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Heterogenous group of Organic compounds,
Contains C, H, O and some times P and S
Esters of Fatty acids with alcohol
Insoluble in water
Soluble in organic solvents
SOURCES OF LIPIDS
Endogenous source: Lipids which are synthesized in body, Fatty acids, TAG, Cholesterol, Cholesterol esters, Phospho lipids
Exogenous Sources:Lipids obtained through diet,TAG – 90%, Phospholipids, CholesterolCholesterol esters, Free fatty acids,And Fat soluble vitamins – 10%
Exogenous sourcesof lipids
Animal source: Milk, Butter, Ghee, Meat, Egg yolk, Pork
Vegetable Sources:Oils from various oil seeds likeGround nut, Sunflower, Coconut, Mustered seed, Cotton seed
What is digestion?Complex lipid food molecules are
converted to simple and absorbable forms
• Requirements
• Place • Emulsifiers… Bile,
PL• Enzymes…….Lipases
• Difficulty• Hydrophobic
molecules in hydrophilic environment
• Solution• Emulsified,• increased surface
area, • made accessible for
Digestion in Mouth
Lingual Lipase
Ebner’s glandShort chain fatty acids
From TAG of milk
Short chain fatty acids+ Glycerol
Pediatric group important
Absorbed directlyinto blood stream
Digestion in the stomach
Churning of the food Brings emulsification Tri acyl glyceride having
medium chain FA hydrolysed
Action of lingual lipase continued
TAG → MAG + FA
DAGImportant in infantsdigestion of milk fat
Less important or not at all in adult
30% digestionTAG
ACTION OF ESTERASES
PANCREATIC ESTERASEFFA
CHOLESTEROL ESTERASES
TAG 2,3-DAG 2-MAG
1-MAG GLYCEROL FFA2-MAG
LIPASE LIPASE
ISOMERASE LIPASE
Action of pancreatic lipase on Tri acyl glycerolPlay major role
ColipaseBile acids
Olestra and orlistat powrful inhibitor of pancreatic lipase
End product of Triacyl glyceride digestion
Glycerol, Mono acyl glycerol,
Di acyl glycerol and
free fatty acids
Digestion of phospholipids
Enzymes --- Phospholipases
Four different types
Pancreatic ---Phopholipase A2
Product lysophospholipid
Action of EsterasesPancreatic origin
Cholesterol Ester
Cholesterol
Free fatty acid
Cholesterol esterase
Bile acids+
1. EMULSIFICATION
2. STABLISE THE EMULSION
3. PROVIDES ALKALINE MEDIUM
4. HELPS IN ABSORPTION
5. PRODUCE SURFACTANTS
6. POTENT CHOLERETICS
7. EXCRETES THE WASTE
8. SOLUBLISES THE CHOLESTEROL
STEATORRHEA
A clinical condition
Daily excretion of fat in feces is more than 6 gm per day.
CAUSES:
– Defective digestion of fat
– Defective absorption of fat
Defective Digestion - 1
• Bile duct obstruction
• Gall stone
• Emulsification defective
• Improper digestion
• Split fat in stool
Defective Digestion -2
• Disease of pancreas
• Pancreatitis
• Tumor- head of pancreas
• Partial or complete Pancreactomy
• Pancreatic juice block
• No lipase
• Unsplit fat in stool
• Normal
• Pancreatic lipase is found in high concentration in pancreatic secretions.
• It has high catalytic activity.
• BUT
• Cystic Fibrosis:
• Severe pancreatic lipase deficiency seen in cystic fibrosis results in malabsorption of lipids.
Bacterial infection
Prevent Fat Absorption and Obesity• Olestra:• Commercial lipid produced by esterification of
natural fatty acids with sucrose instead glycerol.
• 6 to 8 fatty acids are covalently coupled with sucrose
• They taste like lipid but not hydrolyzed to absorbable constituents and hence excreted.
• Orlistat:• Non hydrolysable analog of triacylglycerol.
• Powerful inhibitor of pancreatic lipase.
• Blocks lipid absorption and hence results in lipid excretion
• Chylothrorax
• Abnormal connection between pleural cavity and thoracic duct
• Leakage of lipid in pleural fluid
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