Blood is watery, and cholesterol is fatty; these two do not mix. To travel in the bloodstream, cholesterol is carry in small packages called lipoproteins. This package is made of fat (lipid) on the inside and proteins on the outside.
A lipoprotein is a biochemical assembly that contains both proteins and lipids. This lipid derivative is covalently or non-covalently binds to the proteins. Examples include the high-density and low-density lipoproteins, which enable fats to carry in the blood stream.
Lipoprotein function
Lipoprotein can transport lipids (fats or cholesterol) around the body in the aqueous blood, in which they would not normally dissolve.
Lipoprotein special structure makes them soluble in the salt-water based blood stream. Triglyceride, fats, and cholesterol esters pack internally, shielding it from the water by an outer cover made of proteins.
Lipoprotein classifications
Lipoproteins may classify according to their size and density:
- Larger with less dense
- Smaller with more dense
Lipoproteins are larger and less dense, if they consist of more fat than of protein.
- Chylomicron is transport triacylglycerol (fat) from intestines to liver, skeletal muscle, and to adipose tissue.
- VLDL - Very low-density lipoproteins transport triacylglycerol from the liver to adipose tissue.
- IDL - Intermediate density lipoproteins (size between VLDL to LDL) are not usually detectable in the blood.
- LDL – Low-density lipoproteins or bad cholesterol transport cholesterol from the liver to cells of the body.
- HDL – High-density lipoproteins or good cholesterol, bring back cholesterol from the body's tissues to the liver.