ 30.6 kJ mol^-1

            = 130.71895 mol

Molecular mass of 130.71895 mol = Number of moles x molecular mass

                                                = 130.71895 mol x 505 g mol^-1

                                                = 66013.071895 gram

                                                = 66.01 kg

Therefore, daily turnover of ATP = 66.01 kg day^-1