The document discusses lipoproteins, which are complexes of lipids and proteins that transport lipids in the bloodstream. It defines the main classes of lipoproteins - chylomicrons, VLDL, LDL, HDL - and describes their composition, size, density, functions, and roles in lipid transport. Diseases associated with abnormalities in lipoprotein metabolism are also summarized, such as hyperlipoproteinemias which result from defects in the synthesis or catabolism of specific lipoproteins.

1. Always behave
like a DUCK
Keep calm and unruffled
on the surface
But
Paddle with great vigor underneath
Dr. Dhiraj J. Trivedi

2. Lipoprotein
and
its Metabolism

3. What is lipoproteins?
• Lipoproteins are spherical,
macromolecular complexes of lipids and
specific protein called
Apo-protein.

4. What are the functions of
lipoproteins?
• 1. They keep water insoluble lipids in solution
of aqueous plasma.
• 2. Provide mechanism for transporting their
lipid components to and from the tissue.

5. What is the general composition
of plasma lipoproteins?
They contain neutral lipid core
made of TG , Cholesteryl esters
and shell of amphipathic
phospholipids,
Unesterified cholesterol
and apoprotein.

6. HOW ARE THE LIPOPROTEINS
CLASSIFIED?
Classified on the basis of
1.COMPOSITION
2.DENSITY and
3.ELECTRO PHORETIC
MOBILITY

7. Name the classes of
lipoproteins?
• 1. Chylomicron
• 2. Very low density lipoproteins (VLDL).
• 3. Low density lipoproteins (LDL).
• 4. High density lipoproteins (HDL).
• 5. Free fatty acids – Albumin complex

8. Arrangement of lipoprotein on
their
Size and Density
Lipoprotein
class
Size Density
Chylomicrone 1000 to 10,000A Less than 0.96
VLDL 300 to 700A Upto 1.006
LDL 150 to 250A Upto 1.063
HDL 75 to 100A Above 1.063

9. Lipoprotein composition
TG C &
CE
PL Apo
protein
Chylo-
microne
90 % 5 % 3 % 2 %
VLDL 60 % 20 % 15 % 5 %
LDL 08 % 50 % 22 % 20 %
HDL 05 % 25 % 30 % 40 %

10. Electrophoretic mobilityDensity

11. Lipoprotein molecule

12. Write the functions of apolipoproteins.
• 1. Provide recognition sites for cell surface
receptors.
• 2. Serves as coenzymes
• 3. Some are required as a structural part and
can not be replaced or removed.

13. Write the functions of
CHYLOMICRONES.
• Transport mainly
Exogenous Tri acyl
glycerol from
intestine to Liver,
adipose tissue and
muscle.
• TAG either
absorbed from food
or Synthesized in
enterocytes )
Adipose
Muscle

14. Write the functions of
Very Low Density Lipoproteins ( VLDL )
• Transports mainly
endogenous Tri acyl
glycerol from Liver to
extra hepatic tissues
• Endogenous Tri acyl
glycerol Synthesized
in hepatocyte

15. Write the functions of
Low Density Lipoproteins (LDL)
• Transports mainly
Cholesterol and
cholesteryl esters
from Liver to extra
hepatic tissues
cholesterol

16. Write the functions of
High Density Lipoproteins (HDL)
• Transports mainly
Cholesterol and
Cholesteryl esters
from extra hepatic
tissues to Liver
• Serves to hold apo-
c & apo-e for use
cholesterol

17. Write the functions of
Free fatty acid Albumin complex
• Transports mainly
free fatty acids
released from
adipose tissue to
Liver for
oxidation
FFA
Adipose
Adipose
Adipose
FFA
FFA
FFA

18. Enzymes in lipoprotein
metabolism
• Lecithin cholesterol acyl transferase
• L CAT :
• Catalyses transfer of Sn2 FA of phospholipids
to cholesterol.
• Converts polar cholesterol to non polar
cholesteryl esters
• Shift of cholesterol form periphery to core

19. • Lipoprotein lipase
• Heparin sensitive lipase
Catalyses hydrolysis of chylomicron
and VLDL
Located on capillary surface
Responsible for generating FA and
glycerol in tissue
Enzymes in lipoprotein
metabolism

