**Core Concept**
Cholesterol is constantly being transferred between cells through a process called reverse cholesterol transport. This process is essential for maintaining cholesterol balance in the body. The transfer of cholesterol from membrane turnover is facilitated by specific classes of lipoproteins.
**Why the Correct Answer is Right**
The correct class of lipoproteins that transfers cholesterol from membrane turnover is **High-Density Lipoprotein (HDL)**. HDL plays a crucial role in reverse cholesterol transport by picking up excess cholesterol from peripheral tissues and transferring it to the liver for excretion. This process is mediated by the enzyme **lecithin-cholesterol acyltransferase (LCAT)**, which esterifies cholesterol for transport. HDL's role in cholesterol transfer is essential for maintaining healthy cholesterol levels and preventing atherosclerosis.
**Why Each Wrong Option is Incorrect**
* **Option A:** Low-Density Lipoprotein (LDL) is involved in transporting cholesterol to peripheral tissues, not from them. It is often referred to as "bad cholesterol."
* **Option B:** Very-Low-Density Lipoprotein (VLDL) primarily transports endogenous triglycerides from the liver to adipose tissue and muscle, not cholesterol from membrane turnover.
* **Option D:** Chylomicrons are involved in transporting exogenous triglycerides from the intestines to adipose tissue and muscle, not cholesterol from membrane turnover.
**Clinical Pearl / High-Yield Fact**
Mnemonics like "HDL is Happy to Help" can help remember that HDL is involved in reverse cholesterol transport, while "LDL is Lousy for Lungs" highlights its role in transporting cholesterol to peripheral tissues.
**Correct Answer:** C.
Free Medical MCQs Β· NEET PG Β· USMLE Β· AIIMS
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