Biology in Focus Chapter 3

Chapter 3 - Carbon and the Molecular Diversity of Life

1. CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
3
Carbon and
the Molecular
Diversity of Life

2. Overview: Carbon Compounds and Life
Aside from water, living organisms consist mostly
of carbon-based compounds
Carbon is unparalleled in its ability to form large,
complex, and diverse molecules
A compound containing carbon is said to be an
organic compound
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3. Critically important molecules of all living things fall
into four main classes
Carbohydrates
Lipids
Proteins
Nucleic acids
The first three of these can form huge molecules
called macromolecules
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4. © 2014 Pearson Education, Inc.
Figure 3.1

5. Concept 3.1: Carbon atoms can form diverse
molecules by bonding to four other atoms
An atom’s electron configuration determines the
kinds and number of bonds the atom will form with
other atoms
This is the source of carbon’s versatility
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6. The Formation of Bonds with Carbon
With four valence electrons, carbon can form four
covalent bonds with a variety of atoms
This ability makes large, complex molecules
possible
In molecules with multiple carbons, each carbon
bonded to four other atoms has a tetrahedral shape
However, when two carbon atoms are joined by a
double bond, the atoms joined to the carbons are in
the same plane as the carbons
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7. When a carbon atom forms four single covalent
bonds, the bonds angle toward the corners of an
imaginary tetrahedron
When two carbon atoms are joined by a double bond,
the atoms joined to those carbons are in the same
plane as the carbons
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8. © 2014 Pearson Education, Inc.
Figure 3.2
Methane
Structural
Formula
Molecular
Formula
Space-Filling
Model
Ball-and-Stick
Model
Name
Ethane
Ethene
(ethylene)

9. The electron configuration of carbon gives it covalent
compatibility with many different elements
The valences of carbon and its most frequent
partners (hydrogen, oxygen, and nitrogen) are the
“building code” that governs the architecture of living
molecules
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10. © 2014 Pearson Education, Inc.
Figure 3.3
Hydrogen
(valence = 1)
Carbon
(valence = 4)
Nitrogen
(valence = 3)
Oxygen
(valence = 2)

11. Carbon atoms can partner with atoms other than
hydrogen; for example:
Carbon dioxide: CO
2
Urea: CO(NH
2
)
2
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12. © 2014 Pearson Education, Inc.
Figure 3.UN01
Estradiol
Testosterone

13. Molecular Diversity Arising from Variation in
Carbon Skeletons
Carbon chains form the skeletons of most organic
molecules
Carbon chains vary in length and shape
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Animation: Carbon Skeletons

14. © 2014 Pearson Education, Inc.
Figure 3.4
(a) Length
(b) Branching
(c) Double bond position
(d) Presence of rings
Ethane Propane
Butane BenzeneCyclohexane
1-Butene 2-Butene
2-Methylpropane
(isobutane)

15. © 2014 Pearson Education, Inc.
Figure 3.4a
(a) Length
Ethane Propane

16. © 2014 Pearson Education, Inc.
Figure 3.4b
(b) Branching
Butane 2-Methylpropane
(isobutane)

17. © 2014 Pearson Education, Inc.
Figure 3.4c
(c) Double bond position
1-Butene 2-Butene

18. © 2014 Pearson Education, Inc.
Figure 3.4d
(d) Presence of rings
BenzeneCyclohexane

19. Hydrocarbons are organic molecules consisting
of only carbon and hydrogen
Many organic molecules, such as fats, have
hydrocarbon components
Hydrocarbons can undergo reactions that release
a large amount of energy
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20. The Chemical Groups Most Important to Life
Functional groups are the components of organic
molecules that are most commonly involved in
chemical reactions
The number and arrangement of functional groups
give each molecule its unique properties
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21. The seven functional groups that are most important
in the chemistry of life:
Hydroxyl group
Carbonyl group
Carboxyl group
Amino group
Sulfhydryl group
Phosphate group
Methyl group
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22. © 2014 Pearson Education, Inc.
Figure 3.5
Chemical Group
Hydroxyl group ( OH)
Compound Name Examples
Alcohol
Ketone
Aldehyde
Methylated
compound
Organic
phosphate
Thiol
Amine
Carboxylic acid,
or organic acid
Ethanol
Acetone Propanal
Acetic acid
Glycine
Cysteine
Glycerol
phosphate
5-Methyl cytosine
Amino group ( NH
2
)
Carboxyl group ( COOH)
Sulfhydryl group ( SH)
Phosphate group ( OPO
3
2–
)
Methyl group ( CH
3
)
Carbonyl group ( C O)

