Lipoprotein classes – How many major types of lipoproteins are recognized in human plasma based on density and composition?

Introduction / Context:
Lipoproteins package hydrophobic lipids for transport in blood. Classifying them by density and apolipoprotein content is essential for understanding lipid metabolism and cardiovascular risk profiles.

Given Data / Assumptions:

• The classical plasma lipoprotein classes are chylomicrons, VLDL, IDL, LDL, and HDL.
• Each class differs in lipid/protein ratio, size, and metabolic fate.
• Clinical assays often report LDL and HDL cholesterol; VLDL and IDL are also clinically relevant.

Concept / Approach:
Counting the major classes yields five. While subclasses exist (e.g., HDL2 vs HDL3; small dense LDL), the principal categories used in textbooks and diagnostics remain five.

Step-by-Step Solution:

Verification / Alternative check:
Ultracentrifugation and electrophoretic methods reproducibly resolve these five major classes; clinical guidelines reference them.

Why Other Options Are Wrong:

• 2, 4: underestimate; 6 or 8: would count subclasses or nonstandard categories.

Common Pitfalls:
Confusing subclasses with major classes, leading to overcounting.

Final Answer:
5