1. Lipoprotein
Definition :
A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to
the proteins. 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, the transmembrane proteins of
the mitochondrion and the chloroplast, and bacterial lipoproteins.
Classifications :
1- By density :
Lipoproteins may be classified as follows, listed from larger and less dense to smaller and
denser. Lipoproteins are larger and less dense, if they consist of more fat than of protein. 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) triacylglycerol 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.
Diameter % % % %
Density (g/mL) Class
(nm) protein cholesterol phospholipid triacylglycerol
>1.063 HDL 5–15 33 30 29 4
1.019–1.063 LDL 18–28 25 50 21 8
1.006–1.019 IDL 25–50 18 29 22 31
0.95–1.006 VLDL 30–80 10 22 18 50
<0.95 Chylomicrons 100-1000 <2 8 7 84
[2]

2. 2- Alpha and beta :
3- It is also possible to classify lipoproteins as "alpha" and "beta", according to the
classification of proteins in serum protein electrophoresis. This terminology is sometimes
used in describing lipid disorders such as Abetalipoproteinemia.
3-Lipoprotein(a):
Lipoprotein(a) – Lp(a), Cardiology diagnostic tests
< 14 mg/dL : Normal
14-19 mg/dL : ?
> 19 mg/dL : High risk