Chapter 15: Fats and Oils The Triglycerides We Eat © 2003 John Wiley and Sons Publishers Courtesy PhotoDisc Inc./Getty Images

Figure 15.1: The effect of polyunsaturation. © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

Fats (solid triglycerides) and an oil (a liquid triglyceride). © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

18.1Lipids 18.2Fatty Acids Chapter 18 Lipids

Lipids Lipids are: Biomolecules that contain fatty acids or a steroid nucleus. Soluble in organic solvents, but not in water. Named for the Greek word lipos, which means “fat.” Extracted from cells using organic solvents.

Classes of Lipids

Fatty acids are: Long-chain carboxylic acids that have an even number (usually 12-18) of carbon atoms. Insoluble in water. Saturated or unsaturated. Fatty Acids

Fatty Acid Formulas The formulas for fatty acids are written as condensed and line-bond formulas. For example caprylic acid with 8 carbon atoms can be written as: CH 3 —(CH 2 ) 6 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —COOH O || CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —C—OH

Saturated Fatty Acids Saturated fatty acids have single C–C bonds.

Review

Saturated fatty acids have: Molecules that fit closely together in a regular pattern. Strong attractions between fatty acid chains. High melting points that makes them solids at room temperature. Saturated Fatty Acids

Unsaturated Fatty Acids Unsaturated fatty acids typically contain cis double bonds.

Unsaturated Fatty Acids Unsaturated fatty acids have cis C=C bonds.

Figure 15.6: Planarity and the carbon—carbon double bond. The two carbons and atoms W, X, Y, and Z, all lie in the same plane. © 2003 John Wiley and Sons Publishers

Figure 15.7: Geometric isomers. © 2003 John Wiley and Sons Publishers

Figure 15.8: cis-2-Butene (left) and trans-2-butene (right). © 2003 John Wiley and Sons Publishers Courtesy Michael Pique, The Scripps Research Institute, CA

Figure 15.9: Molecular packing in glyceryl tristearate and glyceryl trioleate. © 2003 John Wiley and Sons Publishers

Unsaturated fatty acids: Have nonlinear chains that do not allow molecules to pack closely. Have low melting points. Are liquids at room temperature. Unsaturated Fatty Acids

Assign the melting points –17°C, 13°C, and 69°C to the following 18 C fatty acids. Explain. Stearic acid saturated Oleic acid one double bond Linoleic acid two double bonds Learning Check

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

Olive Oil Olive oil contains a high percentage of oleic acid. Oleic acid is a monounsaturated fatty acid with one cis double bond.

Figure 15.2: The general structure of a triglyceride. R, R’ and R” represent the long, fatty acid side chains. © 2003 John Wiley and Sons Publishers

Figure 15.3: Fatty acid content of fats and oils (typical percentages). © 2003 John Wiley and Sons Publishers

Omega-6 and Omega-3 Fatty Acids The first double bond: In vegetable oils is at carbon 6 (omega-6). In fish oils is at carbon 3 (omega-3).

Learning Check Write a fatty acid with 10 carbon atoms that is: A. Saturated B. Monounsaturated omega-3 C. Monounsaturated omega-6

Solution Write a fatty acid with 10 carbon atoms that is: A. Saturated CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —COOH B. Monounsaturated omega-3 CH 3 —CH 2 —CH=CH—CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —COOH C. Monounsaturated omega-6 CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —CH 2 —COOH

Partial hydrogenation of vegetable oils produces a mixture of triglycerides that soften and melt near body temperature. © 2003 John Wiley and Sons Publishers Courtesy Marti Pie/The Image Bank

Steroids are: Lipids containing the steroid nucleus, which is a fused structure of four rings. Found in cholesterol, bile salts, hormones, and vitamin D. Steroids Steroid nucleus

Estrogen: Female sex hormone Fertilized egg can grow breast make milk Cortisol : maintain blood pressure, immune function anti- inflammatory burst of energy regulator of the salt and water balance

Cholesterol is: The most abundant steroid in the body. Composed of the steroid nucleus with methyl CH 3 – groups, an alkyl chain, and a hydroxyl group –OH attached. Cholesterol

Cholesterol in Foods Cholesterol: Is considered elevated if plasma cholesterol exceeds mg/dL. Is synthesized in the liver and obtained from foods.

Types of LipoproteinsLipoproteins : Differ in density, composition, and function. Include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs).

Transport of Lipoproteins in the Body Chilomicrons

Bile Salts Bile salts: Are synthesized from cholesterol and stored in the gall bladder. Emulsify fats and oils to give a greater surface area for lipid digesting enzymes.

Steroid Hormones Steroid hormones: Are produced from cholesterol. Include sex hormones such as androgens (testosterone) in males and estrogens (estradiol) in females.

Anabolic Steroids Anabolic steroids: Are derivatives of testosterone. Are used illegally to increase muscle mass. Have side effects including fluid retention, hair growth, sleep disturbance, and liver damage.

Cholesterol: a sterol that contributes to cardiovascular disease. © 2003 John Wiley and Sons Publishers Courtesy Andy Washnik

Figure 15.4: Cholesterol. © 2003 John Wiley and Sons Publishers

Figure 15.5: The core molecular structure of a steroid. © 2003 John Wiley and Sons Publishers

Plant products, including vegetables and vegetable oils, are all free of cholesterol. © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

The body stores energy as the triglycerides of fat or adipose tissue. © 2003 John Wiley and Sons Publishers Courtesy Jerry Ohlinger’s

© 2003 John Wiley and Sons Publishers Does catalytic hydrogenation tend to convert fats to oils or oils to fats? QUESTION

© 2003 John Wiley and Sons Publishers Of the fats and oils of Table 15.2, which contains the most highly saturated side chains? Which contains the most highly unsaturated side chains? QUESTION

© 2003 John Wiley and Sons Publishers Which of the following triglycerides would you expect to be least useful in the manufacture of a chocolate candy bar: (a) glyceryl trilinoleate; (b) glyceryl tripalmitate; (c) glyceryl trioleate? Explain. (You may find it useful to refer to Table 15.1) QUESTION

© 2003 John Wiley and Sons Publishers Give two reasons why switching from a diet rich in red meat and animal products to one with plenty of fruits, vegetables, and other plant products might help lower serum cholesterol. QUESTION

© 2003 John Wiley and Sons Publishers You are a manufacturer of varnishes that have drying oils as major ingredients. One of your laboratory chemists suggests that you add an antioxidant to the varnishes to improve their shelf life. How would you respond to this suggestion? Explain. QUESTION

© 2003 John Wiley and Sons Publishers Why does the hydrogenation of a polyunsaturated triglyceride raise its melting point? QUESTION

© 2003 John Wiley and Sons Publishers Considering the Perspective as the terminal section of this chapter, what omega designation would you give to this current section? QUESTION

© 2003 John Wiley and Sons Publishers Suppose you’re 15 pounds overweight. That is, you are carrying around, at all times, an excess of 15 pounds of adipose tissue. Translate this into the equivalent number of excess stored Calories you are carrying with you at all times. QUESTION