This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
The main site of urea synthesis in mammals is: 
Select and explain. 
A. Liver, B. Skin, C. Intestine, D. Kidney
A: Liver
Answer: A: Liver 
Explanation: The intracellular ammonia is immediately trapped by glutamic acid to form glutamine, especially in brain cells. The glutamine is then transported to liver, where the reaction is reversed by the enzyme glutaminase . The ammonia thus generated is immediately detoxified into urea.
Reference: Vasudevan 7th  ed, pg 203