What are micelles?

• A. Protein-lipid complexes
• B. Lipid-bile salt complexes
• C. Nucleic acid-lipid complexes
• D. Carbohydrate-lipid complexes

Answer: (B)

Micelles are aggregates formed by amphipathic molecules in water. In the small intestine, bile salts—amphipathic by nature—group with dietary lipids to form micelles. Their hydrophobic tails tuck inward to trap nonpolar lipids like fatty acids, monoglycerides, cholesterol, and fat-soluble vitamins, while their hydrophilic heads face outward to interact with the watery lumen. This arrangement solubilizes lipids and delivers them to the intestinal lining for absorption, something free lipids cannot do in water. Micelles are defined by this lipid–bile salt association, not by protein–lipid, nucleic acid–lipid, or carbohydrate–lipid complexes.