Lipids. Classes of Lipids. Types of Lipids. Saturated and Unsaturated Fatty Acids. Fatty Acids Lipids 15.2 Fatty Acids

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1 hapter Fatty Acids 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. 1 2 Types of lasses of The types of lipids containing fatty acids are waxes fats and oils (triacylglycerols) glycerophospholipids prostaglandins The types of lipids that do not contain fatty acids are steroids 3 4 Fatty Acids Saturated and Unsaturated Fatty Acids Fatty acids are long-chain carboxylic acids. typically carbon atoms. insoluble in water. saturated or unsaturated. live oil contains 84% unsaturated fatty acids and 16% saturated fatty acids. Fatty acids are saturated with all single bonds. unsaturated with one or more double = bonds. H palmitic acid, a saturated acid H palmitoleic acid, an unsaturated acid 5 6

2 Properties of Saturated Fatty Acids Properties of Unsaturated Fatty Acids Saturated fatty acids contain only single bonds. are closely packed. have strong attractions between chains. have high melting points. are solids at room temperature. H H H Unsaturated fatty acids contain one or more cis double = bonds. 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. H H H H H H kinks in chain 7 8 Melting Points of Some Saturated Fatty Acids Melting Points of Some Unsaturated Fatty Acids 9 10 Learning heck Assign the melting points of 17, 13, and 69 to the correct fatty acid. Explain. stearic acid (18 ) saturated oleic acid (18 ) one double bond linoleic acid (18 ) two double bonds 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 saturated oleic acid mp 13 linoleic acid mp -17 most unsaturated 11 12

3 hapter 15 Waxes 15.3 Waxes, Fats, and ils Waxes are esters of saturated fatty acids and long-chain alcohols. coatings that prevent loss of water by leaves of plants Fats and ils: Triacylglycerols Triacylglycerols Fats and oils are also called triacylglycerols. esters of glycerol. produced by esterification. Formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids. In a triacylglycerol, glycerol forms ester bonds with three fatty acids. Ester Bonds Formation of a Triacylglycerol Learning heck Glycerol + three fatty acids triacylglycerol H 2 H H (H 2 ) 14 H H + H 2 H H (H 2 ) 14 H (H 2 ) 14 H 2 (H 2 ) 14 H (H 2 ) H 2 What are the fatty acids in the following triacylglycerol? H 2 (H 2 ) 16 H (H 2 ) 7 H H(H 2 ) 7 H 2 (H 2 ) 12 H 2 (H 2 )

4 Melting Points of Fats and ils H 2 H H 2 Stearic acid (H 2 ) 16 leic acid (H 2 ) 7 H H(H 2 ) 7 (H 2 ) 12 Myristic acid A fat is usually solid at room temperature. is prevalent in meats, whole milk, butter, and cheese. An oil is usually liquid at room temperature. is prevalent in plants such as olive and safflower ils with Unsaturated Fatty Acids ils have more unsaturated fats. have cis double bonds that cause kinks in the fatty acid chains. with kinks in the chains do not allow the triacylglycerol molecules to pack closely. have lower melting points than saturated fatty acids. are liquids at room temperature. Diagram of Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains with kinks cannot pack closely Percent Saturated and Unsaturated Fatty Acids In Fats and ils hapter hemical Properties of Triacylglycerols 23 24

5 hemical 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. Hydrogenation of ils The hydrogenation of oils adds hydrogen (H 2 ) to the carbon atoms of double bonds. converts double bonds to single bonds. increases the melting point. produces solids, such as margarine and shortening Hydrogenation Learning heck H Ni 2 (H 2 ) 5 H H(H 2 ) 7 + 3H 2 H (H 2 ) 5 H H(H 2 ) 7 H 2 (H 2 ) 14 H 3 H 2 (H 2 ) 5 H H(H 2 ) 7 H (H Glyceryl tripalmitoleate 2 ) 14 (tripalmitolean) H 2 (H 2 ) 14 Glyceryl tripalmitate (tripalmitin) What products are obtained from the complete hydrogenation of glyceryl trioleate? 1. Glycerol and 3 oleic acids 2. Glyceryltristearate 3. Glycerol and 3 stearic acids lestra TM, a Fat Substitute What products are obtained from the complete hydrogenation of glyceryl trioleate? 2. Glyceryltristearate lestra 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

6 is and Trans Fatty Acids Unsaturated fatty acids can be cis with bulky groups on same side of =. (H 2 ) 5 (H 2 ) 7 H cis = H H trans have bulky groups on opposite sides of =. (H 2 ) 5 H = trans H (H 2 ) 7 H Hydrogenation and Trans Fatty Acids Most naturally occurring fatty acids have cis double bonds. During hydrogenation, some cis double bonds are converted to trans double bonds. In the body, trans fatty acids behave like saturated fatty acids. It is estimated that 2-4% of our total alories is in the form of trans fatty acid. Several studies reported that trans fatty acids raise LDLcholesterol and lower HDL-cholesterol Hydrogenation of Unsaturated Fats Learning heck (1) True or (2) false: A. There are more unsaturated fats in vegetable oils. B. Vegetable oils have higher melting points than fats.. Hydrogenation of oils converts some cis-double bonds to trans-double bonds. D. Animal fats have more saturated fats Hydrolysis (1) True or (2) false: A. T There are more unsaturated fats in vegetable oils. B. F Vegetable oils have higher melting points than fats.. T Hydrogenation of oils converts some cis-double bonds to trans- double bonds. D. T Animal fats have more saturated fats. In hydrolysis, triacylglycerols split into glycerol and three fatty acids. an acid or enzyme catalyst is required. H 2 (H 2 ) 14 H H + (H 2 ) 14 + H 2 H 2 (H 2 ) 14 H 2 H H H + H (H 2 ) 14 H 2 H 35 36

