1. 1 Lipids Lipids are the hydrophobic compounds of C, H and O With much higher ratio of hydrogen to oxygen than carbohydrates Most are insoluble in water but soluble in non polar compounds

2. 2 Lipids Types of Lipids Fatty Acids Fats, and Oils Chemical Properties of Triglycerides

3. 3 Properties of fats and oils fats are solids or semi solids oils are liquids melting points and boiling points are not usually sharp (most fats/oils are mixtures) when shaken with water, oils tend to emulsify pure fats and oils are colorless and odorless (color and odor is always a result of contaminants) – i.e. butter (bacteria give flavor, carotene gives color)

4. 4 Examples of oils Olive oil – from Oleo europa (olive tree) Corn oil – from Zea mays Peanut oil – from Arachis hypogaea Cottonseed oil – from Gossypium Sesame oil – from Sesamum indicum Linseed oil – from Linum usitatissimum Sunflower seed oil – from Helianthus annuus Rapeseed oil – from Brassica rapa Coconut oil – from Cocos nucifera

5. 5 Non-drying, semi-drying and drying oils based on the ease of autoxidation and polymerization of oils (important in paints and varnishes) the more unsaturation in the oil, the more likely the “drying” process –Non-drying oils: Castor, olive, peanut, rapeseed oils –Semi-drying oils Corn, sesame, cottonseed oils –Drying oils Soybean, sunflower, hemp, linseed, tung, oiticica oils

6. 6 Types of Lipids Lipids with fatty acids Waxes Fats and oils (trigycerides) Phospholipids Sphingolipids Lipids without fatty acids Steroids

7. 7 Fatty Acids Long-chain carboxylic acids Insoluble in water Typically 12-18 carbon atoms (even number) Some contain double bonds corn oil contains 86% unsaturated fatty acids and 14% saturated fatty acids

8. 8 Saturated and Unsaturated Fatty Acids Saturated = C–C bonds Unsaturated = one or more C=C bonds

9. 9 Structures Saturated fatty acids Fit closely in regular pattern Unsaturated fatty acids Cis double bonds

10. 10 Properties of Saturated Fatty Acids Contain only single C–C bonds Closely packed Strong attractions between chains High melting points Solids at room temperature

11. 11 Properties of Unsaturated Fatty Acids Contain one or more double C=C bonds Nonlinear chains do not allow molecules to pack closely Few interactions between chains Low melting points Liquids at room temperature

12. 12 Fatty acids Common fatty acids n = 4 butyric acid (butanoic acid) n = 6 caproic acid (hexanoic acid) n = 8 caprylic acid (octanoic acid) n = 10 capric acid (decanoic acid)

13. 13 Fatty acids common FA’s: n = 12: lauric acid (n-dodecanoic acid; C 12:0 ) n = 14: myristic acid (n-tetradecanoic acid; C 14:0 ) n = 16: palmitic acid (n-hexadecanoic acid; C 16:0 ) n = 18; stearic acid (n-octadecanoic acid; C 18:0 ) n = 20; arachidic (eicosanoic acid; C 20:0 ) n= 22; behenic acid n = 24; lignoceric acid n = 26; cerotic acid

14. 14 Typical fish oil supplements

15. 15 Learning Check L1 How would the melting point of stearic acid compare to the melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain. stearic acid (18 C) saturated oleic acid (18 C) one double bond linoleic acid (18 C) two double bonds

16. 16 Solution L1 Stearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Because linoleic has two double bonds, it would have a lower mp than oleic acid, which has one double bond. stearic acid mp 69°C oleic acid mp 13°C linoleic acid mp -17°C

17. 17 Fats and Oils Formed from glycerol and fatty acids

18. 18 Triglycerides (triacylglcerols) Esters of glycerol and fatty acids

19. 19 Learning Check L2 What are the fatty acids in the following triglyceride?

20. 20 Solutions L2 What are the fatty acids in the following triglyceride? Stearic acid Oleic acid Myristic acid

21. 21 Properties of Triglycerides Hydrogenation Unsaturated compounds react with H 2 Ni or Pt catalyst C=C bonds C–Cbonds Hydrolysis Split by water and acid or enzyme catalyst Produce glycerol and 3 fatty acids

22. 22 Hydrogenation

23. 23 Hydrogenated fats hydrogenation leads to either saturated fats and or trans fatty acids the purpose of hydrogenation is to make the oil/fat more stable to oxygen and temperature variation (increase shelf life) example of hydrogenated fats: Crisco, margarine

24. 24 Product of Hydrogenation Hydrogenation converts double bonds in oils to single bonds. The solid products are used to make margarine and other hydrogenated items.

25. 25 Hydrolysis Triglycerides split into glycerol and three fatty acids (H + or enzyme catalyst)

26. 26 Saponification and Soap Hydrolysis with a strong base Triglycerides split into glycerol and the salts of fatty acids The salts of fatty acids are “soaps” KOH gives softer soaps

27. 27 Saponification

28. 28 Soaps Process of formation is known as saponification –Types of soaps: Sodium soap – ordinary hard soap Potassium soap – soft soap (shaving soaps are potassium soaps of coconut and palm oils) Castile soap – sodium soap of olive oil Green soap – mixture of sodium and potassium linseed oil Transparent soap – contains sucrose Floating soap – contains air Calcium and magnesium soaps are very poorly water soluble (hard water contains calcium and magnesium salts –these insolubilize soaps)

29. 29 Learning Check L3 What are the products obtained from the complete hydrogenation of glyceryl trioleate? (1) Glycerol and 3 oleic acids (2) Glyceryltristearate (3) Glycerol and 3 stearic acids

30. 30 Solution L3 What are the products obtained from the complete hydrogenation of glyceryl trioleate? 2. Glyceryltristearate

31. 31 Lipids Phospholipids Steroids and Cholesterol Plasma (Cell)Membranes

32. 32 Phosphoglycerides Most abundant lipids in cell membranes Control cell permeability FATTY ACID glycerol PO 4 Amino alcohol

33. 33 Steroids Steroid nucleus 3 cyclohexane rings 1 cyclopentane ring steroid nucleus

34. 34 Cholesterol Most abundant steroid in the body Add methyl CH 3 - groups, alkyl chain, and - OH to steroid nucleus

35. 35 Cholesterol in the Body Cellular membranes Myelin sheath, brain, and nerve tissue Bile salts Hormones Vitamin D

36. 36 Bile Salts Synthesized in the liver from cholesterol Stored in the gallbladder Secreted into small intestine Mix with fats to break them part Emsulsify fat particles

37. 37 Steroid Hormones Chemical messengers in cells Sex hormones Androgens in males (testosterone) Estrogens in females (estradiol) Adrenocorticosteroids from adrenal glands mineralocorticoids (electrolyte balance) glucocorticoids regulate glucose level

38. 38 Sex Hormones

39. 39 Plasma Membranes Surround cells Lipid bilayer pf phospholipids Nonpolar hydrocarbon tails in center Polar (hydrophilic) sections on outside Some unsaturated fatty acids give flexibility Keep aqueous contents inside Allow certain biochemicals to pass through

40. 40 Diagram of a Plasma Membrane Polar sections Nonpolar tails