lipid

1. DIGESTION &
ABSORPTIONOF LIPIDS
6/18/2023 7:04 PM

2. DIETARY
LIPIDS
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.
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3. DIETARY
LIPIDS
TRIGLCERIDES
PHOSPH
OLIPID
FFA
CHOLESTEROL
ESTER
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4. DIGESTION
OF LIPIDS
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5. DIGESTION
OF LIPIDS
IN MOUTH
Lingual lipase – secreted by dorsal
surface of the tongue
But this enzyme is not significant in
humans
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LITTLE OR NO DIGESTION OF LIPIDS IN MOUTH

6. DIGESTION
OF LIPIDS
IN
STOMACH
Lipids delay the rate of emptying the
stomach by ENTEROGASTRONE
 Inhibits gastric motility
Retards discharge of food from
stomach
FATS HAVE SATIETYVALUE
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7. DIGESTION
OF LIPIDS
IN
STOMACH
Heat of the stomach –liquidising dietary
lipids
Peristaltic movements of the stomach –
emulsification of lipids
Gastric lipase and lingual lipase
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8. DIGESTION
OF LIPIDS
IN
STOMACH
Both enzymes are relatively acid-stable
Play a particularly important role in
 lipid digestion in neonates
in individuals with pancreatic
insufficiency - cystic fibrosis
Hydrolyses TAG molecules especially
those with short- to medium-chain
fatty acids
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GASTRIC LIPASE AND LINGUAL LIPASE - “ACID LIPASES”

9. DIGESTION
OF LIPIDS
IN SMALL
INTESTINE
ACIDIC CHYME
STIMULATES DUDENAL
MUCOSATO RELEASE
• SECTRETIN
• CHOLECYSTOKININ
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10. DIGESTION
OF LIPIDS
IN SMALL
INTESTINE
SECRETIN
Stimulates
pancreas to release
bicarbonate &
pancreatic juice
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11. DIGESTION
OF LIPIDS
IN SMALL
INTESTINE
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GALL BLADDER
BILE
PANCREAS
LIPASE
PANCREAS
PHOSPHOLIPASE
A2
PANCREAS
CHOLESTEROL
ESTERASE
CCK

12. DIGESTION
OF LIPIDS
IN SMALL
INTESTINE
The major
function of bile
Is to provide
emulsifying agents:
Bile salts &
Phosphtidylcholine
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13. DIGESTION
OF LIPIDS
IN SMALL
INTESTINE
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Hydrolysis of
dietaryTG
Hydrolysis
of dietary
PL
Hydrolysis
of
Cholesterol
Ester

14. HYDROLYSIS
OF DIETARY
TG
OH
OH
OH
OH
OH
OH
Triacylglycerol (TAG)
Diacylglycerol (DAG)
Monoacylglycerol
(MAG)
Glycerol

15. HYDROLYSIS
OF DIETARY
PL
by
Phospholipase
–A2
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16. HYDROLYSIS
OF
CHOLESTEROL
ESTER
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17. PRODUCTS
OF LIPID
DIGESTION
2-MAG
FFA
CHOLESTEROL
LYSO PL
1-MAG
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18. ABSORPTION
OF LIPIDS
 The products of digestion are incorporated into
molecular aggregates to form mixed micelle
 Micellar formation is essential for the
absorption of fat soluble vitamins A, D, E and K
 Site of absorption is jejunal mucosa
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19. MIXED
MICELLES
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2-MAG
FFA
CHOLESTE
ROL
LYSO PL
1-MAG
Vita
min
A,D
,E,K

20. ABSORPTION
OF LIPIDS BY
INTESTINAL
MUCOSAL
CELLS
6/18/2023 7:04 PM
2-MAG
FA
C
LysoPL
Vitamin
A,D,E,K
2-MAG
FA
C
LysoPL
Vitamin
A,D,E,K
CoA-SH
Fatty acyl-CoA
TG
CE
PL
Vitamin
A,D,E,K
APOLIPOPROTEIN
B-48
Free CHOLASTEROL
MIXED
MICELLES

21. ABSORPTION
OF LIPIDS
 CHYLOMICRONS
from intestinal
mucosal cells are
absorbed into
lymphatic system
then into systemic
circulation via
thoracic duct
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22. ABSORPTION
OFSHORT &
MEDIUM
CHAIN FATTY
ACIDS
 Short and medium chain fatty acids do not
need re-estrification
 They can directly enter into blood vessels
 So they are better absorbed than long chain
fatty acids
6/18/2023 7:04 PM

23. ENTEROHEPA
TIC
CIRCULATION
OF BILESALTS
Bile salts are reabsorbed from ileum and
returned to the liver to be re-excreted
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24. LIPID
DIGESTION &
ABSORPTION
6/18/2023 7:04 PM

25. ABNORMALIT
IES : LIPID
MALABSORPT
ION
Steatorrhea
Bile salt
deficiency
Pancreatic
enzyme
deficiency
Congenital
abetalipoproteine
mia
6/18/2023 7:04 PM