1 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Lipids Chapter 17 Lipids Lectures

2 © 2013 Pearson Education, Inc. Chapter 17, Section 1 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 nonpolar organic solvents.  natural components of cell membranes, fat-soluble vitamins, and steroid hormones.

3 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Lipids There are 2 types of lipids;  those that contain the structural component of a fatty acid; and  those that contain the structural component of a four member steroid molecule.

4 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Types of Lipids The lipids that contain fatty acids are  waxes,  fats and oils (triacylglycerols),  glycerophospholipids, and  prostaglandins. The types of lipids that do not contain fatty acid chains are steroids.

5 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Types of Fatty Acid Lipids

6 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Which lipids contain the alcohol glycerol? A. steroids and waxes B. triacylglycerols and glycerophospholipids C. sphingolipids and glycerophospholipids D. glycerophospholipids and waxes

7 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Which lipids contain the alcohol glycerol? A. steroids and waxes B. triacylglycerols and glycerophospholipids C. sphingolipids and glycerophospholipids D. glycerophospholipids and waxes Answer is B. Triacylglycerols and glycerophospholipids contain the alcohol glycerol.

8 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Fatty Acids Chapter 17 Lipids Lectures

9 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Fatty Acids Fatty acids  contain long-chain hydrocarbons with a carboxylic acid.  typically contain 12 to 18 carbon atoms.  are insoluble in water.  can be saturated or unsaturated.

10 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Fatty Acid Formulas The formulas for fatty acids are written as  condensed structural formulas.  skeletal formulas. Insert structures of lauric acid pg 600, both condensed structural formula and skeletal formulas

11 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Saturated fatty acids have  only single C—C bonds.  molecules that fit closely together in a regular pattern.  have properties similar to alkanes. Saturated Fatty Acids

12 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Saturated Fatty Acids

13 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Unsaturated Fatty Acids Unsaturated fatty acids  have one or more doublebond.  that are naturally occurring have one or more cis double bond insert picture of cis and trans fatty acid from top of pg 602

14 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Monounsaturated Fatty Acids Unsaturated fatty acids with one double bond are called monounsaturated fatty acids. Insert table 17.1 monounsaturated fatty acids.

15 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Polyunsaturated Fatty Acids Unsaturated fatty acids with more than one double bond are called polyunsaturated fatty acids. Insert table 17.1 polyunsaturated fatty acids.

16 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Properties of Saturated Fatty Acids Saturated fatty acids  fit closely together in a regular pattern.  have significant dispersion forces between chains.  have higher melting points.  are solids at room temperature.

17 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Properties of Unsaturated Fatty Acids Unsaturated fatty acids  have “kinks” in the fatty acid chains.  do not pack closely.  have fewer attractions between chains.  have lower melting points.  are liquids at room temperature. “kinks” in chain

18 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Assign the melting point (mp) of −17°C, 13°C, or 69°C to each one of the following 18-carbon fatty acids, and list the fatty acids in order from highest to lowest melting point. Explain. A. oleic acid B. stearic acid C. linoleic acid

19 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Stearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Oleic acid, which has one double bond, has a higher mp than linoleic acid, which has two double bonds. B. stearic acid mp 69°Csaturated A. oleic acid mp 13°C unsaturated with one double bond C. linoleic acid mp −17°C unsaturated with two double bonds

20 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Prostaglandins Prostaglandins have  20 carbon atoms in their fatty acid chains.  differ by the substituents attached to the 5-carbon ring.

21 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Prostaglandins and Physiological Effects Prostaglandins have potent physiological effects.  Some increase blood pressure.  Some lower blood pressure.  Some stimulate contractions and relaxation of smooth muscle in the uterus during the birth process and menstrual cycle. When tissues are injured, arachidonic acid in the blood is converted to PGE 1 and PGF 2 that produce inflammation and pain in the area.

22 © 2013 Pearson Education, Inc. Chapter 17, Section 1 NSAIDs and Prostaglandins Several nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, block production of prostaglandins decreasing pain, inflammation, and fever. Insert Picture of arachidonic acid conversion, top page 605.

