Which substance forms micelles for reabsorption by small intestine villi?

Bile salts play a crucial role in the digestion and absorption of dietary fats in the small intestine. They are amphipathic molecules, meaning they possess both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties. This unique structure allows bile salts to emulsify fats, breaking them down into smaller droplets, which increases the surface area for digestive enzymes to act on.

As fats are emulsified, bile salts facilitate the formation of micelles—tiny aggregates of lipid molecules surrounded by bile salts. These micelles transport fatty acids and monoglycerides to the surface of the intestinal villi, where they can be easily absorbed by the enterocytes (intestinal cells). This process is essential for the efficient absorption of lipids from the diet.

In contrast, amylase is an enzyme that breaks down carbohydrates, not fats, while lipase is the enzyme responsible for the hydrolysis of fats but does not form micelles itself. Pepsin is a proteolytic enzyme that digests proteins in the stomach and is not involved in the absorption of fats in the intestine. Thus, bile salts are the key substance that forms micelles to aid in the reabsorption of fats by the small intestine.