Lipoproteins are biochemical assemblies of proteins and lipids that transport lipids through the bloodstream. They consist of a hydrophobic core of lipids surrounded by a membrane containing phospholipids, free cholesterol, and apolipoproteins. Lipoproteins are classified based on density into chylomicrons, VLDL, IDL, LDL, and HDL. Chylomicrons and VLDL carry triglycerides from the intestine and liver to tissues, while HDL and LDL transport cholesterol. High LDL and low HDL levels increase the risk of atherosclerosis and heart disease. A balanced diet high in fish, nuts, and fiber can lower LDL and raise HDL to reduce disease risk.

1. Lipoprotein
Structure and Function
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By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. Contents
• Introduction
• General structure of lipoprotein
• Apo lipoprotein
• Classification of lipoprotein
• Chylomicron
• LDL- low density lipoprotein
• HDL- high density lipoprotein
• VLDL- very low density lipoprotein
• IDL- intermediate density lipoprotein
• Clinical disorders
• Preventive measures
• Lipoprotein analysis
• Diet , cholesterol and lipoprotein
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3. Introduction
• A lipoprotein is a biochemical assembly
between simple soluble proteins and non soluble
fats ( cholesterol and triglycerides).
• The main function of lipoprotein is to transport
the lipid through the blood and lymphatic
system to the various cells throughout the body.
• The lipoprotein in short can be said as“ oil
tanker”.
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4. General structure of lipoprotein
• Lipoproteins are complex particles that have a
central hydrophobic core of non-polar lipids,
primilarly cholesterol and triglycerides.
• The hydrophobic core is surrounded by a
hydrophilic membrane consisting of
phospholipids free cholesterol and
apolipoprotein.
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5. Apolipoproteins
• The protein components of
lipoproteins are known as
apolipoproteins or just
apoproteins .
• Apolipoproteins have
amphipathic helices that
coat lipoprotein surfaces .
• Outer protein “shell” of the
lipoprotein molecule .
• Apolipoproteins are
embedded in the membrane
, both stabilizing the
complex & giving it
functional identity . 5

6. Functions of Apolipoprotein
• They can form part of the structure of the
lipoprotein. E.g. Apo B structural component
of VLDL and chylomicrons.
• They can be enzyme cofactors or enzyme
inhibitors. C-II for lipoprotein lipase as
cofactors and Apo A-II and Apo C-III for
lipoprotein lipase.
• They act as ligands for interaction with
lipoprotein receptors in tissues. For e.g. Apo B
-100 and Apo E for LDL receptor and Apo A-1
for the HDL receptor. 6

7. https://www.labce.com/spg659280_apolipoproteins.aspx 7

8. Classification of Lipoprotein
• Lipoprotein can be classified into 3 types:
1. On the basis of density: lipoprotein are separated
by ultracentrifugation .These are of 5 types.
a. LDL ( low density lipoprotein)
b. HDL( high density lipoprotein)
c. Chylomicron
d. IDL ( Intermediate density lipoprotein)
e. VLDL( very low density lipoproteins )
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9. 9

