How Many Moles of ATP are Required to Produce One

Question

How many moles of ATP are required to produce one mole of urea?
A)1
B)5
C)10
D)50

Accepted Answer

The synthesis of one mole of urea in the urea cycle requires 3 moles of ATP directly and 1 mole indirectly (for the synthesis of carbamoyl phosphate), totaling 4 moles. However, since each ATP molecule is hydrolyzed to ADP and inorganic phosphate, releasing two high-energy bonds, the process effectively consumes 2 moles of ATP per mole of urea. Therefore, the correct answer is 5 moles of ATP for the synthesis of one mole of urea, considering the overall energy expenditure in the cycle.