23. © 2014 Pearson Education, Inc.
Figure 3.5a
Chemical Group
Hydroxyl group ( OH)
Compound Name Examples
Alcohol
Ketone
Aldehyde
Amine
Carboxylic acid,
or organic acid
Ethanol
Acetone Propanal
Acetic acid
Glycine
Amino group ( NH
2)
Carboxyl group ( COOH)
Carbonyl group ( C O)

24. © 2014 Pearson Education, Inc.
Figure 3.5aa
Hydroxyl group ( OH)
Alcohol
(The specific name
usually ends in -ol.)
Ethanol, the alcohol present
in alcoholic beverages
(may be written HO )

25. © 2014 Pearson Education, Inc.
Figure 3.5ab
Carbonyl group ( C O)
Ketone if the carbonyl
group is within a carbon
skeleton
Acetone, the simplest ketone
Aldehyde if the carbonyl
group is at the end of a
carbon skeleton
Propanal, an aldehyde

26. © 2014 Pearson Education, Inc.
Figure 3.5ac
Carboxyl group ( COOH)
Acetic acid, which gives
vinegar its sour taste
Carboxylic acid, or
organic acid
Ionized form of COOH
(carboxylate ion),
found in cells

27. © 2014 Pearson Education, Inc.
Figure 3.5ad
Amino group ( NH
2
)
Glycine, an amino acid
(note its carboxyl group)
Amine
Ionized form of NH
2
found in cells

28. © 2014 Pearson Education, Inc.
Figure 3.5b
Methylated
compound
Organic
phosphate
Thiol Cysteine
Glycerol
phosphate
5-Methyl cytosine
Sulfhydryl group ( SH)
Phosphate group ( OPO
3
2–
)
Methyl group ( CH
3)
Chemical Group Compound Name Examples

29. © 2014 Pearson Education, Inc.
Figure 3.5ba
Sulfhydryl group ( SH)
Cysteine, a sulfur-
containing amino acid
Thiol
(may be written HS )

30. © 2014 Pearson Education, Inc.
Figure 3.5bb
Phosphate group ( OPO
3
2–
)
Organic phosphate
Glycerol phosphate, which
takes part in many important
chemical reactions in cells

31. © 2014 Pearson Education, Inc.
Figure 3.5bc
Methyl group ( CH
3
)
Methylated compound
5-Methyl cytosine, a
component of DNA that has
been modified by addition of
a methyl group

32. ATP: An Important Source of Energy for Cellular
Processes
One organic phosphate molecule, adenosine
triphosphate (ATP), is the primary energy-
transferring molecule in the cell
ATP consists of an organic molecule called
adenosine attached to a string of three phosphate
groups
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33. © 2014 Pearson Education, Inc.
Figure 3.UN02
Adenosine

34. © 2014 Pearson Education, Inc.
Figure 3.UN03
Adenosine Adenosine
ATP Inorganic
phosphate
Energy
Reacts
with H
2
O
ADP

35. Concept 3.2: Macromolecules are polymers, built
from monomers
A polymer is a long molecule consisting of many
similar building blocks
These small building-block molecules are called
monomers
Some molecules that serve as monomers also have
other functions of their own
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36. Cells make and break down polymers by the same
process
A dehydration reaction occurs when two monomers
bond together through the loss of a water molecule
Polymers are disassembled to monomers by
hydrolysis, a reaction that is essentially the reverse
of the dehydration reaction
These processes are facilitated by enzymes, which
speed up chemical reactions
The Synthesis and Breakdown of Polymers
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Animation: Polymers

37. © 2014 Pearson Education, Inc.
Figure 3.6
Unlinked monomerShort polymer
Longer polymer
(a) Dehydration reaction: synthesizing a polymer
(b) Hydrolysis: breaking down a polymer

38. © 2014 Pearson Education, Inc.
Figure 3.6a
Unlinked monomerShort polymer
Longer polymer
(a) Dehydration reaction: synthesizing a polymer
Dehydration removes
a water molecule,
forming a new bond.

