18 Lipids - Digestion and Absorption

18 Lipids - Digestion and Absorption - Lipids: Digestion...

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Lipids: Digestion and Absorption HNFE 3025 Fall 2009
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Lipid Dietary Intake According to 1999-2000 NHANES report,  American men take in almost 100 g of  dietary fat and women about 70 g daily.   This represents ~33% of daily caloric  intake AHA recommends no more than 30% of  fat in diet Ratio of dietary  ω 6/  ω 3 roughly 10:1  Dietary fat is overwhelmingly TAG, PL (1-2  g), Cholesterol and Cholesterol esters  (300-350 mg) plus fat soluble vitamins (A,  D, E, K) 2
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Terms to Know Amphipathic : refers to a molecule or structure with  both hydrophobic and hydrophilic parts  (phosphatidyl choline) Emulsion : suspension of tiny lipid particles in an  aqueous solution – usually stabilized by  amphipathic substance(s) Emulsifier  (surfactant) is something that stabilizes  an emulsion. Micelle : an aggregation of amphipathic  substances in an aqueous solution, in which the  hydrophilic parts extend toward the aqueous  phase and the hydrophobic parts point toward the  interior. 3
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Lipid Digestion PROBLEM!: lipids are hydrophobic being digested in a hydrophilic environment Emulsification: a process that allows for increased surface area of dietary lipid targeted for digestion Increases accessibility of fat to digestive enzymes Bile salts are of major importance 4
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Emulsification 5 A. Two immiscible liquids (not  emulsified) A. An emulsion of Phase B dispersed  in Phase A A. The unstable emulsion progressively  separates A. The emulsifier (surfactant) (purple  outline) positions itself on the  interfaces between Phase A and  Phase B, stabilizing the emulsion
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Digestion in the Mouth Lingual lipase Secreted from the serous gland beneath the tongue Lipase cleaves the ester bond at the carbon 3 position (a.k.a., sn 3) Digestive products include 1,2-diacylglycerol and fatty acids Minor contribution 6
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18 Lipids - Digestion and Absorption - Lipids: Digestion...

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