What is the only site for oxidation of essential amino acids?

• A. Liver
• B. Heart
• C. Brain
• D. Muscle

Answer: (A)

Amino acid oxidation and nitrogen disposal happen primarily in the liver. When amino acids are catabolized, their amino groups are removed through transamination or deamination, and the resulting ammonia is converted into urea in the liver for excretion. The carbon skeletons are then funneled into energy pathways or glucose production as needed. Because amino acids from the gut are delivered to the liver first via the portal circulation, the liver is positioned to oxidize them efficiently and handle the nitrogen balance. Other tissues can oxidize some amino acids, especially under fasting or high-energy demand, but the liver is the central, most active site for this process, making it the best answer.