20. • Hepatic lipase
Catalyses hydrolysis of TAG and
Phospholipids of HDL and IDL
Located in sinusoid s of liver
Responsible for metabolic degradation
of HDL and IDL
Enzymes in lipoprotein
metabolism

21. • Acid lipase
• Intracellular lipase
Catalyses hydrolysis of TAG and
cholesteryl esters in lysosomes
Located in lysosome ,
Optimum pH acidic
Responsible for degradation of
lipoprotein taken up by receptor
mediated endocytosis
Enzymes in lipoprotein
metabolism

22. Lipoprotein
Receptors
E
B10
0
E
Receptor for
chylomicron
remnants
Receptor for
LDL and IDL
X
unknownReceptor for
HDL
Receptor for
LDL does not
recognize VLDL
due to presence
of C ii
Apo C ac t as coenzyme for lipo protein lipase

23. METABOLISM OF
CHYLOMICRONS
Lipoprotein metabolism
1

24. Type I
Hyper LP
Lplipase def
Apo Cii def

25. METABOLISM OF VLDL AND
LDL
Lipoprotein metabolism
2

26. Type III
Hyper LP
Fatty liver
Type II
Hyper LPLDL not
removed

27. CELLUAR UPTAKE
AND
DEGRADATION OF LDL
Lipoprotein metabolism
3

29. Receptor mediated Endocytosis

30. METABOLISM OF HDL
Lipoprotein metabolism
4

31. VLD
L
VLD
L
LCAT

32. Apo – A1
Apo – B
Bad cholesterol
LDL
Good cholesterol
HDL

33. Lipoproteins and Disease
• Hyperlipoproteinemias and
hypolipoproteinemias are due to
malfunctions in the synthesis and
catabolism of lipoproteins.

34. HYPERLIPOPROTEINEMIA
TYPE -- I
Deficiency of enzyme lipoprotein
lipase
VLDL and Chylomicrons are not
utilized
High TAG level in the blood

35. HYPERLIPOPROTEINEMIA
TYPE -- II
Lack of removal of LDL form the blood
Not recognising Apo B100 in LDL receptor
High Cholesterol level in the blood
High risk of CHD and Atherosclerosis

36. HYPERLIPOPROTEINEMIA
TYPE -- III
Deficiency of enzyme mobilising
VLDL and LDL from circulation
Apo E deficient, impairs uptake
IDL level increase in the blood

37. HYPERLIPOPROTEINEMIA
TYPE -- IV
Due to imbalance between
synthesis and clearance of VLDL
in circulation

38. HYPERLIPOPROTEINEMIA
TYPE -- V
Lipoprotein lipase deficient or
utilisation of VLDL and
Chylomicrons

39. HYPO LIPOPROTEINEMIA
A BETA LIPOPROTEINEMIA
1. Serum LDL and VLDL level
decreased due to absence of Apo B
2. Lack of formation of Chylomicron
after high fatty meal
3. Result malabsorption, steatorrhea
and cholesterol deposition under
skin as nodules

40. HYPO LIPOPROTEINEMIA – II
Tangier disease
1. Deficiency of Serum HDL due
to absence of Apo A1
2. Result cholesterol ester
deposition in skin , cornea and
blood vessels.
3. Increased risk of premature
CHD

41. Diseases Genetic defects Risk
LPL defect Reduced level of LPL Pancreatitis
Apo C-11 defect Inability to synthesize
Apo C-11
Pancreatitis
A beta
lipoproteinemia
Inability to synthesize
Apo B
Neurological defect
An alpha
lipoproteinemia
Inability to synthesize
Apo A
Cholesteryl esters
storage in abnormal
sites
Diseases associated with lipoprotein metabolism

42. Apo B48
Apo A
Intestinal mucosa
Liver
Choesterol
Fatty acid
Apo A
Apo C
Apo E
E
Receptor for
chylomicron
remnants
B48
chylomicron
remnants
B48E
AE
C II
HDL
Ch
PL
Ch
TAG
Ch
TAG
Glycerol
Free FA
Lipoprotein
lipase
C IIE
Nacent
chylomicron
A
E
C II
CM
Ch
PL
B48
A
1
2
3
4

43. Thank you