"A lipoprotein is a biochemical assembly that contains both proteins and lipids, bound to the
proteins, which allow fats to move through the water outside cells and inside cells. The proteins serve to emulsify the lipid (otherwise called fat) molecules. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins. Examples include the high-density (HDL) and low-density (LDL) lipoproteins, which enable fats to be carried in the blood stream, thetransmembrane proteins of the mitochondrion and the chloroplast, and bacterial lipoproteins."
"Lipoproteins may be classified as follows, listed from larger and less dense to smaller and denser. Lipoproteins are larger and less dense when the fat to protein ratio is increased. They are classified on the basis of electrophoresis and ultracentrifugation.
- Chylomicrons carry triglycerides (fat) from the intestines to the liver, to skeletal muscle, and to adipose tissue.
- Very-low-density lipoproteins (VLDL) carry (newly synthesised) triglycerides from the liver to adipose tissue.
- Intermediate-density lipoproteins (IDL) are intermediate between VLDL and LDL. They are not usually detectable in the blood.
- Low-density lipoproteins (LDL) carry cholesterol from the liver to cells of the body. LDLs are sometimes referred to as the "bad cholesterol" lipoprotein.
- High-density lipoproteins (HDL) collect cholesterol from the body's tissues, and bring it back to the liver. HDLs are sometimes referred to as the "good cholesterol" lipoprotein."