Lipids 1

Lipids are Biomolecules that are nonpolar – Soluble in organic solvents but not in water. Named for the Greek word lipos, (means “fat”) 2 Types of lipids we’ll look at: Fatty acids. Waxes. Fats and oils (triglycerides = triacylglycerols). Glycerophospholipids. Steroids.

Structures of Lipids 3

Fatty Acids Fatty acids Are long-chain carboxylic acids. Typically contain carbon atoms. Are insoluble in water. Can be saturated or unsaturated. 4

Fatty Acid Formulas The formulas for fatty acids are written as Condensed formulas. Line-bond formulas. For example caprylic acid with 8 carbon atoms. CH 3 —(CH 2 ) 6 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —COOH 5

Palmitic Acid Fatty Acid Formulas

Saturated Fatty Acids Saturated fatty acids have Single C–C bonds. Molecules that fit closely together in a regular pattern. Strong attractions between fatty acid chains. High melting points that make them solids at room temperature. 7

Some Saturated Fatty Acids 8

Fats and Other Lipids Saturated fatty acids have no carbon-to-carbon double bonds. Monounsaturated fatty acids have one carbon-to- carbon double bond. Polyunsaturated fatty acids have two or more carbon-to-carbon double bonds.

Unsaturated Fatty Acids Unsaturated fatty acids Have one or more double C=C bond Typically contain cis double bonds. 10

Unsaturated Fatty Acids Unsaturated fatty acids Have “kinks” in the fatty acid chains. Do not pack closely. Have few attractions between chains. Have low melting points. Are liquids at room temperature. 11 “kinks” in chain

Unsaturated Fatty Acids 12

Melting Points of Some Fatty Acids 13

Learning Check Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain. stearic acid (18 C’s) saturated oleic acid (18 C’s) one double bond linoleic acid (18 C’s) two double bonds 14

Solution 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 saturated oleic acid mp 13°C linoleic acid mp -17°C most unsaturated 15

Omega-6 and Omega 3- Fatty Acids 16 Fatty acids  In vegetable oils are mostly omega-6 with the first C=C at C6 from the end. linoleic acid CH 3 ─(CH 2 ) 4 ─CH=CH─CH 2 ─CH=CH─(CH 2 ) 7 ─COOH 6  In fish oils are mostly omega-3 with the first C=C at C3 from the end. linolenic acid CH 3 ─CH 2 ─(CH=CH─CH 2 ) 3 ─(CH 2 ) 6 ─COOH 3

Some Omega-6 and Omega-3 Fatty Acids 17

Learning Check Match the following fatty acids with a term that best describes them: A.PolyunsaturatedD. Saturated B. monounsaturated omega-6E. monounsaturated C. monounsaturated omega-3 18 CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —CH 2 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —CH=CH—CH 2 —CH=CH—CH 2 —COOH

Solution Match the following fatty acids with a term that best describes them: A.PolyunsaturatedD. Saturated B. monounsaturated omega-6E. monounsaturated C. monounsaturated omega-3 19 CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —CH 2 —COOH CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH=CH—CH 2 —CH=CH—CH 2 —CH=CH—CH 2 —COOH A B E D

Waxes, Fats, and Oils 20

Waxes Waxes are Esters of saturated fatty acids and long-chain alcohols. Coatings that prevent loss of water by leaves of plants. 21

Fats and Oils: Triacylglycerols Fats and oils are Also called triglycerides or triacylglycerols. Esters of glycerol. Produced by esterification. Formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids. 22

Triglycerides In a triglyceride (triacylglycerol), Glycerol forms ester bonds with three fatty acids. 23

Fats and Other Lipids Triglycerides are triesters of glycerol and fatty acids.

Formation of a Triacylglycerol glycerol + 3 fatty acids triacylglycerol H 2 O +

Learning Check What are the fatty acids in the following triacylglycerol? 26 A.Palmitic Acid, Oleic Acid, Lauric Acid B.Stearic Acid, Oleic Acid, Lauric Acid C.Stearic Acid, Oleic Acid, Myristic Acid D.Palmitic Acid, Oleic Acid, Lauric Acid E.None of these

Solution 27 Stearic acid Oleic acid Myristic acid A.Palmitic Acid, Oleic Acid, Lauric Acid B.Stearic Acid, Oleic Acid, Lauric Acid C.Stearic Acid, Oleic Acid, Myristic Acid D.Palmitic Acid, Oleic Acid, Lauric Acid E.None of these

