VPB 112: General Veterinary Biochemistry (1+1)

CHOLESTEROL

• Cholesterol has steroid nucleus (cyclopentanoperhydrophenanthrene).
• The molecule contains 27 carbon atoms. There is one double bond between carbon atom 5 and 6 and a hydroxyl group at position 3. A branch consisting of 8-carbon unit is attached to the D –ring at position 17. Two methyl groups are attached at positions 10 and 13, constituting carbon atom 19 and 18 respectively.
• It occurs in animal fats but not in plant fats.
• Cholesterol is amphipathic with a polar head group (hydroxyl group at C3) and a non-polar hydrocarbon body.
• Much of the plasma cholesterol is in an esterified form, with a fatty acid attached at C3, which makes the structure more hydrophobic.

Importance of cholesterol

• It is a constituent of membrane.
• It is the precursor of bile acids, steroid hormones and vitamin D.
• It is a component of lipoproteins.
• It is a poor conductor of heat, hence acts as an insulating material.