23 © 2013 Pearson Education, Inc. Chapter 17, Section 1 NSAIDs and Prostaglandins Other NSAIDs include naproxen (Aleve and Naprosyn), ketoprofen (Actron), and nabumetone (Relafen). Long-term use of such products can result in liver, kidney, and gastrointestinal damage.

24 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Omega-3 and Omega-6 Fatty Acids Fish and vegetable oils have high levels of unsaturated fats.  In vegetable oils, they are mostly omega-6 with the first at C6. Linoleic acid  In fish oils, they are mostly omega-3 with the first at C3. CH 3 ─CH 2 ─(CH═CH─CH 2 ) 3 ─(CH 2 ) 6 ─COOH 1 3 Linolenic acid

25 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Omega-6 and Omega-3 Fatty Acids

26 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Omega-3 Fatty Acids Omega-3 fatty acids  lower the tendency of blood platelets to stick together, thereby reducing the possibility of blood clots.  can help reduce risk of heart disease.  are found in salmon, tuna, and herring.

27 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Draw the condensed structural formulas for each of the fatty acids with 10 carbon atoms that follow. A. saturated B. monounsaturated omega-3 C. monounsat urated omega-6

28 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Draw the condensed structural formulas for each of the fatty acids with 10 carbon atoms that follow. 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 C. monounsat urated omega-6

29 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Waxes and Triacylglycerols Chapter 17 Lipids Lectures

30 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Waxes Waxes are  esters of saturated fatty acids and long-chain alcohols each containing 14 to 30 carbon atoms.  coatings that prevent loss of water from leaves of plants.

31 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Typical Waxes

32 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Fats and Oils: Triacylglycerols Fats and oils are  also called triacylglycerols.  triesters of glycerol.  produced by esterification.  formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids.  a major form of energy storage for animals. Insert picture of polar bear pg 608

33 © 2013 Pearson Education, Inc. Chapter 17, Section 1 In a triacylglycerol, glycerol forms ester bonds with three fatty acids. Triacylglycerols Insert structure top pg 608 as shown:

34 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Formation of a Triacylglycerol  Most naturally occurring fats and oils are mixed triacylglycerols that contain glycerol bonded by ester bonds to two or three different fatty acids, typically palmitic acid, linoleic acid, and stearic acid.  One possible structure follows.

35 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check What are the fatty acids in the following triacylglycerol?

36 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Stearic acid Oleic acid Myristic acid

37 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Draw the condensed structural formula for glyceryl tripalmitoleate (tripalmitolein).

38 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Draw the condensed structural formula for glyceryl tripalmitoleate (tripalmitolein).

39 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Melting Points of Fats and Oils A triacylglycerol that is usually called a fat  is solid at room temperature.  is prevalent in meats, whole milk, butter, and cheese. A triacylglycerol that is usually called an oil  is liquid at room temperature.  is prevalent in plants, such as olive and safflower.

40 © 2013 Pearson Education, Inc. Chapter 17, Section 1 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 closely together as in fats.  have lower melting points than do saturated fats.  are liquids at room temperature.

41 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Triacylglycerol with Unsaturated Fatty Acids Unsaturated fatty acid chains have kinks that do not allow close packing, such as those in olive oil.

42 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Saturated and Unsaturated Fatty Acids In Fats and Oils Vegetable oils are liquids at room temperature because they have a higher percentage of unsaturated fatty acids than do animal fats.

43 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Chemical Properties of Triacylglycerols Chapter 17 Lipids Lectures

44 © 2013 Pearson Education, Inc. Chapter 17, Section 1 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. Chemical Properties of Triacylglycerols

45 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Hydrogenation of Glyceryl Trioleate In a hydrogenation reaction, H 2 adds across the double bond to form a carbon–carbon single bond.

46 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Hydrogenation of Oils The hydrogenation of oils  converts double bonds to single bonds,  adds hydrogen (H 2 ) to the carbon atoms of double bonds,  increases the melting point, and  produces solids, such as margarine and shortening

47 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Which of the following products is obtained from the complete hydrogenation of glyceryl trioleate? A. glycerol and 3 oleic acids B. glyceryltristearate C. glycerol and 3 stearic acids

48 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Which of the following products is obtained from the complete hydrogenation of glyceryl trioleate? B. glyceryltristearate Solution

49 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Olestra, a Fat Substitute Olestra is  used in foods as an artificial fat.  composed of 6–8 long-chain fatty acids attached by ester links to a sucrose (not glycerol) molecule.  not broken down in the intestinal tract.