Melting Points of Fats and Oils A triacylglycerol that is a fat Is solid at room temperature. Solid fats have a high proportion of saturated fatty acids. Is prevalent in meats, whole milk, butter, and cheese. A triacylglycerol that is an oil Is liquid at room temperature. Liquid oils have a high proportion of unsaturated fatty acids. Is prevalent in plants such as olive and safflower. 28

Oils with Unsaturated Fatty Acids Oils Have more unsaturated fats. Have cis double bonds that cause “kinks” in the fatty acid chains. Cannot pack triacylglycerol molecules as close together as in fats. Have lower melting points than saturated fats. Are liquids at room temperature. 29

Olive Oil Contains a high percentage of oleic acid, which is a monounsaturated fatty acid with one cis double bond. 30 Unsaturated fatty acid chains have kinks that do not allow close packing.

31 Saturated & Unsaturated FAs In Fats and Oils

Fats and Other Lipids Iodine number is a measure of the degree of unsaturation of a fat or oil. Iodine number is the number of grams of I 2 that are consumed by 100 g of a fat or oil.

Fats and Other Lipids Iodine Number

Learning Check Which of the following fats or Oils would have the highest Iodine number (consume the most I 2 or Br 2 )? 34 A. Olive Oil B. Butter C. Coconut Oil D. Canola Oil E. Corn Oil

Solution Which of the following fats or Oils would have the highest Iodine number (consume the most I 2 or Br 2 )? 35 A. Olive Oil B. Butter C. Coconut Oil D. Canola Oil E. Corn Oil

Chemical Properties of Triacylglycerols The chemical reactions of triacylglycerols are similar to those of alkenes and esters. In hydrogenation, double bonds in unsaturated fatty acids react with H 2 in the presence of a Ni or Pt catalyst. In hydrolysis, ester bonds are split by water in the presence of an acid, a base, or an enzyme. 36

Hydrogenation of Oils Adds hydrogen (H 2 ) to the C’s of double bonds. Converts C=C’s to C-C’s. Increases the melting point. Produces solids (ie margarine and shortening). 37

Ni + 3H 2 glyceryl tripalmitoleate (tripalmitolean ) glyceryl tripalmitate (tripalmitin ) Hydrogenation 38

Learning Check What product(s) is obtained from the complete hydrogenation of glyceryl trioleate? Glycerol and 3 oleic acids 2. Glyceryltristearate 3. Glycerol and 3 stearic acids

1. Glycerol and 3 oleic acids 2. Glyceryltristearate 3. Glycerol and 3 stearic acids Solution What product(s) is obtained from the complete hydrogenation of glyceryl trioleate? 40

Olestra, A Fat Substitute Olestra is Used in foods as an artificial fat. Sucrose linked by ester bonds to several long- chain fatty chains. Not broken down in the intestinal tract. 41

Trans Fatty Acids and Hydrogenation Trans fatty acids Formed during hydrogenation when cis double bonds  trans. In the body behave like saturated fatty acids. Estimated to make up 2-4% of our total Calories. Reported to raise LDL-cholesterol and lower HDL-cholesterol. 42

Learning Check 43 (1) True or (2) False A. There are more unsaturated fats in vegetable oils. B. Vegetable oils have higher melting points than fats. C. Hydrogenation of oils converts some cis- double bonds to trans- double bonds. D. Animal fats have more saturated fats.

Solution (1) True or (2) False A. There are more unsaturated fats in vegetable oils. B. Vegetable oils have higher melting points than fats. C. Hydrogenation of oils converts some cis- double bonds to trans- double bonds. D. Animal fats have more saturated fats. 44 T T T F

Hydrolysis In hydrolysis, Triacylglycerols split into glycerol and 3 fatty acids. An acid or enzyme catalyst is required

Hydrolysis In hydrolysis, Triacylglycerols split into glycerol and 3 fatty acids. An acid or enzyme catalyst is required. 46

Saponification and Soap Saponification = Basic Hydrolysis Is the reaction of a fat with a strong base. Splits triacylglycerols into glycerol and the salts of fatty acids. Is the process of forming “soaps” (salts of fatty acids). 47 Sodium Oleate A “soap”

Saponification NaOH 3+ “soap”

Learning Check 49 What products are obtained from the complete hydrolysis of glyceryl tripalmitoleate? 1. Glycerol and 3 palmitoleic acids 2. Glyceryl tripamitate 3. Glycerol and 3 palmitic acids

