Ch. 20 Lipids

1. Ch. 20Lipids Milbank High School

2. Objectives • 1.How are lipids defined? How are they classified? • 2.What is a fatty acid? What is the difference between a saturated, monounsaturated, and polyunsaturated fatty acid? • 3.Why are fats and oils referred to as triglycerides (or triacylglycerols)? What determines if a triglyceride is a fat or oil? • 4.What does the iodine number tell you about a triglyceride? • 5.Why is it important for a soap to have both a hydrophilic and a hydrophobic end?

3. Objectives • 6.What are the functions of phospholipids, glycolipids, and sphingolipids? What distinguishing characteristics are used to place lipids into one of these categories? • 7.What are the major components of cell membranes and how are they arranged? • 8.What are the functions of steroids? • 9.What is the link between cholesterol, lipoproteins, and cardiovascular disease?

4. Lipids • Fats and oils • Twice the energy as carbs…but it usually goes into storage • Uses other than energy: • Protection • Cell membranes • Fat soluble vitamins A, D, E, and K

5. Lipids • Classified as a group based upon their solubility • INSOLUBLE in water • Lipid: compound isolated from body tissues that is more soluble in organic solvents than in water • Broad variations in structure

6. Sec. 20.1Fatty Acids • Carboxylic acids • Components of fats and oils • Even number of carbon atoms • Saturated fatty acids • Monounsaturated fatty acids • Polyunsaturated fatty acids

7. Fatty acids Con’t • Use table 20.1 to answer the following questions: • Find an example of a: • Saturated fatty acid • Polyunsaturated fatty acid • Monounsaturated fatty acid • Draw • Myristic acid • Oleic acid • Linoleic acid

8. Sec. 20.2Fats and Oils • Most abundant lipids in nature • Energy, protection, insulators • “Triglycerides” • Esters composed of three fatty acids joined to glycerol, a trihydroxy alcohol • Fats if solid at 25°C • Oils if liquid at same temp

10. Fats and Oils Con’t • Saturated fats • Cholesterol • Arteriosclerosis • Use olive oil or canola oil • They lower LDL cholesterol • High percentage of monounsaturated fatty acids

11. Reactions of Fats and Oils • Hydrolysis • Hydrogenation • Oxidation • Antioxidants

12. Sec. 20.3Soaps • Saponification • Second oldest organic synthesis (1st is production of ethyl alcohol) • Hydrolysis of triglycerides + sodium carbonate

13. How do soaps work? • Figure 20.4 • Hydrophilic (water soluble) • Hydrophobic (repelled by water) • Soaps don’t work well in hard water (soap scum) • Detergent • Toothpaste!?!

14. Sec. 20.4Membrane Lipids • Phospholipids • Phosphoglycerides • Glycolipids • Sphingolipids • Sphingomylelins • Cerebrosides • Gangliosides

15. Sec. 20.5Cell Membranes • Cytoplasm • Micelles • Bilayers • Three major classes in the membrane bilayer of animal cells: • Phospholipids • Glycolipids • Cholesterol

16. Cell Membranes • Two rows of phospholipid molecules • Tail to tail • Semipermeable • Integral proteins • Peripheral Proteins

17. Sec. 20.6Steroids: Cholesterol and Bile Salts • Nonsaponifiable • Bile salts, cholesterol, cortisone (hormone), sex hormones, and related compounds • Must have 4 fused rings

18. Cholesterol • Does not occur in plants • Most abundant steroid in human body • Biosynthesis of: • Sex hormones • Adrenal hormones • Vitamin D • Excess cholesterol • Gall stones

19. Bile • Produced in liver • Bile salts • Aid in the digestion of dietary lipids • Aid in absorption of fatty acids, cholesterol, and fat-soluble vitamins • Effective detergents and emulsifying agents

20. Sec. 20.7 Cholesterol and Cardiovascular Disease • Primary factor in atherosclerosis, coronary artery disease, and stroke • 41.5% of deaths nationwide • High cholesterol (over 260mg/100mL) • Males higher than females

21. Cholesterol • Not soluble in water • Cannot be transported in blood unless linked with a lipoprotein (water-soluble proteins) • 4 types • Chylomicrons • Very low density (VLDL) • Low-density proteins (LDL) • High-density proteins (HDL) • Contains least amount of lipid

22. Cholesterol • High levels of LDL increase heart disease risk • High HDL reduces heart risk • LDL:HDL ratio better indicator of heart disease risk

23. HDL • Transport excess cholesterol from various tissues to the liver where it is metabolized • Basically they are removing cholesterol from the blood • Increase HDL by: • Exercise • Lose weight • Alcohol in moderation

24. Dietary Modifications • Average American: 600 mg/day of cholesterol • Recommended: 300 mg/day • One large egg: 215 mg • Integrate unsaturated fat for saturated fats • Omega-3 fatty acids • Fish oil • Reason? • Polyunsaturated fatty acids

25. Atherosclerosis • Most common form of arteriosclerosis (thickening of the arterial walls) • LDL’s lodge in arteries, oxidized, white blood cells try to consume oxidized products, enlarged white blood cells accumulate, causes plaque that narrows arteries • Most serious consequence: heart attack

26. Statins • Inhibits the enzyme HMG-CoA reductase • Inhibition of this enzyme in the liver stimulates LDL receptors, resulting in an increased clearance of low-density lipoprotein (LDL) from the bloodstream and a decrease in blood cholesterol levels. • Lipitor, Crestor

27. Olestra • Fat substitute, calorie free • Synthesized using a sucrose molecole, which holds many fatty acids chains • Molecule is too large to move through intestinal wall • Olean • May cause cramps and diarrhea

28. Heart Healthy Foods • Top 25—see article • Phytoestrogens • Flaxseed • Phytosterols • Carotenoids • Polyphenols • Omega-3 fatty acids • B-Complex vitamins

29. Leptin • Regulates energy intake and enery expenditure • Appetite and metabolism • Regulated downward at night by melatonin • Increased during pregnancy