Which is described as the most important component of HDL?

• A. Phospholipids
• B. Cholesterol Esters
• C. Triglycerides
• D. Apolipoprotein B-100

Answer: (A)

HDL particles are organized with a surface layer rich in phospholipids and free cholesterol that surrounds a hydrophobic core containing cholesterol esters and triglycerides. The phospholipid surface is essential because it provides the amphipathic interface that keeps the particle soluble in blood, enables lipid exchange with other lipoproteins, and serves as the scaffold for apolipoproteins that drive HDL metabolism and function. While cholesterol esters form the core lipid and triglycerides are present in smaller amounts, the phospholipid-rich outer shell defines HDL’s stability and interaction with enzymes like LCAT, making it the most characteristic and important component of HDL among the options. Apolipoprotein B-100 is associated with LDL/VLDL, not HDL, so it’s not a defining HDL component.