1. Chapter 15 Lipids
15.1
Lipids
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2. 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.

3. Types of Lipids The types of lipids containing fatty acids are Waxes.
Fats and oils (triacylglycerols).
Glycerophospholipids.
Prostaglandins.
Not steroids, as they do not contain fatty acids.

4. Structures of Lipids Copyright © 2007 by Pearson Education, Inc.
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5. 15.2 Fatty Acids Copyright © 2007 by Pearson Education, Inc.
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6. Fatty Acids Fatty acids Are long-chain carboxylic acids.
Typically contain carbon atoms.
Are insoluble in water.
Can be saturated or unsaturated.
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7. Fatty Acid Formulas The formulas for fatty acids are written as
Condensed formulas.
Line-bond formulas.
For example caprylic acid with 8 carbon atoms.
CH3—(CH2)6—COOH
CH3—CH2—CH2—CH2—CH2—CH2—CH2—COOH

8. 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.
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9. Some Saturated Fatty Acids
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10. Unsaturated Fatty Acids
Have one or more double C=C bond
Typically contain cis double bonds.
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11. Properties of 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.
“kinks” in chain
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12. Unsaturated Fatty Acids
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13. Comparing Melting Points of Some Fatty Acids
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14. Learning Check stearic acid (18 C) saturated
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

15. 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

16. Prostaglandins Prostaglandins have
20 carbon atoms in their fatty acid chains.
An OH on carbon 11 and 15.
A trans double bond at carbon 13.
C 11
C 13
C 15
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17. Prostaglandins in the Body
Prostaglandins are
Produced by injured tissues.
Involved in pain, fever, and inflammation.
Not produced when anti-inflammatory drugs such as aspirin inhibit their synthesis.
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18. Omega-6 and Omega 3- Fatty Acids
In vegetable oils are mostly omega-6 with
the first C=C at C6.
linoleic acid
CH3─(CH2)4─CH=CH─CH2─CH=CH─(CH2)7─COOH 6
In fish oils are mostly omega-3 with the
first C=C at C3.
linolenic acid
CH3─CH2─(CH=CH─CH2)3─(CH2)6─COOH 3
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19. Some Omega-6 and Omega-3 Fatty Acids

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

21. Solution Write a fatty acid with 10 carbon atoms that is: A. saturated
CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—COOH
B. monounsaturated omega-3
CH3—CH2—CH=CH—CH2—CH2—CH2—CH2—CH2—COOH
C. monounsaturated omega-6
CH3—CH2—CH2—CH2—CH2—CH=CH—CH2—CH2—COOH

22. Waxes, Fats, and Oils Copyright © 2007 by Pearson Education, Inc.
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23. Waxes
Waxes are
Esters of saturated fatty acids and long-chain alcohols.
Coatings that prevent loss of water by leaves of plants.
TABLE 17.2
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24. Fats and Oils: 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.
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25. Triacylglycerols In a triacylglycerol,
Glycerol forms ester bonds with three fatty acids.
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26. Formation of a Triacylglycerol
glycerol three fatty acids triacylglycerol +
+ 3H2O

27. Olive Oil
Olive oil
Contains a high percentage of oleic acid, which is a monounsaturated fatty acid with one cis double bond.
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28. Learning Check
What are the fatty acids in the following triacylglycerol?

29. Solution
Stearic acid
Oleic acid
Myristic acid

30. Melting Points of Fats and Oils
A triacylglycerol that is a fat
Is solid at room temperature.
Is prevalent in meats, whole milk, butter, and cheese.
A triacylglycerol that is an oil
Is liquid at room temperature.
Is prevalent in plants such as olive and safflower.

