Lipid Digestion 122809 wo pics 2sld

Lipid Digestion 122809 wo pics 2sld - LIPID DIGESTION &...

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1 L IPID D IGESTION & A BSORPTION ( PG . 140-147) Lia M. Nightingale, Ph.D. L IPIDS IN O UR D IET Mainly TGs (~95%) Remaining 5%: Sterols (mainly cholesterol) Mostly as free cholesterol 10-15% are cholesterol esters Phospholipids Sterols & phospholipids TG
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2 C HOLESTEROL E STERS O 3 C = O Fatty acid L IPID D IGESTION - M OUTH Lingual lipase released in mouth Activity decreases with age Most active in infants CH 2 – O – C – R 1 R 2 – C – O – CH CH 2 – O – C – R 3 O O O sn-1 sn-2 sn-3 Removes sn-3 FA on TG containing short or medium chain FA Products of lingual lipase digestion: 1,2 DG & FA
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3 L IPID D IGESTION - S TOMACH Lipids are nonpolar need to be emulsified in order to allow digestion in stomach Shear of stomach churning helps mix Polysaccharides, phospholipids, digested proteins in chyme act as emulsifiers By which part of the stomach? L IPID D IGESTION - S TOMACH Gastric lipase released in stomach Together lingual lipase & gastric lipase digest ~20% of TG CH 2 – O – C – R 1 R 2 – C – O – CH CH 2 – O – C – R 3 O O O sn-1 sn-2 sn-3 Removes sn-3 FA on TG containing short or medium chain FA Products of gastric lipase digestion: By which cells??
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4 L IPID D IGESTION - S TOMACH Presence of fat in stomach causes release of hormones that decrease gastric motility (gastric emptying) : CCK GIP GLP-1 Lipids have a high satiety value L IPID D IGESTION - SI Chyme enters SI releasing: CCK Contracts pancreas Contracts gallbladder Secretin Contracts pancreas What is released? What is released? What is released?
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5 Made in liver from cholesterol Stored in the gallbladder B ILE A CIDS HO OH OH COO - Cholic acid (cholate ) C ONJUGATED B ILE A CIDS Bile acid + glycine C – N – CH 2 COO - Glycocholate O H glycine HO OH OH
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6 C ONJUGATED B ILE A CIDS Bile acid + taurine C – N – CH 2 CH 2 SO 3 - Taurocholate H taurine O HO OH OH B ILE A CIDS ILE S ALTS Large lipid droplet Bile acids from gallbladder
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7 L IPID D IGESTION Micelles = fatty acids, monoglycerides, fat- soluble vitamins, B R U S H B O R D E R Unstirred water layer (UWL) P ANCREATIC Z YMOGENS Colipase, Bile, Ca 2+ Trypsin Trypsin Procolipase Colipase Pancreatic lipase Active pancreatic lipase Prophospholipase A 2 Phospholipase A 2 Esterase Pancreatic lipases digest ~80% of TG ?
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