Digestion and Absorption of Dietary Lipids

Table Of Contents

Major Dietary Lipids are:-
- TAGs: Tri Acyl Glycerol
- Cholesterol
- Phospholipids

Mouth/Stomach – Minimal digestion
Small Intestine- Major Digestion
Acidic chyme from stomach enters duodenum where emulsification of fat occurs by bile salts.
Dietary TAGs-
- Emulsified TAGs are hydrolysed by pancreatic lipase at 1 and 3 position to give 2 Mono Acyl Glycerols(MAG) and 2 Fatty Acids (FA)
- TAG + Lipase = 2 MAG + 2 FA
Cholesterol Esters-
- Enzyme: Cholesterol Ester Hydrolase (=Cholesterol Esterase)
- Cholesterol Ester + Cholesterol Esterase = Cholesterol +FA
Dietary Phospholipids-
- Enzyme: Pancreatic Phospholipase-A₂
- Hydrolysis at 2nd position of phospholipid
- Glycerophospholipid + Phospholipase A₂= Lysophospholipid + FA
Final Products-
- Free Fatty Acids (FFAs)
- Free Cholesterol
- 2 MAGs
- Lysophospholipid

End products + Bile Salts + fat soluble vitamins (ADEK) = Mixed micelles which approach the brush border intestinal mucosa.
Lipid component gets absorbed by simple diffusion
Absorbed lysophospholipid is reconverted to phospholipid
Absorbed cholesterol is reconverted to cholesterol esters
2 MAGs are reconverted to TAGs which then combines with just formed phospholipids and cholesterol esters to form chylomicrons