Chapter 21 Lipids

1. Chapter 21 Lipids Biological chemicals that are insoluble in water (fat soluble, oily, oil soluble, mainly nonpolar) (hydrophobic- water hating) = FAT ? Only part of lipids are fats but sometimes we generalize and call some lipid systems “fatty systems” even though there may be no fat involved

2. As a Society we are worriedabout fats and try to eliminate by any means including surgery. • Fats and oils have gotten a bad reputation They are necessary for life • In fact some of our desire to get away from “bad fat” • may get us eventually a worse problem….. later

3. Lipids Lipids:a heterogeneous class of naturally occurring organic compounds classified together on the basis of common solubility properties. insoluble in water, but soluble in organic solvents including diethyl ether, dichloromethane, and acetone Lipids include: fatty acids, triglycerides, sphingolipids, phosphoacylglycerols, and glycolipids. lipid-soluble vitamins. prostaglandins, leukotrienes, and thromboxanes. cholesterol, steroid hormones, and bile acids.

4. Waxes and oils are necessary They protect us from outside chemicals, like a leaf does, to keep bad things out and moisture in. A thin layer of oil over the water in your eye keeps the water from evaporating and makes it easy to open and close your eyes. That is why soap in the eye hurts so much because it breaks up the oil and makes the movement rough.

5. Fats are necessary for Life Penguins, fish and us need the fats and oils • to insulate, • to protect nerve fibers, • to make the very cell membranes that make the cells that make us, • to store energy. We will try to separate the hype from the facts to help us better understand lipids.

6. Lots of other nonpolar stuff These are esters Lipid A biological compound that is soluble only in nonpolar solvents.

7. Lipids Overview Lipids Lipid Structures Fatty Acids Saponifiable Lipids Non-Saponifiable Lipids Lots of others Simple Lipids Complex Lipids Cholesterol Waxes Triglycerides Phosphoglycerides Sphingolipids Eicosonoids Steroids single ester triesterenergy storage (9 Cal/g)FA storage Cell membranes Cell membranes Hormones (local) Cell membraneshormones(global)hormones(local)

8. Messengers esters Lipid A biological compound that is soluble only in nonpolar solvents. cholesterol Singleester triester Also an energy storage (9 Cal/g)

9. Fatty Acids Building blocks of many lipids Long chain carboxylic acids (fatty acids)

10. Usually straight chains (no branching) • Sizes usually range for C10 to C20 • Usually have an even number of carbons • Can be saturated (no C=C bonds) or unsaturated (has C=C bonds) • Unsaturated Fatty acids in nature mostly have cis double bonds (kinks to make non linear) trans are in very small amounts. Fatty Acids – common characteristics

11. Fatty Acids, cont. In water, fatty acids will form micelles.

12. 14:0 16:0 18:0 20:0 w-7 16:1 w-9 18:1 w-6 18:2 w-3 18:3 w-6 AA 20:4 w-3 IPA 20:5 DHA 22:6

13. Fatty Acid – molecular shapes C=C causes “kinking” of the carbon chain

14. Straight Chain and cis-Double Bonds in Fatty Acids

15. Fatty Acids – molecular shapes, cont. All natural fatty acids with double bonds are cis Fatty acids with Cis-C=C bonds cannot pack closely together because of shape. This leads to decreased intermolecular attractions and lower melting points. NOTE: Trans fatty acids (not natural) are linear Fatty acid melting points decrease as the number of cis-C=C bonds increases. Most unsaturated fatty acids are liquids at room temperature.

16. Essential Fatty Acids Those needed by the body, but not synthesized within the body in adequate amounts. For humans, linoleic and linolenic acid are essential, but easily obtainable from plant and fish oils.

17. Structure of Fats and Oils Fats Usually from animal sources. Are solids at room temperature. Contain a high degree of saturated fatty acids. Oils Usually from plant and fish sources. Are liquids at room temperature. Contain more unsaturated fatty acids. Fats (or oils) store 9 Calories per gram – slow releasecarbohydrates store 4 Calories per gram – faster release Alkanes – poly alcohols – carbon dioxide (fats) (carbohydrates) Most energy – Least Energy

18. Triglycerides Physical properties depend on the fatty acid components: Melting points of fatty acids increases as the number of carbons in the hydrocarbon chains increases and as the number of double bonds decreases. Triglycerides rich in unsaturated fatty acids are generally liquid at room temperature and are called oils Triglycerides rich in saturated fatty acids are generally semisolids or solids at room temperature and are called fats.