39. © 2014 Pearson Education, Inc.
Figure 3.6b
(b) Hydrolysis: breaking down a polymer
Hydrolysis adds
a water molecule,
breaking a bond.

40. The Diversity of Polymers
Each cell has thousands of different macromolecules
Macromolecules vary among cells of an organism,
vary more within a species, and vary even more
between species
An immense variety of polymers can be built from a
small set of monomers
HO
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41. Concept 3.3: Carbohydrates serve as fuel and
building material
Carbohydrates include sugars and the polymers of
sugars
The simplest carbohydrates are monosaccharides,
or simple sugars
Carbohydrate macromolecules are polysaccharides,
polymers composed of many sugar building blocks
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42. Sugars
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Monosaccharides have molecular formulas that
are usually multiples of CH
2
O
Glucose (C
6
H
12
O
6
) is the most common
monosaccharide
Monosaccharides are classified by the number of
carbons in the carbon skeleton and the placement
of the carbonyl group

43. © 2014 Pearson Education, Inc.
Figure 3.7
Glyceraldehyde
An initial breakdown
product of glucose in cells
Ribose
A component of RNA
Triose: 3-carbon sugar (C
3
H
6
O
3
) Pentose: 5-carbon sugar (C
5
H
10
O
5
)
Hexoses: 6-carbon sugars (C
6
H
12
O
6
)
Energy sources for organisms
Glucose Fructose

44. © 2014 Pearson Education, Inc.
Figure 3.7a
Glyceraldehyde
An initial breakdown
product of glucose in cells
Triose: 3-carbon sugar (C
3
H
6
O
3
)

45. © 2014 Pearson Education, Inc.
Figure 3.7b
Ribose
A component of RNA
Pentose: 5-carbon sugar (C
5
H
10
O
5
)

46. © 2014 Pearson Education, Inc.
Figure 3.7c
Hexoses: 6-carbon sugars (C
6
H
12
O
6
)
Energy sources for organisms
Glucose Fructose

47. Though often drawn as linear skeletons, in aqueous
solutions many sugars form rings
Monosaccharides serve as a major fuel for cells and
as raw material for building molecules
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48. © 2014 Pearson Education, Inc.
Figure 3.8
(a) Linear and ring forms
(b) Abbreviated ring structure

49. A disaccharide is formed when a dehydration
reaction joins two monosaccharides
This covalent bond is called a glycosidic linkage
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Animation: Disaccharides

50. © 2014 Pearson Education, Inc.
Figure 3.9-1
Glucose Fructose

51. © 2014 Pearson Education, Inc.
Figure 3.9-2
1–2
glycosidic
linkage
Glucose
Sucrose
Fructose

52. Polysaccharides
Polysaccharides, the polymers of sugars, have
storage and structural roles
The structure and function of a polysaccharide are
determined by its sugar monomers and the positions
of glycosidic linkages
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53. Storage Polysaccharides
Starch, a storage polysaccharide of plants, consists
entirely of glucose monomers
Plants store surplus starch as granules
The simplest form of starch is amylose
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54. Glycogen is a storage polysaccharide in animals
Humans and other vertebrates store glycogen
mainly in liver and muscle cells
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Animation: Polysaccharides

55. © 2014 Pearson Education, Inc.
Figure 3.10
Starch granules
in a potato tuber cell
Cellulose microfibrils
in a plant cell wall
Glycogen granules
in muscle
tissue
Cellulose
molecules
Hydrogen bonds
between —OH groups
(not shown) attached to
carbons 3 and 6
Starch (amylose)
Glycogen
Cellulose
Glucose
monomer

