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Biochemistry
stage
nd
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Dr.Lamees Majid Al-Janabi
LIPID METABOLOSIM
Brief review about lipid chemistry:
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Fatty Acids
structure
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- Cholesterol
Normal serum cholesterol < 200 mg/dl
We have two types of cholesterol :
1) Endogenous: greater of the body cholesterol is provided
by synthesis of about 700 mg/day ( MORE THAN HALF )
2) Exogenous: daily intake of the cholesterol usually less
than 1g/day of which 40-70 % is absorbed.
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Uses:
One of the main compound of the cell membrane. Precursor in the steroid
hormones ,bile acids ,vitamin D synthesis .(The body can't break the steroid
nucleus ,body can eliminate cholesterol either as unchanged or converted
to bile acids ).
Triglyceride
Normal serum TG concentration is<150 mg\dl .
Uses: energy store
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Sources:
1) Exogenous:
main component of the diet ,daily intake is between 100-
200 g, by the action of pancreatic Lipase will be hydrolyzed to
monoglycerides and 2 fatty acid, these will be absorbed and the TG
resynthesised in the mucosal cell and incorporated in structure called
"Chylomicron" and release into intestinal lymph and reach systemic
circulation through thoracic duct .
2) Endogenous:
the liver is the major site for synthesis from glycerol and
fatty acid which incorporated into Lipoproteins and release into the
circulation to utilized by peripheral tissue as energy source or stored in
adipose tissue.TG that are carried by Lipoprotein and stored by adipose
tissue can't be utilized without prior hydrolysis to glycerol and fatty acid.
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- Phospholipids
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Serum level: 120-390 mg/dl
mainly synthesized in the liver and small intestine ,it's amphipathic
molecule (contain polar and non polar portion) and consequently ideally
suited as main component of the cell membrane.
PL have specialized function e.g.
*Lecithin is the major component of lung surfactant.
* Also inositol PL in cell membrane act as a precursor of hormone second
messenger
-Free Fatty Acids
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normal range 6-16 mg\dl .
Mainly derived from daily TG, but the body is able to synthesis most of
the fatty acids except essential fatty acids(poly unsaturated F.A.).F.A. is an
alteration energy source of glucose. Polyunsaturated F.As. is substrate for
prostaglandin.