Let's analyze each of the statements provided regarding the urea cycle:
1. **The two nitrogen atoms that are incorporated into urea enter the cycle as ammonium and arginine.**
- This statement is **incorrect**. The two nitrogen atoms in urea are derived from one being contributed by ammonia (NH4+) and the other from aspartate, not arginine.
2. **Urea is produced directly by the hydrolysis of argininosuccinate.**
- This statement is