A. Size
The relative size of plasma lipoproteins according to their hydrated density is shown in Fig. 1. Hydrophobic lipids (cholesterol, cholesteryl esters, phospholipids, and triglyc-erides) are transported in the blood by lipoprotein particles, which are complex water-soluble particles that provide water-soluble transport packages.
B. Function
Lipoproteins provide a transport for lipids as described below.
1. Transport of cholesterol to organs and tissues; choles¬terol is required for the formation of membranes of red blood cells and for the production of steroid hormones. In the liver it is converted to bile acids. Triglycerides absorbed from the intestine are carried to the liver and other sites of utilization and storage. Dietary fatty acids are transported.
Food fats are absorbed as fatty acids and packaged into very large lipoproteins called the chylomicrons. These are released from the gut into the portal system of veins that transport blood from the gut to the liver (see Fig. 2).
C. Types
The major circulating lipoproteins are
a diameter greater cleared from the
1. Chylomicron remnants that have than 300 nm and are rapidly circulation.
2. Very low density lipoproteins (VLDLs) that carry triglycerides and have a particle diameter between 300 and 800 nm.

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