Which compound constitutes nearly half of the NPN substances in the blood?

Which compound constitutes nearly half of the NPN substances in the blood?

• A. Ammonia
• B. Creatine
• C. Urea
• D. Uric acid

Answer: (C)

Most non-protein nitrogen in the blood is urea, the end product of the liver’s processing of excess nitrogen from amino acid breakdown. After proteins are degraded, ammonia is formed, and the liver converts most of it into urea for safe transport in the bloodstream to the kidneys for excretion. Because urea is the primary nitrogenous waste circulating in the blood, it accounts for roughly half of the total NPN substances in healthy individuals. Ammonia stays at very low levels due to this conversion, while creatinine and uric acid come from other processes and usually exist in smaller amounts. So, urea is the dominant NPN compound in the blood.

Most non-protein nitrogen in the blood is urea, the end product of the liver’s processing of excess nitrogen from amino acid breakdown. After proteins are degraded, ammonia is formed, and the liver converts most of it into urea for safe transport in the bloodstream to the kidneys for excretion. Because urea is the primary nitrogenous waste circulating in the blood, it accounts for roughly half of the total NPN substances in healthy individuals. Ammonia stays at very low levels due to this conversion, while creatinine and uric acid come from other processes and usually exist in smaller amounts. So, urea is the dominant NPN compound in the blood.