1. Chapter 17 Lipids
17.1 Lipids
Describe the classes of lipids.

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 lipids that contain fatty acids are: waxes
fats and oils (triacylglycerols)
glycerophospholipids
prostaglandins
The types of lipids that do not contain fatty acids are
steroids

5. Chapter 17 Lipids 17.2 Fatty Acids Write the condensed
structural formula of
a fatty acid and identify
it as saturated or
unsaturated.

6. Fatty Acids Fatty acids are long-chain carboxylic acids
typically contain 12 to 18 carbon atoms
are insoluble in water
can be saturated or unsaturated

7. Fatty Acid Formulas The formulas for fatty acids are written as
condensed structural formulas
line-bond formulas

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

9. Some Saturated Fatty Acids

10. Unsaturated Fatty Acids
have one or more double C═C bond
typically contain cis double bonds

11. Some Unsaturated Fatty Acids

12. Properties of 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

13. Prostaglandins Prostaglandins have
20 carbon atoms in their fatty acid chains
an OH on carbons 11 and 15
a trans double bond at carbon 13
C11
C15
C13

14. 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

15. Omega-6 and Omega-3 Fatty Acids
H.N: P 610
Omega-6 and Omega-3 Fatty Acids
Fatty acids
in vegetable oils are mostly omega-6 with
the first C═C at C6
CH3─(CH2)4─CH═CH─CH2─CH═CH─(CH2)7─COOH
Linoleic acid
in fish oils are mostly omega-3 with the first C═C at C3
CH3─CH2─(CH═CH─CH2)3─(CH2)6─COOH
Linolenic acid

16. Some Omega-6 and Omega-3 Fatty Acids

17. Chapter 17 Lipids 17.3 Waxes, Fats, and Oils
Write the structural formula of a wax, fat, or oil produced by the
reaction of a fatty acid and an alcohol or glycerol.

18. Waxes
Waxes are
esters of saturated fatty acids and long-chain alcohols
coatings that prevent loss of water from leaves of plants

19. 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

20. Triacylglycerols In a triacylglycerol,
glycerol forms ester bonds with three fatty acids

21. Formation of a Triacylglycerol
Glycerol and three stearic acid molecules form a
triacylglycerol named
glyceryl tristearate
tristearin

22. Formation of a Triacylglycerol
Source of energy for
hibernating animals.
Mixed triacylglycerol

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

24. 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

25. 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 do saturated fats
are liquids at room temperature

26. Diagram of Triacylglycerol with Unsaturated Fatty Acids
Unsaturated fatty acid chains have kinks that do not allow close packing.

27. Saturated and Unsaturated Fatty Acids In Fats and Oils
Triglycerols

28. 17.4 Chemical Properties of Triacylglycerols
Chapter 17 Lipids
17.4 Chemical Properties of Triacylglycerols
Draw the structure of the product when a triacylglycerol is
hydrogenated, hydrolyzed, or oxidized.

29. 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.

30. Hydrogenation of Glyceryl Trioleate

31. Hydrogenation of Oils The hydrogenation of oils
converts double bonds to single bonds
adds hydrogen (H2) to the carbon atoms of double bonds
increases the melting point
produces solids such as margarine and shortening

32. Oxidation of unsaturated fats
The fat or oil become rancid when oxidized.
The product is aldehyde. ( disagreeable odor)
Vegetable oil should contain antioxidant.
Oxidation also occurs in the oils present on the skin during heavy exercise.

33. Olestra, A Fat Substitute
H.N: P 616
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

34. Cis and Trans Fatty Acids
Unsaturated fatty acids can be
Cis with bulky groups on the same side of C═C
Trans have bulky groups on opposite sides of C═C

35. Trans Fatty Acids and Hydrogenation
H.N: P 617
Trans Fatty Acids and Hydrogenation
Trans fatty acids
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 to 4% of our total calories
in several studies are reported to raise LDL-cholesterol and lower HDL-cholesterol

36. 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
a label states “partially” or “fully hydrogenated” if the fats contain trans fatty acids

37. Formation of Trans Fats

38. 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.

39. 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.

