What are the intermediate products before urea is produced?

• A. Ammonia and carbon dioxide
• B. Glucose and ammonia
• C. Uric acid and ammonia
• D. Lactic acid and carbon dioxide

Answer: (A)

Detoxifying ammonia uses the urea cycle, which begins when ammonia combines with carbon dioxide to form the first intermediate, carbamoyl phosphate, in the liver. This step, driven by the enzyme carbamoyl phosphate synthetase I and ATP, sets the stage for the rest of the cycle that eventually yields urea. So the substances entering this pathway just before urea is produced are ammonia and carbon dioxide. The other pairs don’t participate in this initial, essential step of urea formation.