10. 2. Based on electrophoretic mobilities:
• Lipoproteins may be separated according to
their electrophoretic properties into α, preβ,β
and broad beta lipoprotein.
• The mobility of lipoprotein is mainly
dependent upon protein content.
• Those with higher protein content will move
faster towards the anode and those with
minimum protein content will have minimum
mobility.
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11. • HDL are α, VLDL are pre beta , LDL are beta
and IDL are broad beta lipoprotein.
• Chylomicrons remains at the origin because
they have the high lipid content.
• VLDLs with less protein content than LDL
move faster than LDL , this is due to nature of
apoprotein present.
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12. Lipoprotein Electrophoresis
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13. 3. based on the nature of apolipoprotein content:
• One or more apoprotein are present in each
lipoprotein.
• The major apolipoprotein of HDL are
designated as A.
• The main apolipoprotein of LDL is
apolipoprotein B (B-100) which is synthesized
in liver. Apolipoprotein B is also found in
VLDL.
• Chylomicrons contain a truncated form of
apolipoprotein B (B-48) that is synthesizes in
the intestine.
• Apolipoprotein E is found in VLDL, HDL, and
chylomicrons.
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14. CHYLOMICRON
• Chylomicrons are the lipoprotein particles that
consist of:
Triglycerides (85-92%)
Phospholipids (6-12%)
Cholesterol (1-3%)
Proteins ( 1-2%)
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15. Functions of chylomicrons: Chylomicrons
transport lipids absorbed from the intestine to
adipose, cardiac and skeletal muscle tissue
where there triglycerides components are
hydrolyzed by the activity of lipoprotein lipase
and the free released fatty acids are absorbed
by the tissues.
• The enzyme lipoprotein lipase, with
apolipoprotein C-II as a cofactor help in the
process of hydrolization.
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16. VERY-LOW DENSITY LIPOPROTEIN
• It is a type of lipoprotein made by the liver.
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17. • As similar to chylomicrons VLDL also
contains triacylglycerol but in the case of
VLDL triacylglycerol comes from the excess
fatty acids as a consequences of
carbohydrates in the diet.
• Addition to triacylglycerol VLDL contains
around 35% of free esterified cholesterol 35%
phospholipids, and various apolipoprotein
including Apo B-100
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18. LOW DENSITY LIPOPROTEIN
• Low density lipoprotein contains the highest
percentage of cholesterol. It I a combination of
10-15% triglycerides, 45% cholesterol, 22%
phospholipids, and 25% lipids.
• The main function of LDL are the formation of
cell wall, vitamin D synthesis, and helping in
the production of certain hormones.
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19. • High LDL cholesterol
levels lead to the formation
of plaques on the inner wall
surfaces of the arteries.
This increases the chances
of the individual to
cardiovascular events such
as heart attack and stroke.
That is why LDL is
referred to as the bad
cholesterol.
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20. Bad vs. Good Cholesterol
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21. HIGH DENSITY LIPOPROTEIN
• HDL lipoprotein has the smallest particle size
of all the lipoprotein. They carry about 25 to
335 of all the cholesterol in the blood.
• Their composition consist of 55% protein,3-
15% triglycerides,26-46% phospholipids and
2-10% cholesterol.
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22. Structure of HDL
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23. • The main benefit of HDL is that it carries the
excess LDL, particles from the cells back to
the liver to be processed and got rid of through
the bile of the intestines. This process is
known as reverse cholesterol transport.
• The desirable levels of HDL stand at 40 mg/dl.
But to have levels at 60 mg/dl is very good and
protects you from cardiovascular
complications.
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24. Intermediate Density Lipoproteins
• Intermediate density lipoproteins is another
lipoprotein that enables fats and cholesterol to
move freely through the water based
bloodstream.
• IDLs are smaller in size that VLDL.
• They are composed of 10-12% protein, 24-
30% triglycerides,25-27% phospholipids and
8-10% cholesterol.
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25. • IDL transports endogenous triglyceride fats
and cholesterol through the blood from the
liver to the tissues and its high level can
promote the formation of atherosclerosis.
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26. CLINICAL DISORDERS
ATHEROSCLEROSIS
• Atherosclerosis is a slowly progressive
disease of muscular arteries and large arteries
characterized by the elevated deposition of
cholesterol in the from of plaque.
• Plaque formation can cause complications like
heart attack, stroke, chest pain.
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28. HYPERLIPIDEMIA
• Hyperlipidemia is abnormally elevated levels
of any or all lipids/lipoproteins in blood .
• It is divided into primary & secondary
subtypes .
• Primary hyperlipidemia is usually due to
genetic causes (such as a mutation in a
receptor protein) while secondary arises due to
other underlying causes such as diabetes .
• These are regarded as modifiable risk factors
for cardiovascular disease .
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29. PREVENTIVE MEASURES
• Maintaining a proper balance diet.
• Exercise daily.
• Weight control ( avoid junk food )
• Stop alcohol consumption.
• Stop smoking.
• Diet maintenance.
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30. Lipoprotein Analysis
• Laboratory measurement of the lipoproteins is
important because of their association with
Coronary Artery Disease ( CAD )
• CAD is the first cause of premature death in the
United States
• Because of its connection with public health,
lipid testing and interpretation has been
standardized to provide consistent results that
can be utilized for the risk assessment of CAD
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31. • Reference range of lipoproteins
–Total Cholesterol 140 - 200 mg / dl
–HDL 30 - 75 mg / dl
–LDL 55 - 130 mg / dl
–Triglycerides 65 - 155 mg / dl
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32. Diet, cholesterol and lipoprotein
Fish & fish oils
• Fatty fish such as salmon , tuna , etc. have
high levels of omega – 3 fatty acids , which are
known to increase HDL cholesterol .
• On the plus side , these omega -3’s lower your
triglycerides , which are the main cause of
obesity, diabetes etc.
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33. Nuts & Seeds
• Nuts such as almonds , walnuts & cashews are
rich in heart – healthy unsaturated fat & help
to lower LDL cholesterol & triglycerides .
Fruits , Grains & Beans
• Foods rich in soluble fiber include fruits like
apples , peas & grains , lowers LDL
cholesterol .
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34. Conclusion
• Lipoproteins are mainly the combinations of
lipid and protein.
• Their main function is to transport triglycerol
and cholesterol into blood plasma.
• On the basis of density they are classified into
five types.
• HDL are the good cholesterol and LDL are the
bad cholesterol.
• We should take balance diet in order to
increase the level of HDL in our body.
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35. References
• Molecular Cell biology by Lodish H. fifth
edition 2003.
• Internet source:
https://www.google.co.in/amp/healthvigil.com
• https://www.labce.com/spg659280_apolipopro
teins.aspx
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