Which of the following apolipoproteins is synthesized in the liver as pa of the coat of very low-density lipoproteins (VLDLs)?
**Core Concept**
The question is testing the student's knowledge of apolipoproteins, which are essential components of lipoproteins involved in lipid transport in the body. The specific apolipoprotein being asked about is a key component of very low-density lipoproteins (VLDLs), which are synthesized in the liver and play a crucial role in the transport of endogenous triglycerides from the liver to peripheral tissues.
**Why the Correct Answer is Right**
Apolipoprotein B-100 (ApoB-100) is synthesized in the liver as part of the coat of VLDLs. ApoB-100 serves as the primary apolipoprotein component of VLDLs and is essential for the assembly and secretion of VLDLs from the liver. As VLDLs are converted to intermediate-density lipoproteins (IDLs) and eventually low-density lipoproteins (LDLs), ApoB-100 remains attached to the lipoprotein particle, serving as a ligand for the LDL receptor. This process is critical for the regulation of cholesterol levels in the body.
**Why Each Wrong Option is Incorrect**
* **Option A:** Apolipoprotein A-I (ApoA-I) is a major component of high-density lipoproteins (HDLs) and is synthesized in the small intestine, not the liver.
* **Option B:** Apolipoprotein C-II (ApoC-II) is a cofactor for lipoprotein lipase and is present on VLDLs and HDLs, but it is not synthesized as part of the coat of VLDLs.
* **Option D:** Apolipoprotein E (ApoE) is present on VLDLs, IDLs, and HDLs and plays a role in the clearance of lipoproteins from the bloodstream, but it is not synthesized as part of the coat of VLDLs.
**Clinical Pearl / High-Yield Fact**
Apolipoprotein B-100 is a key marker of cardiovascular risk, and elevated levels of ApoB-100 are associated with an increased risk of atherosclerotic disease.
**Correct Answer:** C. Apolipoprotein B-100