ESTERIFICATION OF LIPIDS. MICELLES ENZYMES REQURIED

1. DIGESTION &ABSORPTION
OF
LIPIDS

2. • Dietary lipids – derived from plants
and animals.
• Essential for growth and
development.
• They are oxidized for energy or
stored as reserve fat in adipose
tissue.

3. FFA, 3%PL 5%cholesterol, 2%
TAG, 90%
Dietary Lipid contents
Triacylglycerols Cholesterol Phospholipid FreeFattyAcid
•Adult ingest about 60-150g of lipids per day.
• >90% of fat intake is as triacylglycerols.

4. DIGESTION
OF LIPIDS
• Lipid molecules are not soluble in
aqueous solution.
• Enzymes are soluble in aqueous
medium.
• Digestion of lipid presents a problem.
• This problem is solved by
emulsification of lipids by bile salts.

5.  Lingual lipase- secreted by dorsal
surface of tongue.
 But this enzyme is not significant in
humans.
 Little or no digestion of lipids occur
in mouth.

6. Gastric lipase secreted by stomach.
Hydrolyses TAG molecules,
especially short & medium chain
fatty acids.
In adults, stomach pH is acidic,
dietary lipids are not digested in
stomach.
Lipids requires neutral pH for
digestion.

7. •Acidic chyme containing dietary fat
contents passes from stomach to
duodenum.
•Stimulates the secretion of 
1.Cholecytokinin (CCK)
2.Secretin

8. Act on pancreas
release
bicarbonate
CHOLECYTOKININSECRETIN
Acts on gallbladder
 release bile
Acts on pancrease
 release pancreatic
enzymes

9. Major function
of bile
Isto provide emulsifying
agents:
•Bile salts
•Phosphtidylcholine

11. ACTION OF PANCREACTIC ENZYMES ON
DIETARY LIPIDS IN SMALL INTESTINE
PANCREATIC LIPASE
CHOLESTEROL
ESTERASE
PHOSPHOLIPASE –A2

12. HYDROLYSIS OF DIETARY TAG
Emulsification of Triacylglycerols – pancreatic
lipase.
Lipase acts on 1 & 3 position of TAG.
End product of Triacylglyceride digestion-
1.2-Monoacyl glycerol,
2.Glycerol,
3.Free fatty acids

13. OH
OH
OH
OH
OH
OH
Triacylglycerol (TAG) Diacylglycerol(DAG)
2-Monoacylglycerol
(2-MAG)
Glycerol
Fatty acidH20
Fatty acid
H20
H20 Fatty acid
HYDROLYSIS OF DIETARY TAG

14. HYDROLYSIS
OF DIETARY
PHOSPOLIPIDS

15. HYDROLYSIS OF CHOLESTEROL ESTER

16. (Small amount)

19. Micelles reaches brush border of
intestinal mucosal cells.
Lipids compounds from micelles
pass through mucosal cells and
are absorbed.
Site of absorption – jejunum &
ileum.

23. Of Bile Salts

26. STEATORRHEA-
A clinical condition
Daily excretion of fat in feces is >6 gm
per day.
CAUSES:
– Defective digestion of fat
– Defective absorption of fat

27. • Bile duct obstruction
due to Gall stone
• Emulsification defective
• Improper digestion
DEFECTIVE DIGESTION- 1

28. Disease of pancreas-
• Pancreatitis
• Tumor- of pancreas
• Partial or complete
pancreactomy
• Pancreatic juice blockage
• Absence of pancreatic lipase
• Unsplit fat in stool
DEFECTIVE DIGESTION- 2

29. DEFECTIVE ABSORPTION
Cystic Fibrosis:
• Genetic disorder
• Production of mucus i.e.,
thick & sticky.
• Severe pancreatic
lipase deficiency seen
in Cystic fibrosis results
in malabsorption of
lipids.

30. THANK YOU