What type of molecule mainly composes bile?

Bile is a complex fluid that plays a crucial role in the digestion and absorption of fats. The primary components of bile include bile salts, which are critical for emulsifying fats, bilirubin, which is a byproduct of the breakdown of hemoglobin, cholesterol, and phospholipids.

Bile salts, synthesized from cholesterol in the liver, help to break down dietary fats into smaller molecules, making them easier for digestive enzymes to work on. Bilirubin gives bile its characteristic yellow-green color and is an important indicator of liver function. Cholesterol serves multiple functions, including being a precursor to the bile acids, while phospholipids also assist in fat emulsification.

This combination of components makes bile effective in its digestive roles, particularly in lipid digestion and absorption. The other options do not accurately reflect the main molecular composition of bile, focusing instead on different categories or classes of biomolecules that do not play a direct role in bile's structure or function.