What is the function of aspartate in the urea cycle?

• A. Produces CO₂ for carbamoyl phosphate synthesis.
• B. Provides –NH₂ group as ammonium ion.
• C. Produces succinate for citrulline formation.
• D. Provides the second nitrogen atom for urea.

Answer: (D)

Verified step by step guidance

1. Understand the urea cycle: The urea cycle is a series of biochemical reactions that produce urea from ammonia. It is a crucial process for removing excess nitrogen from the body.
2. Identify the role of aspartate: In the urea cycle, aspartate provides the second nitrogen atom needed for the synthesis of urea.
3. Examine the reaction involving aspartate: Aspartate combines with citrulline to form argininosuccinate, which is then converted to arginine, releasing fumarate.
4. Recognize the importance of nitrogen atoms: Urea contains two nitrogen atoms, one from ammonia and the other from aspartate, highlighting the importance of aspartate in the cycle.
5. Connect the function of aspartate to the overall cycle: By providing the second nitrogen atom, aspartate plays a critical role in the conversion of toxic ammonia into urea, which can be safely excreted from the body.