Cholesterol Structure

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Cholesterol is a fat soluble white crystalline sterol or steroid alcohol C27H45OH.It has a 17 carbon nucleus of
four fused hydrocarbon rings (3 hexane,one pentane;cyclopentano-perhydrophenanthrene).It bears hydroxyl
group at carbon 3,two methyl groups (carbon-18 and carbon-19) at carbon position 10 and 13.An eight
carbon side chain is attached at carbon-17.Cholestrol is found exclusively in animal food especially
meat,animal fat and egg yolk.

The major part of body cholesterol is synthesized in liver and adrenal cortex.Other organs taking part in
synthesis of cholesterol are skin,intestine,kidneys,ovaries and testes.Synthesis is regulated by ingested
cholesterol.Digestion of cholesterol is dependent upon enzyme cholesterol esterase present in pancreatic
juice.Absorption is mediated through bile.Normal cholesterol concentration of blood is 140-250mg/100ml.

Cholesterol occurs both in free  state as well as combined with fatty acids as its hydroxyl group of carbon 3.It
also forms component of low density lipoproteins, very low density lipoprotein and high density lipoproteins.

Importance of Cholesterol:

1. Cholesterol is component of cell membranes in animals and wall-less bacteria called mycoplasma.

2. It helps in formation of bile salts and bile acids.

3. Cholesterol prevents premature breakdown of erythrocytes.

4. It forms Vitamin D near the surface of irradiated skin.

5. It promotes absorption of fatty acids.

6. It transports fat to liver for metabolism.

7. It forms steroid hormones in the adrenal glands. It produces sex hormones.

8. It produces sex hormones.

9. Moulting hormone ecdysone is formed from cholesterol

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