56. © 2014 Pearson Education, Inc.
Figure 3.10a
Starch granules
in a potato tuber cell
Starch (amylose)
Glucose
monomer

57. © 2014 Pearson Education, Inc.
Figure 3.10aa
Starch granules
in a potato
tuber cell

58. © 2014 Pearson Education, Inc.
Figure 3.10b
Glycogen granules
in muscle
tissue
Glycogen

59. © 2014 Pearson Education, Inc.
Figure 3.10ba
Glycogen
granules
in muscle
tissue

60. © 2014 Pearson Education, Inc.
Figure 3.10c
Cellulose microfibrils
in a plant cell wall
Cellulose
molecules
Hydrogen bonds
between —OH
groups on
carbons 3 and 6
Cellulose

61. © 2014 Pearson Education, Inc.
Figure 3.10ca
Cellulose
microfibrils
in a plant
cell wall

62. Structural Polysaccharides
The polysaccharide cellulose is a major component
of the tough wall of plant cells
Like starch and glycogen, cellulose is a polymer of
glucose, but the glycosidic linkages in cellulose differ
The difference is based on two ring forms for
glucose
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63. © 2014 Pearson Education, Inc.
Figure 3.11
(c) Cellulose: 1–4 linkage of b glucose monomers
(b) Starch: 1–4 linkage of a glucose monomers
(a) a and b glucose
ring structures
a Glucose b Glucose

64. © 2014 Pearson Education, Inc.
Figure 3.11a
(a) a and b glucose
ring structures
a Glucose b Glucose

65. In starch, the glucose monomers are arranged in
the alpha (a) conformation
Starch (and glycogen) are largely helical
In cellulose, the monomers are arranged in the beta
(b) conformation
Cellulose molecules are relatively straight
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66. © 2014 Pearson Education, Inc.
Figure 3.11b
(b) Starch: 1–4 linkage of a glucose monomers

67. © 2014 Pearson Education, Inc.
Figure 3.11c
(c) Cellulose: 1–4 linkage of b glucose monomers

68. In straight structures (cellulose), H atoms on one
strand can form hydrogen bonds with OH groups on
other strands
Parallel cellulose molecules held together this way
are grouped into microfibrils, which form strong
building materials for plants
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69. Enzymes that digest starch by hydrolyzing a linkages
can’t hydrolyze b linkages in cellulose
Cellulose in human food passes through the
digestive tract as insoluble fiber
Some microbes use enzymes to digest cellulose
Many herbivores, from cows to termites, have
symbiotic relationships with these microbes
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70. Chitin, another structural polysaccharide, is found in
the exoskeleton of arthropods
Chitin also provides structural support for the cell
walls of many fungi
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71. Concept 3.4: Lipids are a diverse group of
hydrophobic molecules
Lipids do not form true polymers
The unifying feature of lipids is having little or no
affinity for water
Lipids are hydrophobic because they consist mostly
of hydrocarbons, which form nonpolar covalent bonds
The most biologically important lipids are fats,
phospholipids, and steroids
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72. Fats
Fats are constructed from two types of smaller
molecules: glycerol and fatty acids
Glycerol is a three-carbon alcohol with a hydroxyl
group attached to each carbon
A fatty acid consists of a carboxyl group attached
to a long carbon skeleton
© 2014 Pearson Education, Inc.
Animation: Fats

73. © 2014 Pearson Education, Inc.
Figure 3.12
(b) Fat molecule (triacylglycerol)
Glycerol
(a) One of three dehydration reactions in the synthesis of a fat
Ester linkage
Fatty acid
(in this case, palmitic acid)

74. © 2014 Pearson Education, Inc.
Figure 3.12a
Glycerol
(a) One of three dehydration reactions in the synthesis of a fat
Fatty acid
(in this case, palmitic acid)

75. Fats separate from water because water molecules
hydrogen-bond to each other and exclude the fats
In a fat, three fatty acids are joined to glycerol by an
ester linkage, creating a triacylglycerol, or
triglyceride
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76. © 2014 Pearson Education, Inc.
Figure 3.12b
(b) Fat molecule (triacylglycerol)
Ester linkage

