Nutrition.docx - Chapter 5 The Lipids Triglycerides...

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Chapter 5: The Lipids: Triglycerides, Phospholipids, and Sterols 1) Lipids a) Large and diverse group of substances. b) Insoluble in water. c) In foods, lipids occur as fats and oils . i) Fats (1) Butter, lard and things that are the same. They are solid at room temperature. ii) Oils (1) Olive oil. They are liquid at room temperature. d) Three types of lipids i) Triglycerides ii) Phospholipids iii) Sterols 2) Chemist’s View of Fatty Acids and Triglycerides a) Energy provided per gram greater than carbohydrates i) 9 kcal/gram b) Triglycerides – Glycerol and three fatty acids i) Most dietary lipids are triglycerides c) Fatty Acids – Even number of carbons i) Saturated or unsaturated d) Omega-3 and Omega-6 Fatty Acids i) 18-carbon polyunsaturated fatty acids 3) Triglycerides a) Three fatty acids attached to a glycerol. b) Formed via series of condensation reactions. i) *Making H20. The Glycerol has three O’s that condense with Hydroxyls from different fatty acids. c) Usually containing a mixture of fatty acids. i) Different lengths and different saturations. 4) Degree of Saturations in Fatty Acids a) Saturated – Full of hydrogen bonds. i) No double bonds ii) Stearic Acid iii) Tend to be solid (in room temperature) (1) Butter, lard, tallow, and other animal fats. (2) Tropical fats: coconut oil and palm oil. b) Unsaturated – missing hydrogens i) With double bonds ii) Polyunsaturated fats tend to be liquid at room temperature. (1) Vegetable oils, sunflower oils, etc. 5) Bonds in the Fatty Acid Chain a) Double bonds i) Nearest the methyl end of the carbon chain.
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b) Omega number represents location of the closest double bond from methyl end i) Oleic acid – One double bond ii) Omega-3’s closest double bond is three carbons away from methyl end. (1) Linolenic Acid (a) Can have up to 3 double bonds, as long as the closest carbon is three carbon atoms away from methyl end. iii) Omega-6’s closest double bond is six carbons away from methyl end. (1) Linoleic Acid (a) Can have up to 2 double bonds, as long as the closest carbon is six carbon atoms away from the methyl end. 6) Hydrogenation a) Protects against oxidation b) Makes liquid oils more solid i) Adds more hydrogen. c) Partial hydrogenation most common d) Trans -fatty acids i) Configurations – cis and trans ii) Relatively few natural sources of trans fat (1) Similarity to other types of fat 7) Phospholipids a) Solubility in fat and water b) Emulsifiers in food industry c) Sources i) Egg yolks, peanuts, and soybeans. d) Roles i) Part of cell membranes (1) Emulsifiers 8) Sterols a) Ring structure b) Sources i) Cholesterol (1) Animal-based food ii) Plant sterols c) Roles i) Made in the body ii) Structural component of cell membranes 9) Lipid Digestion a) Fats are hydrophobic i) Digestive enzymes are hydrophilic (1) Hydrophobic: water-avoiding (2) Hydrophilic: water-attracting b) Goal of fat digestion i) Dismantle triglycerides into Monoglycerides (fatty acid + glycerol) 10) Fat Digestion
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a) Beginning i) Mouth (1) Lingual lipase plays role in fat digestion in infants ii) Stomach (1) It is mixed and broken into droplets (2) Gastric lipase (a)
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  • Spring '08
  • RazSaadat
  • Incomplete, Chapters 5 -10

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