Bile acids that are synthesized in the liver are derived from what substance?

• A. Bilirubin
• B. Fatty acid
• C. Cholesterol
• D. Triglyceride

Answer: (C)

Bile acids synthesized in the liver come from cholesterol. In hepatocytes, cholesterol enters the bile acid synthesis pathway, beginning with the rate-limiting 7α-hydroxylation step that commits cholesterol to becoming primary bile acids (chenodeoxycholic and cholic acids). These acids are then conjugated with glycine or taurine to form bile salts, which are essential for emulsifying fats. Bilirubin, by contrast, is a heme breakdown product and is not used to make bile acids; fatty acids and triglycerides are lipids tied to energy storage and metabolism, not precursors for bile acid synthesis. Thus, cholesterol is the substrate for bile acid production.