Which of the following statements about plasma lipoproteins is correct? Select one: a) They have a hydrophobic core of triacylglycerol and cholesterol esters b) They have a hydrophobic core of phospholipids and free cholesterol c) They have a hydrophilic core of triacylglycerol and cholesterol esters d) They have a hydrophobic core of phospholipid and apolipoproteins
The Correct Answer and Explanation is:
The correct answer is: a) They have a hydrophobic core of triacylglycerol and cholesterol esters
Explanation:
Plasma lipoproteins are essential molecules that transport lipids such as cholesterol and triacylglycerol through the bloodstream. Lipids are generally hydrophobic and cannot dissolve directly in blood, which is mostly water. To solve this, the body packages lipids into lipoproteins that have a specialized structure enabling lipid transport.
Lipoproteins have a distinct architecture. The core of a lipoprotein particle is hydrophobic, meaning it repels water. This core is primarily composed of triacylglycerols (also known as triglycerides) and cholesterol esters, both of which are non-polar substances. This hydrophobic center safely encloses the lipids away from the aqueous environment of the bloodstream.
Surrounding the hydrophobic core is a monolayer shell made of phospholipids, free cholesterol, and apolipoproteins. The phospholipids and free cholesterol have both hydrophilic (water-attracting) and hydrophobic regions, which helps to stabilize the structure of the lipoprotein in the watery plasma. The hydrophilic portions of the phospholipids and free cholesterol face outward, making the lipoprotein soluble in blood.
Apolipoproteins are proteins embedded within the outer shell. They play vital roles in structural stability, recognition by cell receptors, and activation of enzymes involved in lipid metabolism.
There are different types of plasma lipoproteins, classified based on their density and function. These include chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Despite their differences, all these lipoproteins share the structural characteristic of having a hydrophobic core containing triacylglycerol and cholesterol esters.
Therefore, the correct option is a), describing the true nature of the hydrophobic core structure of plasma lipoproteins.
