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
All of the following are bile acids, EXCEPT: 
Select and explain. 
A. Lithocholic acid, B. Taurocholic acid, C. Deoxycholic acid, D. Chendeoxycholic acid
B: Taurocholic acid
Answer: B: Taurocholic acid 
Explanation: The two principal (primary) bile acids formed in the liver are cholic acid and chenodeoxycholic acid. In the colon, bacteria conve cholic acid to deoxycholic acid and chenodeoxycholic acid to lithocholic acid. Since they are formed by bacterial action, deoxycholic acid and lithocholic acid are called secondary bile acids.