19. Triglycerides The lower melting points of triglycerides rich in unsaturated fatty acids are related to differences in their three-dimensional shape. Hydrocarbon chains of saturated fatty acids can lie parallel with strong London dispersion forces between their chains; they pack into well-ordered, compact crystalline forms and melt above room temperature Because of the cis configuration of the double bonds in unsaturated fatty acids, their hydrocarbon chains have a less ordered structure and London dispersion forces between them are weaker; these triglycerides have melting points below room temperature.

20. Structure, cont. Fats and oils are triglycerides (triglycerols) which are triesters of glycerol.

21. Alcohol + Acids  Esters + Water Structure, cont. An example of the esterification process.

22. Fats and oils are a mixture of fatty acids made into triesters. Many times the fat molecule may be made from three different fatty acids. Each organism has its own mixture of the SAME fatty acids. The specific ratio of fatty acids also depends on the type of cell it is in. The above graphic is for the stored fats and oils. Fig. 18-7, p.571

23. Fig. 18-8, p.571

24. Fig. 18-9, p.574

25. Glycerol + fatty acids (triester) Less double bonds Called saponification -makes micelles in water Raise the melting point p.575

26. Reactions of Fats and Oils Hydrolysis – important for fat and oil digestion. A stored fat or oil

27. Reactions, cont. Saponification – the commercial production of the salts of fatty acids (soaps).

28. Hydrogenetion(adding H2) Hardening: reduction of some or all of the carbon-carbon double bonds of an unsaturated triglyceride using H2/transition metal catalyst. In practice, the degree of hardening is carefully controlled to produce fats of a desired consistency. The resulting fats are sold for kitchen use (Crisco, Spry, Dexo, and others). Margarine and other butter substitutes are produced by partial hydrogenation of polyunsaturated oils derived from corn, cottonseed, peanut, and soybean oils.

29. Reactions, cont. Hydrogenation – decreases the degree of unsaturation(gets rid of double bonds) Used to make margarines from oils. (ie. Makes the “fats harder”) The catalyst in this process can also isomerize some cis-double bonds to trans-double bonds not usually found in nature trans fatty acidsThese are found in stick margerine, shortning, high fat baked goods Studies suggest that cholesterol may increase with trans-fatty acids

30. Example of productclaiming “0” trans fat (it actually has just less than 0.5g trans fat/serving“Smart Balance” has 0.09g/serving)

31. A margarine Ingredient list Water, Vegetable oil blend (liquid Soybean oil, partially hydrogenated soybean oil), Sweet Cream Buttermilk, salt, gelatin, vegetable mono and diglycerides, soy lecithin, potassium sorbate, calcium sodium EDTA used to protect quality, lactic acid, artificial flavor, vitamin A palmitate, Beta carotene (for color) Sweet Cream Buttermilk(liquid formed above sweet cream butter)Approximate Laboratory Analysis (as powder, no water)Butterfat 7.0% (melts body temp)Crude Protein (6.38) 32-34% Minerals 8.0%Moisture 3.5%Lactose 48%www.ramsendairy.com/prod9.htm Potasium sorbate(inhibits mold, bacteria) Vitamin A palmitate(from palmitic acid and retinol)

32. A John Hopkins Study • Trans fats are probably the unhealthiest fats in the American diet. They not only raise low-density lipoprotein (LDL, or "bad") cholesterol but also lower the "good” high-density lipoprotein (HDL) cholesterol. In fact, trans fats are so harmful to your health that the Institute of Medicine says there is no safe level of intake and recommends consuming as little of this fat as possible. • The American Heart Association put a number on "as little as possible," advising Americans to keep their trans fat intake below 1% of total calories. To make it easier for you to reduce trans fat intake, the U.S. Food and Drug Administration now requires food manufacturers to list the amount of this fat on the Nutrition Facts panel. (The amount is listed beneath the entry for saturated fat.)

33. A John Hopkins Study 2009 • The government allows manufacturers to say their product has no trans fats if it has less than half a gram (0.5 g) per serving. That mean "if you’re eating more than one serving of a "no trans fat" product or several products that are labeled "not a significant source of trans fat," you could be eating more trans fat than you realize. • If the list of ingredients mentions partially hydrogenated oil, hydrogenated oil, or shortening, the product isn’t technically trans fat free. When eating these products, you should estimate that you are getting 1 g of trans fat for every two servings you eat. You can find the size of a serving at the top of the Nutrition Facts panel. Beware: It might be smaller than the amount you usually consume. • Also, be on the lookout for palm oil, palm kernel oil, and coconut oil in the ingredient list. These are the saturated fats commonly used in place of trans fat, because they are similar in taste and stability. When eating these products, check the Nutrition Facts panel for the grams of saturated fat per serving. You want to limit your daily intake of saturated fat to less than 7% of total calories.

