The Lipids: Triglycerides, Phospholipids and Sterols

1. The Lipids: Triglycerides, Phospholipids and Sterols

2. Lipids Objectives • 1. Understand the chemical composition and differences between fats • 2. Explain the structural and functional processes of triglycerides, phospholipids, and sterols • 3. Describe the process of fat digestion and absorption • 4. Discuss the different types of lipoproteins in the body • 5. Clarify the recommended intakes of fat and essential fatty acid requirements to meet daily nutritive needs • 6. Describe the health-risk factors with over consumption of lipids in the diet

3. TriacylglycerolTriglycerides R-COO-CH2 R-COO-CH R-COO-CH2 • Triglycerides found in seeds and • animal adipose. • Diglycerides found in plant leaves, • one fatty acid is replaced by sugar • (galactose).

4. Most Common Fatty Acids in Di- and Triglycerides CH3(CH2)nCOOH

5. Triglyceride Containing Linoleic Acid Omega-6

6. Linolenic Acid Omega-3

7. Fatty Acid Isomers

8. Fatty Acids • The Length of the Carbon Chain • long-chain, medium-chain, short-chain • The Degree of Unsaturation • saturated, unsaturated, monounsaturated, polyunsaturated • The Location of Double Bonds • omega-3 fatty acid, omega-6 fatty acid

9. Lipid Content of Feeds • Forages • Fat content is low: 1 to 4% of dry matter • High proportion of linolenic acid (18:3) • Diglycerides in fats of leaves • Grains • Fat content variable: 4 to 20% of dry matter • High proportion of linoleic acid (18:2) • Triglycerides in oils of seeds

10. The Length of the Carbon Chain Short-chain Fatty Acid (less than 6 carbons) Medium-chain Fatty Acid (6-10 carbons) Long-chain Fatty Acid (12 or more carbons)

11. Fatty Acids are Key Building Blocks • Saturated Fatty Acid • All single bonds between carbons

12. Monounsaturated Fatty Acid(MUFA) • One carbon-carbon double bond

13. Polyunsaturated Fatty Acid(PUFA) • More than one carbon-carbon double bond

14. Location of Double Bonds • PUFA are identified by position of the double bond nearest the methyl end (CH3) of the carbon chain; this is described as a omega number; • If PUFA has first double bond 3 carbons away from the methyl end=omega 3 FA • 6 carbons from methyl end=omega 6 FA

15. Degree of Unsaturation • Firmness • saturated vs. unsaturated • Stability • oxidation, antioxidants • Hydrogenation • advantages, disadvantages • Trans-Fatty Acids • from hydrogenation

16. Hydrogenation

17. Cis-fatty acid: H’s on same side of the double bond; fold into a U-like formation; naturally occurring; Trans-fatty acid: H’s on opposite side of double bond; more linear; occur in partially hydrogenated foods;

20. Essential Fatty Acids (EFA) • Omega-3: • Eicosopentaenoic acid (EPA) • Docosahexaenoic acid (DHA) • Alpha-linolenic acid (ALA) • flaxseed--most, canola (rapeseed), soybean, walnut, wheat germ • body can make some EPA and DHA from ALA • Omega-6 • corn, safflower, cottonseed, sesame, sunflower • Linoleic acid FISH

21. Omega-3 Omega-6

22. Omega-3 Fatty Acids • Associated with: • anti-inflammatory, antithrombotic, antiarrhythmic, hypolipidemic, vasodilatory properties • Inflammatory conditions • Ulcerative colitis, Crohn’s • Cardiovascular disease • Type 2 diabetes * Mental function • Renal disease * Growth and development

23. Essential Fatty Acid Deficiency • Classical symptoms include: • growth retardation, reproductive failure, skin lesions, kidney and liver disorders, subtle neurological and visual problems • People with chronic intestinal diseases • Depression--omega-3 • ?inadequate intake alters brain activity or depression alters fatty acid metabolism? • Attention Deficit Hyperactivity Disorder • lower levels of omega-3--more behavioral problems

24. Eicosanoids:made from EFA --derivatives of 20-carbon fatty acids; --affect cells where they are made; --have different effects in different cells --cause muscles to contract and muscles to relax; --help regulate blood pressure, blood clot formation, blood lipids, and immune response; --participate in immune response to injury and infection, producing fever, inflammation, and pain; --include:prostaglandins, thromboxanes, leukotrienes

25. Triglycerides • Structure • Glycerol + 3 fatty acids • Functions • Energy source • 9 kcals per gram • Form of stored energy in adipose tissue • Insulation and protection • Carrier of fat-soluble vitamins • Sensory properties in food

26. Triglycerides: lipids composed of three fatty acids attached to a glycerol

27. Triglycerides • Food sources • fats and oils • butter, margarine, meat, baked goods, snack foods, salad dressings, dairy products, nuts, seeds • Sources of omega-3 fatty acids • Soybean, canola, walnut, flaxseed oils • Salmon, tuna, mackerel • Sources of omega-6 fatty acids • Vegetable oils

28. Fatty Acids in Common Food Fats

29. Phospholipids • Structure • Glycerol + 2 fatty acids + phosphate group • Functions • Component of cell membranes • Lipid transport as part of lipoproteins • Emulsifiers • Phosphatidylcholine • Food sources • Egg yolks, liver, soybeans, peanuts

30. Cell membranes are phospholipid bilayers

31. Sterols: Cholesterol • Functions • Component of cell membranes • Precursor to other substances • Sterol hormones • Vitamin D • Bile acids • Synthesis • Made mainly in the liver • Food sources • Found only in animal foods