Solution 50 What products are obtained from the complete hydrolysis of glyceryl tripalmitoleate? 1. Glycerol and 3 palmitoleic acids 2. Glyceryl tripamitate 3. Glycerol and 3 palmitic acids

Learning Check Write the product of the following reaction

Solution Write the product of the following reaction

Glycerophospholipids Glycerophospholipids are The most abundant lipids in cell membranes. Composed of glycerol, two fatty acids, phosphate and an amino alcohol. 53 Glycerol PO 4 Amino alcohol Fatty acid

Glycerophospholipids Are Polar A glycerophospholipid has Two nonpolar fatty acid chains. A phosphate group and a polar amino alcohol. CH 3 │ + + HO−CH 2 −CH 2 −N−CH 3 HO−CH 2 −CH 2 −NH 3 │ choline CH 3 ethanolamine + NH 3 │ Amino alcohols HO−CH 2 −CH−COO − serine 54

Structure and Polarity of A Glycerophospholipid 55

Lecithin and Cephalin Lecithin and cephalin are glycerophospholipids Abundant in brain and nerve tissues. Found in egg yolk, wheat germ, and yeast. 56

Learning Check Identify each as a A. fatty acid B. triacylglycerol C. amino alcoholD. glycerophospholipid 1. glyceryl trioleate 2. cephalin 3. choline 4. palmitic acid 57

Solution Identify each as a A. fatty acid B. triacylglycerol C. amino alcoholD. glycerophospholipid 1. glyceryl trioleate 2. cephalin 3. choline 4. palmitic acid 58 B. triacylglycerol D. glycerophospholipid C. amino alcohol A. fatty acid

Learning Check Identify the components and type of glycerophospholipid O ║ CH 2 − O −C −(CH 2 ) 16 −CH 3 O ║ CH − O −C −(CH 2 ) 16 −CH 3 + O NH 3 ║ │ CH 2 − O −P −O − CH 2 −CH−COO - │ O - 59

Solution Identify the components and type of glycerophospholipid O ║ CH 2 − O −C −(CH 2 ) 16 −CH 3 O2 stearic acids ║ CH − O −C −(CH 2 ) 16 −CH 3 + O NH 3 ║ │type = cephalin CH 2 − O −P −O − CH 2 −CH−COO - │ serine O - phosphate amino alcohol 60

Steroid Nucleus A steroid nucleus consists of 3 cyclohexane rings. 1 cyclopentane ring. No fatty acids. 61 steroid nucleus

Cholesterol Is the most abundant steroid in the body. Has methyl CH 3 - groups, alkyl chain, and -OH attached to the steroid nucleus. 62

Cholesterol in the Body Cholesterol in the body Is obtained from meats, milk, and eggs. Is synthesized in the liver. Is needed for cell membranes, brain and nerve tissue, steroid hormones, and Vitamin D. Clogs arteries when high levels form plaque. 63 A normal, open artery. An artery clogged by cholesterol plaque

Cholesterol in Foods Cholesterol is Synthesized in the liver. Obtained from foods. Considered elevated if plasma cholesterol exceeds 200 mg/dL. 64

Learning Check A C B D Match the components of the cholesterol molecule with the following: 1. ___ carbon chain3. ___hydroxyl group 2. ___ steroid nucleus4. ___methyl group

Solution Match the components of the cholesterol molecule with the following: 1. ___ carbon chain3. ___hydroxyl group 2. ___ steroid nucleus4. ___methyl group A C B D A BC D

Bile Salts Bile salts Synthesized in the liver from cholesterol. Stored in the gallbladder and secreted into the small intestine. Have a polar and a nonpolar region Mix with fats to break them part (Emulsify fat particles) 67

Lipoproteins Combine lipids with proteins and phospholipids. Are soluble in water because the surface consists of polar lipids. 68

Types of Lipoproteins Lipoproteins Differ in density, composition, and function. Include low-density lipoprotein (LDLs) and high- density lipoprotein (HDLs). 69

Transport of Lipoproteins in the Body 70

Steroid Hormones Steroid hormones Are chemical messengers in cells. Are produced from cholesterol. Include sex hormones such as androgens (testosterone) in males and estrogens (estradiol) in females. 71