7 Saponification and Soap Saponification Saponification 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). with KH gives softer soaps. H 2 H H 2 (H 2 ) 14 (H 2 ) 14 (H 2 ) NaH H 2 H H H + 3Na + - (H 2 ) 14 H 2 H soap Learning heck What products are obtained from the complete hydrolysis of glyceryl trioleate? 1. Glycerol and 3 oleic acids 2. Glyceryl tristearate 3. Glycerol and 3 stearic acids What products are obtained from the complete hydrolysis of glyceryl trioleate? 1. Glycerol and 3 oleic acids Learning heck Write the product of the following reaction: H 2 H H 2 (H 2 ) 5 H H(H 2 ) 7 (H 2 ) 5 H H(H 2 ) 7 + 3H 2 Ni (H 2 ) 5 H H(H 2 ) 7 H 2 H H 2 (H 2 ) 14 (H 2 ) 14 (H 2 )

8 hapter 15 Glycerophospholipids 15.5 Glycerophospholipids Glycerol Fatty acid Fatty acid P 4 Amino alcohol Glycerophospholipids are the most abundant lipids in cell membranes. composed of glycerol, two fatty acids, phosphate, and an amino alcohol. Glycerol Fatty acid Fatty acid P 4 Amino alcohol Polarity of Glycerophospholipids A glycerophospholipid has two nonpolar fatty acid chains. a phosphate group and a polar amino alcohol. Structure and Polarity of a Glycerophospholipid + + H H 2 H 2 N H H 2 H 2 NH 3 holine Ethanolamine + NH 3 H H 2 H Serine Amino alcohols Lecithin and ephalin Learning heck Lecithin and cephalin are glycerophospholipids abundant in brain and nerve tissues. found in egg yolk, wheat germ, and yeast. Identify each as A. fatty acid B. triacylglycerol. amino alcohol D. glycerophospholipid 1. glyceryl trioleate 2. cephalin 3. choline 4. palmitic acid 47 48

9 hapter 15 Identify each as A. fatty acid B. triacylglycerol. amino alcohol D. glycerophospholipid 1. glyceryl trioleate B. triacylglycerol 2. cephalin D. Glycerophospholipid 3. choline. amino alcohol 4. palmitic acid A. fatty acid 15.6 Steroids: holesterol and Steroid Hormones H Steroid Nucleus A steroid nucleus consists of 3 cyclohexane rings. 1 cyclopentane ring. no fatty acids. holesterol holesterol is the most abundant steroid in the body. has methyl - groups, alkyl chain, and -H attached to the steroid nucleus. steroid nucleus H holesterol in the Body holesterol in Foods holesterol 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. A normal, open artery. An artery clogged by cholesterol plaque holesterol is considered elevated if plasma cholesterol exceeds 200 mg/dl. is synthesized in the liver and obtained from foods

10 Learning heck Match the components of the cholesterol molecule with the following: carbon chain hydroxyl group steroid nucleus methyl group Match the components of the cholesterol molecule with the following: _D carbon chain _A_hydroxyl group _ steroid nucleus _B_methyl group D D B B A H A H Lipoproteins Types of Lipoproteins Lipoproteins combine lipids with proteins and phospholipids. Lipoproteins differ in density, composition, and function. include low-density lipoproteins (LDLs) and highdensity lipoproteins (HDLs). are soluble in water because the surface consists of polar lipids Transport of Lipoproteins in the Body Steroid Hormones Steroid hormones are chemical messengers in cells. sex hormones. - androgens in males (testosterone) - estrogens in females (estradiol) Adrenocortical hormones from adrenal glands. - mineralocorticoids (electrolyte balance) - glucocorticoids (regulate glucose level) 59 60

11 Steroid Hormones Adrenal orticosteroids Steroid hormones are produced from cholesterol. include sex hormones such as androgens (testosterone) in males and estrogens (estradiol) in females. Steroid hormones called adrenal corticosteroids are produced by the adrenal glands located on the top of each kidney. include aldosterone, which regulates electrolytes and water balance by the kidneys. include cortisone, a glucocorticoid, which increases blood glucose level and stimulates the synthesis of glycogen in the liver Anabolic Steroids Adrenal orticosteroids 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 Learning heck Identify each lipid as a (1) fatty acid, (2) steroid, or (3) triacylglycerol. A. cholesterol B. stearic acid. glyceryl tristearate D. estradiol E. contains no fatty acids Identify each lipid as a (1) fatty acid, (2) steroid, or (3) triacylglycerol. A. 2 cholesterol B. 1 stearic acid. 3 glyceryl tristearate D. 2 estradiol E. 2 contains no fatty acids 65 66

12 hapter 15 ell Membranes 15.7 ell Membranes ell 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 Fluid Mosaic Model of ell Membranes Fluid Mosaic Model of ell 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 Transport Through ell Membranes Transport Pathways Through ell Membranes The transport of substances through cell membranes involves diffusion (passive transport), which moves particles from a higher to a lower concentration. facilitated transport, which uses protein channels to increase the rate of diffusion. active transport, which moves ions against a concentration gradient

13 Learning heck The transport of particles across a cell membrane from high concentration to low concentration is called 1. facilitated transport. 2. diffusion. 3. active transport. The transport of particles across a cell membrane from high concentration to low concentration is called 2. diffusion