Which structure is responsible for the formation of micelles during lipid absorption?

The formation of micelles during lipid absorption is primarily facilitated by bile salts. Bile salts are amphipathic molecules that possess both hydrophilic and hydrophobic properties, allowing them to interact with fats and water. When bile salts are secreted into the small intestine, they emulsify dietary fats, breaking them down into smaller droplets. This process increases the surface area available for digestive enzymes, like pancreatic lipase, to act upon.

Once the fats are emulsified, bile salts help form micelles, which are tiny aggregates that transport fatty acids and monoglycerides to the surface of the intestinal absorptive cells (enterocytes). The structure of micelles, with their hydrophilic exterior and hydrophobic core, allows for effective solubilization and transport of lipid digestion products in the aqueous environment of the intestine, making them accessible for absorption into the intestinal cells.

While chylomicrons, fatty acids, and lipoproteins play important roles in lipid digestion and transport after absorption, they are not directly responsible for the formation of micelles during the initial stage of lipid absorption in the small intestine. Thus, bile salts are the key players in this process.