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. 72

Learning Check Identify each as a 1. fatty acid 2. steroid 3. triacylglycerol 4. phospholipid 73 A. ____ cholesterol B. ____ glycerol, 2 fatty acids, phosphate, & choline C. ____ glyceryl tristearate D. ____estradiol E. _____bile salts F. ____ lipids in plasma membranes

Solution Identify each as a A. fatty acid B. steroid C. triacylglycerol D. phospholipid ____ cholesterol 2. ____glycerol, 2 fatty acids, phosphate, & choline 3. ____glyceryl tristearate 4. ____estradiol 5. ____bile salts 6. ____ reacts with lye to make soap C B D B B A or C

Cell Membranes Cell membranes Separate cellular contents from the external environment. Consist of a lipid bilayer made of two rows of phospholipids. Have an inner portion made of the nonpolar tails of phospholipids with the polar heads at the outer and inner surfaces. 75

Fluid Mosaic Model of Cell Membranes The lipid bilayer Contains proteins, carbohydrates, and cholesterol. Has unsaturated fatty acids that make cell membranes fluid-like rather than rigid. Has proteins and carbohydrates on the surface that communicate with hormones and neurotransmitters. 76

Fluid Mosaic Model 77 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Eleventh Edition Nancy Gardner CHEMISTRY AN INTRODUCTION TO GENERAL, ORGANIC, AND BIOLOGICAL CHEMISTRY CRS “Clicker” Questions Chapter 15 Lipids © 2012 Pearson Education, Inc.

15.1 All of the following lipids can be hydrolyzed to form fatty acids except ________. A. waxes B. oils C. glycerophospholipids D. steroids Learning Check

15.2 Which of the following fatty acids is saturated? A. linolenic acid B. palmitoleic acid C. steric acid D. oleic acid Learning Check

15.3 What characterizes a triacylglycerol? A. the presence of three –OH groups B. long-chain fatty acids with double bonds C. three fatty acids connected to glycerol by ester bonds D. the presence of a benzene ring Learning Check

15.4 Hydrogenation of unsaturated fatty acids produces what undesired side product? A. cis-fatty acids B. trans-fatty acids C. saturated fatty acids D. unsaturated fatty acids Learning Check

15.5 What groups replace a fatty acid in a glycerophospholipid? A. phosphate and an alcohol B. phosphate and a ketone C. phosphate and an amino alcohol D. phosphate and an aldehyde Learning Check

15.6 What characterizes a steroid compound? A. amino groups B. three fused rings C. four fused rings D. long carbon chains linked by an ester Learning Check

15.7 Where are the hydrophobic ends of the glycerophospholipids found in the cell? A. facing each other inside the cell wall B. facing outward on the cell wall C. in the cytoplasm D. in the nucleus Learning Check

15.10 Which fatty acid is not an essential fatty acid? A. oleic acid B. linoleic acid C. linolenic acid D. arachidonic acid Learning Check

15.11 Of the following, which one is NOT an omega-3 fatty acid? A. linoleic acid B. linolenic acid C. eicosapentaenoic acid D. docosahexaenoic acid Learning Check

15.12 Which of the following is the correct structure for a 10-carbon fatty acid called capric acid? A. B. C. D. Learning Check

15.13 What is the major form of energy storage for animals that hibernate? A. triacylglycerols B. steroids C. alkenes D. carbohydrates Learning Check

15.14 Which lipid in plasma has the most “bad” cholesterol? A. triacylglycerol B. phospholipids C. cholesterol D. cholesteryl esters Learning Check

© 2013 Pearson Education, Inc. a.Polyglycerides b.Monoglycerides c.Diglycerides d.Triglycerides e.Tetraglycerides Learning Check

© 2013 Pearson Education, Inc. a.Polyglycerides b.Monoglycerides c.Diglycerides d.Triglycerides e.Tetraglycerides Solution

a.Trans fatty acids b.Unsaturated fatty acids c.Omega-3 fatty acids d.Both a and b e.Both b and c CH 3 (CH 2 CH=CH) 5 (CH 2 ) 3 COOH © 2013 Pearson Education, Inc. Learning Check

CH 3 (CH 2 CH=CH) 5 (CH 2 ) 3 COOH Eicosapentanoic acid (EPA) an Omega-3 fatty acid cis-oleic acid © 2013 Pearson Education, Inc. a.Trans fatty acids b.Unsaturated fatty acids c.Omega-3 fatty acids d.Both a and b e.Both b and c Solution