Coupon Accepted Successfully!


Plasma Lipids and Lipoproteins


The extraction of the plasma lipids with a suitable lipid solvent and subsequent separation of the extract into various classes of lipids show the presence of: i. Triacylglycerol ; ii. Phospholipids; iii. Cholesterol; iv. Non esterified fatty acids also known as free fatty acids. The latter fraction, the free fatty acids (FFA) is the metabolically and most active form of plasma lipids. Fat absorbed from the diet and lipid synthesized by the liver and adipose tissue must be transported between the various tissues and organs for utilization in the form of plasma lipoproteins. Plasma lipoproteins can be separated by two major methods:


A. Ultracentrifugation:         

B. Electrophoresis:


Major classes of lipoprotein are:

  1. Chylomicrons which transport dietary (exogenous) triglycerides of intestine to blood.
  2. Very low density lipoproteins (VLDL, or pre-β-lipoproteins), transporting endogenous triacylglycerol from liver to blood. It also contain lesser amount of cholesterol.
  3. Low density lipoproteins (LDL, or -lipoproteins) with represents the final stage in catabolism of VLDL and transport plasma cholesterol from liver to tissues.
  4. High density lipoproteins (HDL, or -lipoproteins) which transport plasma cholesterol from tissue to liver. HDL particles are also involved to VLDL and chylomicrons metabolism.

Triacylglycerd is predominant lipid in chylomicrons & VLDL. whereas cholesterol & phospholipids are predominant lipids in LDL & HDL respectively.


Type Found in Site of synthesis Function
AI-I HDL, Chylomicrons Liver, Intestine Major structural protein of HDL, major activator of LCAT  
A-II HDL, Chylomicrons Liver, Intestine Structural protein of HDL, Inhibits lipoprotein lipase (LPL), stimulate hepatic lipase. inhibits LCAT
A-IV HDL, Chylomicrons Intestine Promotes lipoprotein lipase (LPL) mediated triglyceride
A-V Chylomicrons, VLDL Liver lipolysis
B-100 LDL, VLDL, IDL Liver Structural protein of VLDL, IDL; only apoprotein of LDL; mediate uptake of LDL by LDL receptors of liver
B-48 Chylomicrons Intestine Structural protein of chylomicrons
C-I Chylomicrons, VLDL, Liver HDL Liver Inhibits cholesteryl ester transfer protein (CETP),
Activates LCAT and LPL
Activates lipoprotein lipase (major activator)
Inhibits lipoprotein lipase
C-II Chylomicrons, VLDL, HDL
C-III Chylomicrons, VLDL, HDL liver
Apo-D  HDL Spleen, brain, testes, adrenal  
Apo-E Chylomicrons, VLDL, HDL Liver Mediates uptake of chylomicron remnants and IDL by LDL receptors in liver

Test Your Skills Now!
Take a Quiz now
Reviewer Name