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Lipids: An Explanation of Digestion, Absorption and Function in the Body

Lipids: An Explanation of Digestion, Absorption and Function in the Body. By Jillian Butt. Objectives. Identify and explain types of lipids Discuss consumption and storage of lipids in the United States Explain complete digestion of lipids including re-esterification

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Lipids: An Explanation of Digestion, Absorption and Function in the Body

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  1. Lipids: An Explanation of Digestion, Absorption and Function in the Body By Jillian Butt

  2. Objectives Identify and explain types of lipids Discuss consumption and storage of lipids in the United States Explain complete digestion of lipids including re-esterification Describe absorption of lipids Explain lipid deposition and mobilization

  3. Types of Lipids Fatty Acids Triglycerides Phospholipids Cholesterol Bile Acids

  4. Fatty Acids • Molecular content 4 to 22 carbons per chain • Saturated or unsaturated chains • Cis or trans configuration • Function dependent on shape • Linoleic and alpha-linolenic acids

  5. Triglycerides • Esters of fatty acids and glycerol • Saturation dependent on function • Storage form of energy in the body

  6. Phospholipids • Esters of glycerol, two fatty acids, and a phosphate group • Can be free or esterified • Charged molecules • Integral in membranes • Lysophospholipid when one fatty acid is missing

  7. Cholesterol • Steroid structure with a hydroxyl group • Parent compound for bile synthesis • Can be recycled in body or synthesized • Can lead to atherosclerosis

  8. Bile Acids • Steroid acids made from cholesterol • Found primarily in the small intestine • Emulsify fats • Allow movement of lipids in aqueous solution

  9. American Consumption of Lipids Triglycerides largest fraction of diet Phospholipids eaten in egg yolks Cholesterol likely to be 1 g per day Fat soluble vitamins ingested in small amounts

  10. Storage of Lipids in the Body About 166,000 kilocalories of energy storage Mostly lipids as triglycerides 98% in adipose tissue depots Small fraction in cell membranes Depots located in subcutaneous blood vessels, abdominal cavity, and area around thighs and buttocks

  11. Digestion of Lipids Minimal in oral cavity Gastric lipase secreted in stomach Emulsification of lipids in small intestine Four secretions in small intestine Overall four products of digestion

  12. Esterification of Products of Digestion Limited solubility in body Micelles formed to move products to enterocyte Re-esterified in enterocyte to enter body

  13. Absorption of Lipids • Lipoproteins formed to transport lipids around body • Apoproteins necessary to become mature lipoprotein • Lipids moved into lacteals to venous circulation • Lipoprotein Lipase used to absorb lipids into tissues • Remnant moved to liver

  14. Fat Deposition Excess energy stored as fat Adipocytes used to hold one single fat droplet Mobilized when fasting or in between meals

  15. Fat Mobilization • Triglycerides broken down to glycerol and fatty acids • Hormone sensitive lipase and monoacyl glycerol hydrolase used in disassembly • Fatty acid transferred into mitochondria • Energy created through beta oxidation

  16. Questions?

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