50 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Unsaturated fatty acids can be  cis with bulky groups on the same side of, or  trans with bulky groups on opposite sides of. Cis and Trans Fatty Acids

51 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Trans Fatty Acids and Hydrogenation Trans fatty acids  are formed during hydrogenation when cis double bonds are converted to an undesirable side product with a trans double bond.  in the body behave like saturated fatty acids.  are estimated to make up 2–4% of our total calories. The American Heart Association recommends the use of soft margarine, which is only slightly hydrogenated and therefore has fewer trans fatty acids.

52 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Trans Fats In vegetable oils,  the unsaturated fats usually contain cis double bonds.  during hydrogenation, some cis double bonds are converted to trans double bonds (more stable), causing a change in the fatty acid structure.

53 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Formation of Trans Fats

54 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Identify each statement as true (T) or false (F). 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.

55 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Identify each statement as true (T) or false (F). T A. There are more unsaturated fats in vegetable oils. F B. Vegetable oils have higher melting points than fats. T C. Hydrogenation of oils converts some cis-double bonds to trans-double bonds. T D. Animal fats have more saturated fats.

56 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Hydrolysis In acid or enzyme hydrolysis,  water adds to the ester bonds.  triacylglycerols hydrolyze forming glycerol and three fatty acids.  a strong acid, such as HCl or H 2 SO 4, or an enzyme catalyst is required.

57 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Base Hydrolysis (Saponification ) In base hydrolysis (saponification),  a triacylglycerol reacts with heat and a strong base.  a triacylglycerol splits into glycerol and the salts of fatty acids (soap).  a solid soap that can be molded into a desired shape is produced when NaOH is used.  a softer, liquid soap is produced when KOH is used.  polyunsaturated oils produce softer soaps.

58 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Saponification glycerol + salts of fatty acids (soap)Fat or oil + strong base

59 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Summary of Organic and Lipid Reactions

60 © 2013 Pearson Education, Inc. Chapter 17, Section 1 What products are obtained from the complete hydrolysis of glyceryl trioleate? A. glycerol and 3 oleic acids B. glyceryl tristearate C. glycerol and 3 stearic acids Learning Check

61 © 2013 Pearson Education, Inc. Chapter 17, Section 1 What products are obtained from the complete hydrolysis of glyceryl trioleate? A. glycerol and 3 oleic acids Solution

62 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Draw the condensed structural formula of the product of the following reaction.

63 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution

64 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Phospholipids Chapter 17 Lipids Lectures

65 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Glycerophospholipids, the most abundant lipids in cell membranes, contain  two fatty acids, which form ester bonds with the first and second hydroxyl group of glycerol.  a third hydroxyl group, which forms an ester with phosphoric acid, which then forms another phosphoester bond with an amino alcohol. Glycerophospholipids Insert picture of glycerophospholipid pg 618

66 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Lecithin and cephalin are glycerophospholipids that  are abundant in brain and nerve tissues.  are found in egg yolk, wheat germ, and yeast.  contain choline (in lecithins) or either ethanolamine or serine (in cephalins). Lecithin and Cephalin

67 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Glycerophospholipids Contain Amino Alcohols.  Three amino alcohols found in glycerophospholipids are choline, serine, and ethanolamine.  In the body, at a physiological pH of 7.4, these amino alcohols are ionized. Insert structures of amino alcohols pg 618 bottom

68 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Glycerophospholipids are Polar and Nonpolar. Glycerophospholipids have  both polar and nonpolar regions that allow them to interact with polar and nonpolar substances.  an ionized amino alcohol and phosphate portion, called “the head,” which is polar and strongly attracted to water.  a hydrocarbon chain known as “the tail,” which is soluble in nonpolar substances.

69 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Formation of Glycerophospholipids The formation of a glycerophospholipid occurs when ester bonds form between glycerol and two fatty acids, and two phosphoester bonds form between phosphoric acid and an ionized amino alcohol and glycerol, such as palmitic acid.