31. Oils with Unsaturated Fatty Acids
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.

32. Diagram of Triacylglycerol with Unsaturated Fatty Acids
Unsaturated fatty acid chains have kinks that do not allow close packing.
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33. Saturated and Unsaturated Fatty Acids In Fats and Oils
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34. Chemical Properties of Triacylglycerols
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35. 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 H2 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 The hydrogenation of oils
Adds hydrogen (H2) to the carbon atoms of double bonds.
Converts double bonds to single bonds.
Increases the melting point.
Produces solids such as margarine and shortening.
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37. Hydrogenation Ni + 3H2 glyceryl tripalmitoleate glyceryl tripalmitate
(tripalmitolean)
glyceryl tripalmitate
(tripalmitin)

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

39. Solution What product(s) is obtained from the complete
hydrogenation of glyceryl trioleate?
2. Glyceryltristearate

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.
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41. Cis and Trans Fatty Acids
Unsaturated fatty acids can be
Cis with bulky groups on same side of C=C.
CH3─ (CH2)5 (CH2)7─ COOH cis
C=C
H H
Trans have bulky groups on opposite sides of C=C.
CH3─ (CH2)5 H
C=C trans
H (CH2)7─ COOH

42. Trans Fatty Acids and Hydrogenation
Are formed during hydrogenation when cis double bonds are converted to trans double bonds.
In the body behave like saturated fatty acids.
Are estimated to make up 2-4% of our total Calories.
Are reported in several studies reported to raise LDL-cholesterol and lower HDL-cholesterol.

43. Learning Check (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. Solution (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.
C. T Hydrogenation of oils converts some cis-double
bonds to trans- double bonds.
D. T Animal fats have more saturated fats.

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

46. Saponification and Soap
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 KOH gives softer soaps.

47. Saponification
+ 3NaOH + 3
“soap”

48. Learning Check 1. Glycerol and 3 oleic acids 2. Glyceryl tristearate
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

49. Solution
What products are obtained from the complete hydrolysis of glyceryl trioleate?
1. Glycerol and 3 oleic acids

50. Learning Check
Write the product of the following reaction.
+ 3

51. Solution

52. Glycerophospholipids
Glycerophospholipids are
The most abundant lipids in cell membranes.
Composed of glycerol, two fatty acids, phosphate and an amino alcohol.
Fatty acid
Glycerol
Fatty acid
PO4
Amino
alcohol

53. Glycerophospholipids Are Polar
A glycerophospholipid has
Two nonpolar fatty acid chains.
A phosphate group and a polar amino alcohol.
CH3 │
HO−CH2−CH2−N−CH HO−CH2−CH2−NH3 │
choline CH ethanolamine +
NH3
│ Amino alcohols
HO−CH2−CH−COO−
serine

54. Structure and Polarity of A Glycerophospholipid
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55. Lecithin and Cephalin Lecithin and cephalin are glycerophospholipids
Abundant in brain and nerve tissues.
Found in egg yolk, wheat germ, and yeast.
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56. Learning Check Identify each as a A. fatty acid B. triacylglycerol
C. amino alcohol D. glycerophospholipid
1. glyceryl trioleate
2. cephalin
3. choline
4. palmitic acid

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

58. Learning Check Identify the components and type of glycerophospholipid║
CH2−O −C −(CH2)16 −CH3 +
O NH3
║ │
CH2−O −P −O − CH2−CH−COO- │ O-

59. Solution Identify the components and type of glycerophospholipid O ║
CH2−O −C −(CH2)16 −CH3
O 2 stearic acids +
O NH3
║ │ type = cephalin
CH2−O −P −O − CH2−CH−COO-
│ serine O-
phosphate amino alcohol

60. Sphingolipids Copyright © 2007 by Pearson Education, Inc.
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61. Sphingolipids Sphingolipids Are similar to phospholipids.
Contain sphingosine (a long-chain amino alcohol), a fatty acid, phosphate, and a small amino alcohol.
Have polar and nonpolar regions.
fatty acid
sphingosine
PO4
amino
alcohol

62. Sphingosine Sphingosine is a long-chain unsaturated amino alcohol.
CH3−(CH2)12 −CH=CH−CH−OH │
CH−NH2
CH2−OH
sphingosine

63. Sphingolipids In sphingomyelin, a sphingolipid found in nerve cells
There is an amide bond between a fatty acid and sphingosine, an 18-carbon alcohol.
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64. Glycosphingolipids
Glycosphingolipids contain monosaccharides bonded to the –OH of sphingosine by a glycosidic bond.
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65. Glycosphingolipids and Cerebrosides
Are sphingolipids that contain monosaccharides.
Can be a cerebroside with galactose.
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66. Gangliosides Gangliosides
Are similar to cerebrosides, but contain two or more monosaccharides.
Are important in neurons.
Act as receptor for hormones and viruses.
Can accumulate and cause genetic diseases.

