Cholesterol is a waxy substance found in your blood. Your body needs cholesterol to build healthy cells, but high levels of cholesterol can increase your risk of heart disease.

1. Cholesterol

2. Specific Learning objectives
At the end of the lecture students will be able to
• Define cholesterol.
• Explain the structure of cholesterol.
• Describe the properties of cholesterol.
• Explain the functions of cholesterol.
• Explain the compounds formed from cholesterol

3. Introduction
• The word cholesterol is derived from Greek words,
chole = bile; steros = solid; ol = alcohol.
• Exclusively found in animal & most abundant animal
sterol.
• Widely distributed in all cells & major component of
membranes and Lipoproteins.

4. Cont….
• Cholesterol comes from two sources
I. Body (specifically liver) –
Makes all the cholesterol we
need (about 700 mg of
cholesterol per day).
II. foods from animal origin
– such as cheese, egg yolks,
beef, pork, poultry, fish
(about 300 mg of
cholesterol per day).

5. Definition
Cholesterol is a structural component of cell
membranes and serves as a building block for
synthesizing various steroid hormones, vitamin D, and
bile acids.

9. Structure
• 27 carbon compound
• Double bond at C5-C6
• Hydroxyl group (OH group) at C3
• 8 carbon side chain at C17
• Total 5 methyl group
• molecular formula of C27H45OH.

11. Properties
• Yellowish crystalline solid
• Isolated cholesterol is a white, flaky
solid that is insoluble in aqueous
environments [Strongly hydrophobic]
• Soluble in organic solvent like
chloroform, benzene, ether etc.

12. Functions
• Cholesterol is essential to life.
• It is a structural component of cell membrane.
• Cholesterol is the precursor for the synthesis of all
other steroids in the body. These include steroid
hormones, vitamin D and bile acids.

13. Cont…
• Essential ingredient in structure of Lipoprotein.
• Transportation of fatty acid- . Fatty acids are
transported to liver as cholesteryl esters for
oxidation.
• Insulating cover for transmission of electric
impulse in nervous tissue.

14. I. Synthesis of bile acids
• The bile acids possess 24 carbon atoms, 2 or 3
hydroxyl groups in the steroid nucleus and a side
chain ending in carboxyl group.
• The bile acids are amphipathic in nature since they
possess both polar and non-polar groups.
• They serve as emulsifying agents in the intestine and
actively participate in the digestion and absorption of
lipids.
COMPUNDS FORMED FROM CHOLESTEROL

15. Cont….
• The synthesis of primary bile acids takes place in the
liver and involves a series of reactions.
• The step catalysed by 7 D-hydroxylase is inhibited by
bile acids and this is the rate limiting reaction.
• Cholic acid and chenodeoxycholic acid are the primary
bile acids and the former is found in the largest
amount in bile.

16. Cont….
• On conjugation with glycine or taurine, conjugated
bile acids (glycocholic acid, taurocholic acid etc.) are
formed which are more efficient in their function as
surfactants.
• In the bile, the conjugated bile acids exist as sodium
and potassium salts which are known as bile salts.

17. Cont….
• In the intestine, a portion of primary bile acids
undergoes deconjugation and dehydroxylation to form
secondary bile acids (deoxycholic acid and
lithocholic acid).
• These reactions are catalysed by bacterial enzymes
in the intestine.

18. Cholelithiasis
• Bile salts and phospholipids are responsible for
keeping the cholesterol in bile in a soluble state.
• Due to their deficiency (particularly bile salts),
cholesterol crystals precipitate in the gall bladder
often resulting in cholelithiasis—cholesterol gall
stone disease.
• Cholelithiasis may be due to defective absorption of
bile salts from the intestine, impairment in liver
function, obstruction of biliary tract etc.

19. II. Synthesis of steroid hormones from
cholesterol
Cholesterol is the precursor for the synthesis of all the
five classes of steroid hormones
(a) Glucocorticoids (e.g. cortisol)
(b) Mineralocorticoids (e.g. aldosterone)
(c) Progestins (e.g. progesterone)
(d) Androgens (e.g. testosterone)
(e) Estrogens (e.g. estradiol).

20. III. Synthesis of vitamin D
• 7-Dehydrocholesterol, an intermediate in the synthesis
of cholesterol, is converted to cholecalciferol (vitamin
D3) by ultraviolet rays in the skin.

21. Expected Questions
Short
• Explain the compounds formed from cholesterol.

22. THANK YOU
Eat good diet to
keep heart
Healthy