40. Hydrolysis In acid or enzyme hydrolysis, water adds to the ester bonds
triacylglycerols split into glycerol and three fatty acids
an acid or enzyme catalyst is required

41. Base Hydrolysis (Saponification )
In base hydrolysis (saponification),
a triacylglycerol reacts with a strong base
a triacylglycerol splits into glycerol and the salts of fatty acids
soaps (salts of fatty acids) form

42. Saponification

43. 17.5 Glycerophospholipids
Chapter 17 Lipids
17.5 Glycerophospholipids
Describe the characteristics of glycerophospholipids

44. Glycerophospholipids
Glycerophospholipids are
the most abundant lipids in cell membranes
composed of glycerol, two fatty acids, phosphate, and an amino alcohol

45. Glycerophospholipids Are Polar
A glycerophospholipid has
two nonpolar fatty acid chains
a phosphate group
one of three polar amino alcohols

46. Structure and Polarity of a Glycerophospholipid

47. Structure and Polarity of a Glycerophospholipid
A glycerophospholipid has
Amine and phosphate called polar head
two fatty acid chains are called non-polar tail
Found in cell membrane (cellular permeability)
Present in myelin sheath of nerve
Help in the transport of TG and Cholesterol

48. Lecithin and Cephalin
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)
Phospholipids – P 624

49. Learning Check Identify each as a 1) fatty acid 2) triacylglycerol
3) amino alcohol 4) glycerophospholipid
A. Glyceryl trioleate
B. Cephalin
C. Choline
D. Palmitic acid

50. Solution Identify each as a 1) fatty acid 2) triacylglycerol
3) amino alcohol 4) glycerophospholipid
A. Glyceryl trioleate ) triacylglycerol
B. Cephalin 4) glycerophospholipid
C. Choline 3) amino alcohol
D. Palmitic acid 1) fatty acid

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

52. Solution Identify the components and type of glycerophospholipid: O ║
CH2—O—C— (CH2)16—CH3
O Stearic acids +
O NH3
║ │ Type = cephalin
CH2—O—P—O—CH2—CH−COO –
│ Serine
O– Phosphate Amino alcohol

53. 17.7 Steroids: Cholesterol, Bile Salts, and Steroid Hormones
Chapter 17 Lipids
17.7 Steroids: Cholesterol, Bile Salts, and Steroid Hormones
Describe the structures of steroids.

54. Steroid Nucleus A steroid nucleus has 3 cyclohexane rings
has 1 cyclopentane ring
contains no fatty acids
has four rings A, B, C, and D
is numbered from the carbon atoms in ring A to two methyl groups at 18 and 19

55. Cholesterol Cholesterol is the most abundant steroid in the body
has methyl CH3-groups, an alkyl chain, and —OH attached to the steroid nucleus

56. 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

57. Cholesterol in Foods Cholesterol is synthesized in the liver
obtained from foods
considered elevated if plasma cholesterol exceeds 200 mg/dL

58. Learning Check Match the components of the cholesterol molecule with
each of the following:
___ alkyl chain ___ hydroxyl group
___ steroid nucleus ___ methyl group D B A C

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

60. 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

61. Sodium Glycocholate, a Bile Salt
Polar region
Nonpolar region

62. Lipoproteins Lipoproteins
combine lipids with proteins and phospholipids
are soluble in water because the surface consists of polar lipids

63. Types of Lipoproteins Lipoproteins
differ in density, composition, and function
include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs)

64. Transport of Lipoproteins in the Body

65. 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

66. Transport of Lipoproteins in the Body
Chylomicrons and VLDL transport TG, PL, CHLO, to tissue for storage or muscle for energy.
LDL transport CHLO to tissue for synthesis of cell membrane, hormones and bile salts.
High level of LDL cause heart disease (MI)
HDL remove excess CHLO from tissue to liver for elimination
LDL & HDL are part of medical examination

67. Steroid Hormones (continued)

68. 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

69. Adrenal Corticosteroids (continued)

70. Anabolic Steroids Anabolic steroids are derivatives of testosterone
H.N. –P 632
Anabolic Steroids
Anabolic steroids
are derivatives of testosterone
are used illegally to increase muscle mass
have side effects that include fluid retention, hair growth, sleep disturbance, and liver damage

71. 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

72. Solution
A. Cholesterol 2) steroid B. Glycerol, 2 fatty acids, 4) phospholipid phosphate, and choline C. Glyceryl tristearate 3) triacylglycerol D. Sphingosine, fatty acid, 5) sphingolipid E. Estradiol 2) steroid F. Bile salts 2) steroid G. Lipids in plasma 4) phospholipid, membranes 5) sphingolipid