70 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Components of Glycerophospholipids The components of a glycerophospholipid are choline, phosphoric acid, glycerol, and two fatty acids. Insert structure from figure 17.6a

71 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Components of Glycerophospholipids In a glycerophospholipid, a polar “head” contains the ionized amino alcohol and phosphate, while the hydrocarbon chains of two fatty acids make up the nonpolar “tails.” Insert structure from figure 17.6b

72 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Identify each as a fatty acid, triacylglycerol, amino alcohol or glycerophospholipid. A. glyceryl trioleate B. cephalin C. choline D. palmitic acid

73 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Identify each as a fatty acid, triacylglycerol, amino alcohol or glycerophospholipid. A. glyceryl trioleate triacylglycerol B. cephalinglycerophospholipid C. cholineamino alcohol D. palmitic acid fatty acid

74 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Identify the components and type of glycerophospholipid. O ║ CH 2 —O—C— (CH 2 ) 16 —CH 3 O ║ CH 2 —O—C— (CH 2 ) 16 —CH 3 + O NH 3 ║ │ CH 2 —O—P—O—CH 2 —CH−COO – │ O –

75 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Identify the components and type of glycerophospholipid. O ║ CH 2 —O—C— (CH 2 ) 16 —CH 3 O 2 Stearic acids ║ CH 2 —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

76 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Sphingosine Sphingosine is an 18-carbon unsaturated amino alcohol. Insert structure top pg 621

77 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Sphingolipids Sphingolipids are phospholipids that contain a long- chain amino alcohol called sphingosine, rather than glycerol.

78 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Sphingomyelins Sphingomyelins, are a group of sphingolipids in which  the amine group forms an amide bond to a fatty acid, and  the hydroxyl group of sphingosine forms an ester bond with phosphate forming another phosphoester bond to an amino alcohol, such as choline.

79 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Sphingomyelins Sphingomyelins, are abundant in the  white matter of the myelin sheath, a coating surrounding the nerve.  cells that increase the speed of nerve impulses and insulate and protect the nerve cells.

80 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Multiple Sclerosis In multiple sclerosis,  sphingomyelin is lost from the myelin sheath, which protects the neurons in the brain and spinal cord.  scars form on the neurons and impair the transmission of nerve signals.

81 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Steroids Chapter 17 Lipids Lectures

82 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Steroid Nucleus Steroid molecules contain a steroid nucleus with  3 cyclohexane rings,  1 cyclopentane ring,  no fatty acids, and  a total of four rings A, B, C, D. The steroid nucleus is numbered from the carbon atoms in ring A to two methyl groups at 18 and 19.

83 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Cholesterol  is the most important and abundant steroid in the body.  is a sterol because it contains an oxygen atom as a hydroxyl group, –OH on carbon 3.  has a double bond between carbon 5 and carbon 6.  has methyl –CH 3 groups, at carbon 10 and 13.  has a carbon chain at carbon 17.

84 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Cholesterol Cholesterol is a component of cellular membranes, myelin sheaths, and brain and nerve tissues.

85 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Cholesterol in the Body Cholesterol in the body  is obtained from meats, milk, and eggs and synthesized in the liver.  clogs arteries when high levels form plaque. A normal, open artery. An artery clogged by cholesterol plaque

86 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Cholesterol in Foods A typical American diet includes 400–500 mg of cholesterol per day. The American Heart Association has recommended no more than 300 mg of cholesterol per day. Saturated fats in the diet may stimulate the production of cholesterol by the liver.

87 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Match the components of the cholesterol molecule with each of the following: alkyl chain hydroxyl group steroid nucleus methyl group A C B D

88 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution Match the components of the cholesterol molecule with each of the following: alkyl chain hydroxyl group steroid nucleus methyl group A C B D D A C B

89 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Bile Salts Bile salts  are synthesized from cholesterol in the liver.  are stored in the gallbladder and secreted into the small intestine.  have a polar and a nonpolar region.  help in the absorption of cholesterol into the intestinal mucosa.

90 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Sodium Glycocholate, a Bile Salt Nonpolar region Polar region

91 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Gallstones Gallstones are  formed when large amounts of cholesterol accumulate in the gallbladder.  composed of almost 100% cholesterol, with some calcium salts, fatty acids, and glycerophospholipids.

