How is free ammonia (NH3) produced?
Glutamate dehyrogenase removes NH3 from glutamate, making a-ketoglutarate and free ammonia. So… all amino acids pass their amino groups to glutamate, then glutamate gets rid of them as ammonia. “Dear amino acids, please turn in all of your nitrogen to glutamate, and he’ll get rid of it for you.” 13. How does ammonia get secreted from the body? A: It is converted to urea through the urea cycle. Urea is secreted in the urine. 14. “Simple” view of urea cycle: Ammonia (1N) from glutamate combines with CO2 to make carbamoyl phosphate (ATP required). Carbamoyl phosphate (1N) combines with ornithine (1N) to make citrulline (2N). Citrulline gets another nitrogen from aspartate to make arginine (3N). Arginine splits into urea (2N) and ornithine (1N). Ornithine combines with another carbamoyl phosphate to continue the cycle. 15. Where does the urea cycle occur? A: In the cytosol, EXCEPT for reactions involving carbamoyl phosphate. 16. What is the rate-limiting step of urea synthesis? A: The fo
