Which receptors are present in the liver for uptake of LDL
**Core Concept**
The liver plays a crucial role in lipid metabolism, including the uptake of low-density lipoprotein (LDL) cholesterol. LDL receptors are responsible for the recognition and internalization of LDL particles, facilitating their breakdown and subsequent cholesterol distribution within the body.
**Why the Correct Answer is Right**
LDL receptors are present on the surface of hepatocytes (liver cells) and are responsible for the endocytosis of LDL particles. These receptors bind to apolipoprotein B-100 (apoB-100) on the surface of LDL particles, triggering a conformational change that allows the receptor-LDL complex to be internalized through clathrin-coated pits. The LDL receptor is a transmembrane receptor that recognizes and binds to LDL particles via its ligand-binding domain. The receptor's cytoplasmic domain also contains a motif that interacts with clathrin, facilitating the formation of clathrin-coated vesicles that internalize the receptor-LDL complex.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely referring to LDL receptors on peripheral cells, such as macrophages or smooth muscle cells, which are not responsible for the hepatic uptake of LDL.
**Option B:** LDL receptors are not present on the surface of adipocytes, which are primarily involved in lipid storage and adipokine secretion.
**Option C:** While LDL receptors are expressed on various cell types, they are not typically associated with the uptake of high-density lipoprotein (HDL) particles, which are involved in reverse cholesterol transport.
**Clinical Pearl / High-Yield Fact**
The LDL receptor is a key regulator of cholesterol homeostasis, and mutations in the LDLR gene can lead to familial hypercholesterolemia, a condition characterized by elevated LDL levels and premature atherosclerosis.
**Correct Answer:** C.