92 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Lipoproteins  are spherical particles with an outer surface of polar proteins and glycerophospholipids that surround hundreds of nonpolar molecules of triacylglycerols and cholesteryl esters.  combine lipids with proteins and phospholipids.  are soluble in water because the surface consists of polar lipids.

93 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Lipoproteins A spherical lipoprotein particle surrounds nonpolar lipids with polar lipids and protein for transport to body cells.

94 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Types of Lipoproteins Lipoproteins differ in density, composition, and function and include  chylomicrons, very low-density lipoprotein (VLDLs);  low-density lipoproteins (LDLs), which carry cholesterol to the tissues; and  high-density lipoproteins (HDLs) that pick up cholesterol from the tissues and carry it to the liver.

95 © 2013 Pearson Education, Inc. Chapter 17, Section 1 LDLs  transport cholesterol to tissues where it can be used for synthesis of cell membranes and steroid hormones.  deposit cholesterol in the arteries in the form of plaque when cholesterol levels exceed levels needed by tissues.  called “bad” cholesterol for their contribution to heart disease.

96 © 2013 Pearson Education, Inc. Chapter 17, Section 1 HDLs  are more dense than LDLs due to the increased amount of protein present.  pick up cholesterol from the tissues and carry it to the liver, where it can be converted to bile salts, which are eliminated from the body,  are called “good” cholesterol.

97 © 2013 Pearson Education, Inc. Chapter 17, Section 1 VLDLs VLDLs carry the triacylglycerols synthesized in the liver to the adipose tissues for storage. Insert fig pg 626

98 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Lipid Panel A lipid panel is a blood test that measures serum lipid levels including  cholesterol  triglycerides  high-density lipoprotein (HDL)  low-density lipoprotein (LDL) The results of a lipid panel are used to evaluate a patient’s risk of heart disease.

99 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Lipid Panel

100 © 2013 Pearson Education, Inc. Chapter 17, Section 1 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.

101 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Steroid Hormones

102 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Adrenal Corticosteroids Adrenal corticosteroids are steroid hormones produced by the adrenal glands located on the top of each kidney and include  aldosterone, which regulates electrolytes and water balance by the kidneys;  cortisol, released under stress to increase blood sugar and regulate carbohydrate, fat, and protein metabolism; and  prednisone, a synthetic corticosteroid, derived from cortisone, used for reducing inflammation, treating asthma and rheumatoid arthritis.

103 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Adrenal Corticosteroids

104 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check Identify each of the following as a steroid, triacylglycerol, phospholipid, or sphingolipid. A. cholesterol B. glycerol, 2 fatty acids, phosphate, and choline C. glyceryl tristearate D. sphingosine, fatty acid, phosphate, and choline E. estradiol F. bile salts G. lipids in plasma membranes

105 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution A. cholesterolsteroid B. glycerol, 2 fatty acids,phospholipid phosphate, and choline C. glyceryl tristearatetriacylglycerol D. sphingosine, fatty acid, sphingolipid phosphate, and choline E. estradiolsteroid F. bile salts steroid G. lipids in plasma phospholipid membranessphingolipid

106 © 2013 Pearson Education, Inc. Chapter 17, Section 1 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake © 2013 Pearson Education, Inc Cell Membranes Chapter 17 Lipids Lectures

107 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Cell Membranes Cell membranes have a lipid bilayer that  separates cellular contents from the external environment.  contains two layers of glycerophospholipids arranged with their hydrophilic heads at the outer and inner membrane surfaces and their hydrophobic tails in the center.

108 © 2013 Pearson Education, Inc. Chapter 17, Section 1 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.

109 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Fluid Mosaic Model

110 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Transport Pathways Through Cell 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; and  active transport, which moves ions against a concentration gradient.

111 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Transport Pathways Through Cell Membranes

112 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Learning Check What is the transport of particles across a cell membrane from high concentration to low concentration called? A. facilitated transport B. diffusion (passive transport) C. active transport

113 © 2013 Pearson Education, Inc. Chapter 17, Section 1 Solution What is the transport of particles across a cell membrane from high concentration to low concentration called? A. facilitated transport B. diffusion (passive transport) C. active transport