77. Fatty acids vary in length (number of carbons) and
in the number and locations of double bonds
Saturated fatty acids have the maximum number
of hydrogen atoms possible and no double bonds
Unsaturated fatty acids have one or more double
bonds
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78. © 2014 Pearson Education, Inc.
Figure 3.13
(a) Saturated fat (b) Unsaturated fat
Structural
formula of a
saturated fat
molecule
Structural
formula
of an
unsaturated
fat molecule
Space-filling
model of
stearic acid,
a saturated
fatty acid
Space-filling
model of oleic
acid, an
unsaturated
fatty acid Double bond
causes bending.

79. © 2014 Pearson Education, Inc.
Figure 3.13a
(a) Saturated fat
Structural
formula of a
saturated fat
molecule
Space-filling
model of
stearic acid,
a saturated
fatty acid

80. © 2014 Pearson Education, Inc.
Figure 3.13aa

81. © 2014 Pearson Education, Inc.
Figure 3.13b
(b) Unsaturated fat
Structural
formula
of an
unsaturated
fat molecule
Space-filling
model of
oleic acid, an
unsaturated
fatty acid Double bond
causes bending.

82. © 2014 Pearson Education, Inc.
Figure 3.13ba

83. Fats made from saturated fatty acids are called
saturated fats and are solid at room temperature
Most animal fats are saturated
Fats made from unsaturated fatty acids, called
unsaturated fats or oils, are liquid at room
temperature
Plant fats and fish fats are usually unsaturated
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84. The major function of fats is energy storage
Fat is a compact way for animals to carry their
energy stores with them
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85. Phospholipids
In a phospholipid, two fatty acids and a phosphate
group are attached to glycerol
The two fatty acid tails are hydrophobic, but the
phosphate group and its attachments form a
hydrophilic head
Phospholipids are major constituents of cell
membranes
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86. © 2014 Pearson Education, Inc.
Figure 3.14
(a) Structural formula (b) Space-filling model
Hydrophilic
head
(d) Phospholipid
bilayer
(c) Phospholipid
symbol
Hydrophobic
tails
Choline
Phosphate
Glycerol
Fatty acids
H
y
d
r
o
p
h
i
l
i
c

h
e
a
d
H
y
d
r
o
p
h
o
b
i
c

t
a
i
l
s

87. © 2014 Pearson Education, Inc.
Figure 3.14ab
(a) Structural formula (b) Space-filling model
Choline
Phosphate
Glycerol
Fatty acids
H
y
d
r
o
p
h
i
l
i
c

h
e
a
d
H
y
d
r
o
p
h
o
b
i
c

t
a
i
l
s

88. When phospholipids are added to water, they self-
assemble into a bilayer, with the hydrophobic tails
pointing toward the interior
This feature of phospholipids results in the bilayer
arrangement found in cell membranes
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89. © 2014 Pearson Education, Inc.
Figure 3.14cd
Hydrophilic
head
(d) Phospholipid
bilayer
(c) Phospholipid
symbol
Hydrophobic
tails

90. Steroids
Steroids are lipids characterized by a carbon
skeleton consisting of four fused rings
Cholesterol, an important steroid, is a component in
animal cell membranes
Although cholesterol is essential in animals, high
levels in the blood may contribute to cardiovascular
disease
© 2014 Pearson Education, Inc.
Video: Cholesterol Stick Model
Video: Cholesterol Space Model

91. © 2014 Pearson Education, Inc.
Figure 3.15

92. Concept 3.5: Proteins include a diversity of
structures, resulting in a wide range of functions
Proteins account for more than 50% of the dry mass
of most cells
Protein functions include defense, storage,
transport, cellular communication, movement, and
structural support
© 2014 Pearson Education, Inc.
Animation: Contractile Proteins
Animation: Defensive Proteins
Animation: Enzymes

93. © 2014 Pearson Education, Inc.
Animation: Gene Regulatory Proteins
Animation: Hormonal Proteins
Animation: Receptor Proteins
Animation: Sensory Proteins
Animation: Storage Proteins
Animation: Structural Proteins
Animation: Transport Proteins

