Question

Which three major apoproteins are found in the phospholipid monolayer of HDL? Which two are activating enzymes, and which one is needed for receptor recognition?

a) Apo A-1, Apo A-II, Apo C-II; Activating enzymes: Apo A-I, Apo C-II; Receptor recognition: Apo A-II
b) Apo A-I, Apo A-II, Apo C-II; Activating enzymes: Apo C-II, Apo E; Receptor recognition: Apo A-I
c) Apo A-I, Apo C-II, Apo E; Activating enzymes: Apo A-I, Apo C-II; Receptor recognition: Apo E
d) Apo A-I, Apo C-II, Apo E; Activating enzymes: Apo C-II, Apo E; Receptor recognition: Apo A-I

Answer 1

The three major apoproteins in HDL's monolayer are Apo A-I, Apo C-II, and Apo E. Apo C-II and Apo E are the activating enzymes, while Apo A-I aids in receptor recognition. HDL is vital for cholesterol transport and prevention of atherosclerosis.

Step-by-step explanation:

The three major apoproteins found in the phospholipid monolayer of HDL (high-density lipoproteins) are Apo A-I, Apo A-II, and Apo C-II. Among these, Apo A-I and Apo C-II are the activating enzymes, while Apo A-I is also necessary for receptor recognition. HDL plays a crucial role in transporting cholesterol from tissues back to the liver, preventing atherosclerosis and earning its nickname as the 'good cholesterol' due to its scavenging function. The enzyme lecithin-cholesterol acyltransferase (LCAT) is responsible for esterifying cholesterol within HDL, which can then be transferred to other lipoproteins through the action of cholesteryl ester transfer protein (CETP).

HDL is characterized by a higher protein content relative to its lipid content, contributing to its density and function in lipid metabolism. The correct answer to the question is option d) Apo A-I, Apo C-II, Apo E; Activating enzymes: Apo C-II, Apo E; Receptor recognition: Apo A-I.