In step 2 of the urea cycle, it appears that one ATP is hydrolyzed, but the actual cost is actually two ATP. Why is this true?

• A. Two ATP molecules hydrolyzing to two ADP molecules release the same amount of energy as the hydrolysis of two molecules of ATP to two molecules of AMP.
• B. Two ATP molecules hydrolyzing to two ADP molecules releases the same amount of energy as the hydrolysis of ATP to AMP.
• C. One ATP molecule hydrolyzing to one ADP molecule releases the same amount of energy as the hydrolysis of two molecules of ATP to two molecules of AMP.
• D. One ATP molecules hydrolyzing to one ADP molecules releases the same amount of energy as the hydrolysis of ATP to AMP.

Answer: (B)