Questions

Lipoproteins are particles that contain triacylglycerol (TAG), cholesterol, phospholipids and amphipathic proteins called apolipoproteins.

The four major types of lipoproteins are

1. chylomicrons,

2. very low-density lipoprotein (VLDL),

3. low-density lipoprotein (LDL), and

4. high-density lipoprotein (HDL).

Chylomicrons are formed in the endoplasmic reticulum in the absorptive cells (enterocytes) of the small intestine.

The function of these lipoproteins is to deliver energy-rich triacylglycerol (TAG) to cells in the body (pink pathway). TAG is stripped from chylomicrons and VLDL through the action of lipoprotein lipase, an enzyme that is found on the surface of endothelial cells. This enzyme digests the TAG to fatty acids and monoglycerides, which can then diffuse into the cell to be oxidized, or in the case of an adipose cell, to be re-synthesized into TAG and stored in the cell.