From which substance are primary bile acids synthesized by hepatocytes?

Primary bile acids are synthesized by hepatocytes from cholesterol. This process is essential for the digestion and absorption of dietary fats. Cholesterol undergoes a series of enzymatic conversions in the liver, resulting in the formation of bile acids, specifically cholic acid and chenodeoxycholic acid. These bile acids then get conjugated with amino acids like glycine or taurine to form bile salts, which play a crucial role in emulsifying fats in the intestine.

The other substances listed do not serve as precursors for bile acid synthesis. Triglycerides and phospholipids are primarily involved in energy storage and membrane structure, respectively, while fatty acids can play various roles in metabolism, but they are not converted into bile acids. Understanding the role of cholesterol in bile acid synthesis is important because it highlights the liver's central function in lipid metabolism and the regulation of fat digestion.