Which of the following is NOT a core component of lipoproteins?

• A. Triglycerides
• B. Free fatty acids
• C. Esterified cholesterol
• D. Phospholipids

Answer: (D)

Lipoproteins have a hydrophobic interior and a polar surface. The interior stores neutral lipids, mainly triglycerides and cholesteryl esters, while the outer surface is made up of phospholipids, free cholesterol, and apolipoproteins to keep the particle soluble in blood. Because phospholipids form that surface layer rather than the interior core, they are not a core component. In contrast, triglycerides and esterified cholesterol are core lipids, so the correct choice is phospholipids.