Which lipoprotein particle is primarily responsible for delivering cholesterol to peripheral tissues and is often labeled as 'bad cholesterol'?

• A. High-density lipoprotein
• B. Low-density lipoprotein
• C. Very low-density lipoprotein
• D. Chylomicrons

Answer: (B)

Delivering cholesterol to peripheral tissues is the job of low-density lipoprotein. LDL forms from the metabolism of VLDL as triglycerides are removed in circulation, and it carries cholesterol esters to cells throughout the body by binding LDL receptors and being taken up via endocytosis. This delivery supports membrane synthesis and steroid production, but when LDL levels are high, excessive cholesterol can accumulate in arterial walls, promoting plaque formation and atherosclerosis. That association with cardiovascular risk is why this particle is often labeled “bad cholesterol.”

In contrast, HDL is involved in reverse cholesterol transport, pulling cholesterol away from tissues back to the liver; chylomicrons mainly deliver dietary triglycerides from the intestine, and VLDL transports endogenous triglycerides and cholesterol from the liver, becoming LDL as triglycerides are released.