34. Breast cancer study heaps more misery on trans-fats (By Stephen Daniells, 15-Apr-2008) • An increased intake of trans-fatty acids may raise the risk of breast cancer by 75 per cent, suggest the results from the French part of the European Prospective Investigation into Cancer and Nutrition. • Almost 20,000 women provided data for the study, which looks set to increase the pressure on the food industry to remove trans fatty acids from their products and reformulate. • Writing in the American Journal of Epidemiology, Veronique Chajes from the Centre National de la Recherche Scientifique (CNRS) reports that high blood levels of trans fatty acids, but not cis fatty acids, was associated with a significant increase in breast cancer risk. • "A high serum level of trans-monounsaturated fatty acids, presumably reflecting a high intake of industrially processed foods, is probably one factor contributing to increased risk of invasive breast cancer in women," wrote the researchers. • "At this stage, we can only recommend limiting the consumption of processed foods, the source of industrially produced trans-fatty acid," they added.

35. (single to single) p.575

36. 14 to 22 carbons 12 to 32 carbons No double bonds Waxes fruits, beeswax, earwax? Esters of fatty acids and long chain alcoholsWater insoluble and not easily hydrolyzed.Often found in protective coatings. Solids at room temp Vitamin A palmitate from palmitic acid and retinol NOT a wax A liquid

37. Complex saponifiable fats/oils

38. Complex lipids Phospholipids contain an alcohol, two fatty acids, and a phosphate ester. In glycerophospholipids, the alcohol is glycerol. In sphingolipids, the alcohol is sphingosine. Glycolipids Complex lipids that contain a carbohydrate.

39. Messengers esters Lipid A biological compound that is soluble only in nonpolar solvents. cholesterol Singleester triester Also an energy storage (9 Cal/g)

40. Complex Lipids Figure 21.1 Schematic diagram of simple and complex lipids. Variable long chain Fixed long chain + - - - + E = ester connection A = amide connection

41. Membranes Complex lipids form the membranes around cells and small structures within cells. In aqueous solution, complex lipids spontaneously form into a lipid bilayer, with a back-to-back arrangement of lipid monolayers. Polar (hydrophilic) head groups are in contact with the aqueous environment. Nonpolar (hydrophobic) tails are buried within the bilayer and shielded from the aqueous environment. The major force driving the formation of lipid bilayers is hydrophobic interaction. The arrangement of hydrocarbon tails in the interior can be rigid (if rich in saturated fatty acids) or fluid (if rich in unsaturated fatty acids).

42. Fluid Mosaic Model

43. ester ester Phosphoglycerides A phospholipid that contains an alcohol (usually an amino alcohol) ester diester ester

44. Glycerophospholipids A phosphatidic acid The fatty acid on carbon 2 of glycerol is always unsaturated. Further esterification with a low-molecular-weight alcohol (next screen) gives a glycerophospholipid.

45. Glycerophospholipids Glycerophospholipids are the second most abundant group of naturally occurring lipids. They are also called phosphoglycerides. Found almost exclusively in plant and animal membranes, which typically consist of 40% -50% phosphoacylglycerols and 50% - 60% proteins. The most abundant glycerophospholipids are derived from phosphatidic acid, a molecule in which glycerol is esterified with two molecules of fatty acid and one of phosphoric acid. The three most abundant fatty acids in phosphatidic acids are palmitic (16:0), stearic (18:0), and oleic (18:1).

46. Phospholipids: Phosphoglycerides

47. Important Phosphoglycerides Lecithins most abundant- Contain the amino alcohol choline. Important cell membrane component. Emulsifying agent. Cephalins Contain ethanolamine or serine as the alcohol. Found in most cell membranes, especially brain tissue.

48. Examples 1 Lecithin 2 In Lecithins the 1 and 2 position fatty acids can vary to give a multitude of lecithins – +

49. Example cephalins 1 2 – + – serine In all cells in small amounts but are abundant in brain cells

50. Sphingolipids • Found in the coatings of nerve axons (myelin). • Contain the long-chain aminoalcohol, sphingosine, from which this class of compounds in named.