Once absorption across the wall of the small intestine has occurred, free fatty acids are transported in the blood by binding to the protein albumin. Cholesterol, however, is transported by a special class of molecules called lipoproteins. Lipoproteins are comprised of an inner core of cholesterol that is hydrophobic and are encased by an outer protein shell.
Some very important lipoproteins are:
- Very low density lipoprotein (VLDL)
- Low density lipoprotein (LDL)
- High density lipoprotein (HDL)
Lipoproteins are placed into one of these categories depending on their density. Realize that lipids are NOT dense molecules. Proteins, on the other hand, are dense. Therefore, higher lipid levels result in a lower density lipoprotein. Higher amounts of protein result in a denser lipoprotein molecule.