Blood is watery, and
cholesterol is fatty, these two do not mix. To travel in the
bloodstream, cholesterol is carried in small packages called
lipoproteins. The small packages are made of fat (lipid) on the inside
and proteins on the outside.
A lipoprotein is a biochemical
assembly that contains both proteins and lipids. The lipids or their
derivatives may be covalently or non-covalently bound to the proteins.
Examples include the high density and low density lipoproteins which
enable fats to be carried 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 are packed
internally, shielding it from the water by an outer cover made out of
proteins.
Lipoprotein classifications
Lipoproteins may be classified according to their size and density;
- Larger in size with less dense.
- Smaller in size with denser.
Lipoproteins are larger in size and less dense, if they consist of more fat than of protein.
- Chylomicrons transport triacylglycerol (fat) from the intestines to the 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.
