Apart from cholesterol, there are several other biologically important lipids (fats) in the body:
Fatty acids and their derivatives. These may be used as an energy source, and are transported in the blood bound to a protein called albumin.
Triglycerides consist of three fatty acids linked to glycerol. Triglycerides are carried in the blood as complexes called lipoproteins.
Phospholipids. These are complex molecules of which the phosphate-containing end is water-soluble, while its lipid end is not. These phospholipids form part of the cell walls, where their water- and lipid-solubility properties help to transport substances into and out of the cells.
Phospholipids and triglycerides are transported in the blood in the form of lipoprotein complexes. These complexes are graded according to size and lipid (fat) content, and there are six of them that are clinically important:
Lipoprotein
Size (nanometres)
% Protein
% Cholesterol
Chylomicrons
75 - 1000
2
3
Chylomicron remnants
30-80
-
-
Very-low density lipoproteins (VLDL)
30-80
8
16
Intermediate density lipoproteins (IDL)
25-40
10
25
Low density lipoproteins (LDL)
20
20
46
High-density lipoproteins (HDL)
7.5-10
50
16
These lipoprotein “shuttles” have specific functions. Of relevance here are:
Chylomicrons. These are large particles that carry dietary fats from the intestine.
LDL. This delivers cholesterol to tissues, where they are either used or deposited. This has earned it the name of “bad cholesterol”.
HDL. This is known as “good cholesterol”, because its main function is to remove cholesterol by carrying it back to the liver for excretion.
Reviewed by Dr A.G. Hall (B.Soc.Sc.(SW), MB,Ch.B)
Last updated: 2008/05/19
Bookmark with:
What are social bookmarks?