67. Gangliosides GM2 is a ganglioside
That accumulates in Tay-Sachs disease.
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68. Lipid Diseases (Lipidoses)
In many lipid diseases, the deficiency of an enzyme causes the accumulation of glycolipids.
TABLE 17.3
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69. Learning Check Identify each as a 1) Fatty acid 2) Triacylglycerol
3) Amino alcohol 4) Glycerophospholipid
5) Glycosphingolipid
A. Glyceryl trioleate
B. Cephalin
C. Choline
D. Galactocerebroside
E. Palmitic acid

70. Solution A. Glyceryl trioleate 2) Triacylglycerol
B. Cephalin 4) Glycerophospholipid
C. Choline 3) Amino alcohol
D. Galactocerebroside 5) Glycosphingolipid
E. Palmitic acid 1) Fatty acid

71. Steroids: Cholesterol, Bile Salts, and Steroid Hormones
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72. Steroid Nucleus A steroid nucleus consists of 3 cyclohexane rings.
1 cyclopentane ring.
No fatty acids.
steroid nucleus

73. Cholesterol Cholesterol Is the most abundant steroid in the body.
Has methyl CH3- groups, alkyl chain, and -OH attached to the steroid nucleus.

74. Cholesterol in the Body
A normal, open artery.
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.
An artery clogged by cholesterol plaque
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75. Cholesterol in Foods Cholesterol is Synthesized in the liver.
Obtained from foods.
Considered elevated if plasma cholesterol exceeds 200 mg/dL.
TABLE 17.4
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76. Learning Check Match the components of the cholesterol molecule with
the following:
___ carbon chain ___hydroxyl group
___ steroid nucleus ___methyl group D B A C

77. Solution Match the components of the cholesterol molecule with
the following:
D carbon chain A hydroxyl group
C steroid nucleus B methyl group D B A C

78. Bile Salts Bile salts Are synthesized in the liver from cholesterol.
Are stored in the gallbladder.
Are secreted into the small intestine.
Have a polar and a nonpolar region
Mix with fats to break them part.
Emulsify fat particles to provide large surface area.

79. Bile Salts
Polar region
Nonpolar region

80. Lipoproteins Lipoproteins
Combine lipids with proteins and phospholipids.
Are soluble in water because the surface consists of polar lipids.
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81. Types of Lipoproteins Lipoproteins
Differ in density, composition, and function.
Include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs).
TABLE 17.5
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82. Transport of Lipoproteins in the Body
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83. 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.
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84. Adrenal Corticosteroids
Adrenal corticosteroids are steroid hormones that
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.

85. Adrenal Corticosteroids
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86. 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.
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87. Learning Check Identify each as a
1. fatty acid 2. steroid triacylglycerol
4. phospholipid 5. 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

88. Solution A. cholesterol 2 steroid
B. glycerol, 2 fatty acids, phosphate, and choline
4 phospholipid
C. glyceryl tristearate triacylglycerol
D. sphingosine, fatty acid, phosphate, and choline
5 sphingolipid
E. estradiol 2 steroid
F. bile salts 2 steroid
G. lipids in plasma membranes
4 phospholipid, 5 sphingolipid .

89. Cell Membranes Copyright © 2007 by Pearson Education, Inc.
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90. 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.

91. 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.

92. Fluid Mosaic Model Copyright © 2007 by Pearson Education, Inc.
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93. Transport 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.
Active transport, which moves ions against a concentration gradient.

94. Transport Pathways Through Cell Membranes
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95. Learning Check The transport of particles across a cell membrane from
high concentration to low concentration is called
1. Facilitated transport
2. Diffusion
3. Active transport

96. Solution The transport of particles across a cell membrane from
high concentration to low concentration is called
2. Diffusion