Lipoprotein

Lipoprotein
VLDL:

Synthesized inLiver.
Mostly composed of TG.

Lipid 90-93%

Function:
Transport TG from liver to peripheral tissue.

Metabolism :
Extrahepatic tissue by lipoprotein lipase

Metabolic end product:
FFA
Glycerol
IDL/VLDL remnent

Fate:
Taken by liver
converted to LDL

LDL:

Composed of 79% lipid
Protein 21%

Contains cholesterol and cholesterol ester.

Derived from VLDL in the plasma

Chief pathogenic factor for atherosclerosis.

Functions:
Provides cholesterol to peripheral tissues.

Metabolism:
30% extrahepatic tissue
70% inside liver.

HDL:

Lipid 33%
Protein 67%

Synthesized inside the liver.

Function:
Transport Cholesterol from peripheral tissue to liver.

Usually biconcave shape. When it picks up cholesterol it become round.

Transfer cholesterol to VLDL,LDL in exchange of TAG/TG
carry CE(ester) to liver
Remove free cholesterol from extrahepatic tissue by LCAT(lecithin cholesterol actyl transferase)
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Lipoprotein
Protein part of lipoprotein is called apo protein.

Types of lipoprotein:
1. Chylomicron
2.VLDL(very low density lipoprotein)
3.LDL
4.HDL

Here one should be noted density will decrease if lipid amount increase.
So in VLDL, lipid is much more than in HDL

another matter;
Increase protein causes the increase elecrophoric mobility.


Basics of apoprotein:
maintenance the shape of liupoprotein.
B100. the apoprotein which synthesize by B gene 100%
B48... B gene synthesize 48% of the protein.


metabolism of Lipoprotein:

Chylomicron:
Site of synthesis: Small intestine.
Size 100 nano m
Low density
combines with C1,11,111 E in circulation.

lipid 98-99%
Protein 1%

Functions:
Transport dietary TG,Cholesterol,Cholesterol Ester from instestine to peripheral
tissue.

Metabolism:
Extrahepatic tissue by lipoprotein lipase.

Metabolic end product:
FFA
Glycerol
Chylomicron remnant(Removed by liver )
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Metabolism of TG/Triacyl glycerol
TG is consit of three molecule of fatty acid esterified into glycerol.

Storage:

Main storage: Adipose cell. Most of TG deposite as droplet.
Other store: Liver and muscle cell, Store small amount of TG.

Fate of TG:

1. Fate of Adipose tissue TG:
Store in cytosol as depot fat.
Ready to mobilize when body require fuel.
2. Liver: TG is packed with cholesterol, Cholesterol ester
Phospholopid ,protein forms various lipoprotein.

Biosynthesis:
Site : liver and adipose tissue.

Source : FFA.(free fatty acid)

Lipolysis of TG:

hydrolysis of TG is called lipolysis.

Enzyme required:
Lipase.
a. In adipose tissue: Hormone sensitive lipase.
b. In vessles. Lipoprotein lipase(chylomicron, VLDL)

hormone sensitive lipase
TG......................................................>>>DAG(diacylglycerol)+FFA


DAG....................................................>>>MAG+FFA

MAG..................................................>>>Glycerol+FFA

So the products of lipolysis are:
a. FFA
b.Glycerol

Fate of Glycerol:
a.In adipose tisssue..Can not utilize glycerol as there is no enzyme to metabolise
So glycerol is the excellent index of glycolysis in adipose tissue.
b.In liver. glycerol is converted to glycerol phosphate by glycerol kinase.
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Absorption of lipid
Primary product of lipid degradation are:
a. FFA
b.2-monoglycerol
c.Cholesterol.

Absorption:

Site of absorption:
Brush border of intestinal mucosal cell.

process of absorption:

Short and Medium chain fatty acid absorbs into directly into portal vein
Long chain fatty acid and 2-monoglycerol absorbs by brush border forming micelle.
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Tuesday, May 25, 2010Composition of Dietary lipid
TG
Sterol(Cholesterol)
Sterol Ester
Phospholipid

Fat.... Are all triester of tri hydric alcohol , glycerol and various fatty acid.
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Lipid and Lipid disorder.
Lipid classsification:

1. Simple lipid: (fatty acid with various alcohol)
a. Neutral fat
Fatty acid+Glycerol= TG
b. Wax
Fatty acid + High molecular wt alcohol

2.Compound Lipids:(Fatty acid +alcohol+others)

a. Phospholipids
Fatty acid+Glycerol+Phosphoric acid
b.Glycolipid
Lipid+CHO+Nitrogenous Base
c.Sulpholipid
Lipid+sulphergroup
d.lipoprotein
Lipid+Plasma protein

3. Derived lipid
Saturated and Unsaturated fatty acid
glycerol
sterol
vit A, Vit D

4.Miscelleneous Lipid.
Aliphatic hydrocarbon
carotinoid
Vit e, Vit K