2. 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. 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.
7. 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
OH
O
14. 14
Learning Check
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. 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
20. 20
Learning Check
Write a fatty acid with 10 carbon atoms that is:
A. saturated
B. monounsaturated omega-3
C. monounsaturated omega-6
21. 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
26. 26
Formation of a Triacylglycerol
glycerol + three fatty acids triacylglycerol
OH
CH2
OH
OH
CH2
CH
O
(CH2)14CH3
C
HO
O
(CH2)14CH3
C
HO
O
(CH2)14CH3
C
HO
+ 3H2O
O
O
C (CH2)14CH3
CH O
O
C (CH2)14CH3
CH2 O
O
C (CH2)14CH3
CH2
+
28. 28
Learning Check
What are the fatty acids in the following triacylglycerol?
(CH2)12CH3
O
C
CH(CH2)7CH3
(CH2)7CH
O
C
O
(CH2)16CH3
C
O
O
O
CH2
CH2
CH
30. 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. 31
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.
35. 35
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.
Chemical Properties of
Triacylglycerols
38. 38
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
Learning Check
39. 39
What product(s) is obtained from the complete
hydrogenation of glyceryl trioleate?
2. Glyceryltristearate
Solution
41. 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. 42
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 2-4% of our total
Calories.
Are reported in several studies reported to raise
LDL-cholesterol and lower HDL-cholesterol.
43. 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. 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. 45
Hydrolysis
In hydrolysis,
Triacylglycerols split into glycerol and three fatty acids.
An acid or enzyme catalyst is required.
O
CH2
O
CH
O
CH2
OH
CH2
OH
CH
OH
CH2 O
(CH2)14CH3
C
HO
H2O
O
(CH2)14CH3
C
O
(CH2)14CH3
C
O
(CH2)14CH3
C
H+
+3
+ 3
46. 46
Saponification and Soap
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 KOH gives softer soaps.
48. 48
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
Learning Check
49. 49
What products are obtained from the complete
hydrolysis of glyceryl trioleate?
1. Glycerol and 3 oleic acids
Solution
50. 50
Learning Check
Write the product of the following reaction.
O
CH2
O
O
CH2
CH
CH(CH2)7CH3
(CH2)5CH
O
C
O
CH(CH2)7CH3
(CH2)5CH
C
O
C CH(CH2)7CH3
(CH2)5CH
H2
Ni
+ 3
52. 52
Glycerophospholipids are
The most abundant lipids in cell membranes.
Composed of glycerol, two fatty acids, phosphate
and an amino alcohol.
Glycerol
PO4
Amino
alcohol
Glycerophospholipids
Fatty acid
Fatty acid
53. 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−CH3 HO−CH2−CH2−NH3
│
choline CH3 ethanolamine
+
NH3
│ Amino alcohols
HO−CH2−CH−COO−
serine
56. 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. 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. 58
Learning Check
Identify the components and type of glycerophospholipid
O
║
CH2−O −C −(CH2)16 −CH3
O
║
CH2−O −C −(CH2)16 −CH3
+
O NH3
║ │
CH2−O −P −O − CH2−CH−COO-
│
O-
59. 59
Solution
Identify the components and type of glycerophospholipid
O
║
CH2−O −C −(CH2)16 −CH3
O 2 stearic acids
║
CH2−O −C −(CH2)16 −CH3
+
O NH3
║ │ type = cephalin
CH2−O −P −O − CH2−CH−COO-
│ serine
O-
phosphate amino alcohol
61. 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.
sphingosine
PO4
amino
alcohol
fatty acid
62. 62
Sphingosine
Sphingosine is a long-chain unsaturated amino alcohol.
CH3−(CH2)12 −CH=CH−CH−OH
│
CH−NH2
│
CH2−OH
sphingosine
66. 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.
69. 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. 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
72. 72
Steroid Nucleus
A steroid nucleus consists of
3 cyclohexane rings.
1 cyclopentane ring.
No fatty acids.
steroid nucleus
73. 73
Cholesterol
Cholesterol
Is the most abundant steroid in the body.
Has methyl CH3- groups, alkyl chain, and -OH
attached to the steroid nucleus.
CH3
CH3
CH3
CH3
HO
CH3
76. 76
Learning Check
Match the components of the cholesterol molecule with
the following:
___ carbon chain ___hydroxyl group
___ steroid nucleus ___methyl group
CH3
CH3
CH3
CH3
HO
CH3
A
C
B
D
77. 77
Solution
Match the components of the cholesterol molecule with
the following:
D carbon chain A hydroxyl group
C steroid nucleus B methyl group
CH3
CH3
CH3
CH3
HO
CH3
A
C
B
D
78. 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.
84. 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.
87. 87
Learning Check
Identify each as a
1. fatty acid 2. steroid 3. 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. 88
Solution
A. cholesterol 2 steroid
B. glycerol, 2 fatty acids, phosphate, and choline
4 phospholipid
C. glyceryl tristearate 3 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
.
90. 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. 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.
93. 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.
95. 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. 96
Solution
The transport of particles across a cell membrane from
high concentration to low concentration is called
2. Diffusion