94. © 2014 Pearson Education, Inc.
Figure 3.16
Enzymatic proteins
Storage proteins
Hormonal proteins
Contractile and motor proteins
Defensive proteins
Transport proteins
Receptor proteins
Structural proteins
Enzyme
Function: Selective acceleration of chemical reactions
Function: Storage of amino acids
Example: Digestive enzymes catalyze the hydrolysis of bonds in food
molecules.
Ovalbumin Amino acids
for embryo
Examples: Casein, the protein of milk, is the major source of amino
acids for baby mammals. Plants have storage proteins in their seeds.
Ovalbumin is the protein of egg white, used as an amino acid source
for the developing embryo.
Example: Insulin, a hormone secreted by the pancreas, causes other
tissues to take up glucose, thus regulating blood sugar
concentration.
Function: Coordination of an organism’s activities
Normal
blood sugar
High
blood sugar
Insulin
secreted
Examples: Motor proteins are responsible for the undulations of cilia
and flagella. Actin and myosin proteins are responsible for the
contraction of muscles.
Function: Movement
Muscle tissue
Actin Myosin
30 mm
Connective tissue
60 mm
Collagen
Examples: Keratin is the protein of hair, horns, feathers, and other skin
appendages. Insects and spiders use silk fibers to make their cocoons
and webs, respectively. Collagen and elastin proteins provide a fibrous
framework in animal connective tissues.
Function: Support
Signaling molecules
Receptor
protein
Example: Receptors built into the membrane of a nerve cell detect
signaling molecules released by other nerve cells.
Function: Response of cell to chemical stimuli
Examples: Hemoglobin, the iron-containing protein of vertebrate
blood, transports oxygen from the lungs to other parts of the body.
Other proteins transport molecules across cell membranes.
Function: Transport of substances
Transport
protein
Cell membrane
Antibodies
Bacterium
Virus
Function: Protection against disease
Example: Antibodies inactivate and help destroy viruses and bacteria.

95. © 2014 Pearson Education, Inc.
Figure 3.16a
Enzymatic proteins
Storage proteins
Defensive proteins
Transport proteins
Enzyme
Function: Selective acceleration of
chemical reactions
Function: Storage of amino acids
Example: Digestive enzymes catalyze the
hydrolysis of bonds in food molecules.
Ovalbumin Amino acids
for embryo
Examples: Casein, the protein of milk, is
the major source of amino acids for baby
mammals. Plants have storage proteins
in their seeds. Ovalbumin is the protein
of egg white, used as an amino acid
source for the developing embryo.
Examples: Hemoglobin, the iron-containing
protein of vertebrate blood, transports
oxygen from the lungs to other parts of the
body. Other proteins transport molecules
across cell membranes.
Function: Transport of substances
Transport
protein
Cell membrane
Antibodies
Bacterium
Virus
Function: Protection against disease
Example: Antibodies inactivate and help
destroy viruses and bacteria.

96. © 2014 Pearson Education, Inc.
Figure 3.16aa
Enzymatic proteins
Enzyme
Function: Selective acceleration of
chemical reactions
Example: Digestive enzymes catalyze the
hydrolysis of bonds in food molecules.

97. © 2014 Pearson Education, Inc.
Figure 3.16ab
Defensive proteins
Antibodies
Bacterium
Virus
Function: Protection against disease
Example: Antibodies inactivate and help
destroy viruses and bacteria.

98. © 2014 Pearson Education, Inc.
Figure 3.16ac
Storage proteins
Function: Storage of amino acids
Ovalbumin Amino acids
for embryo
Examples: Casein, the protein of milk, is
the major source of amino acids for baby
mammals. Plants have storage proteins
in their seeds. Ovalbumin is the protein
of egg white, used as an amino acid
source for the developing embryo.

99. © 2014 Pearson Education, Inc.
Figure 3.16aca

100. © 2014 Pearson Education, Inc.
Figure 3.16ad
Transport proteins
Examples: Hemoglobin, the iron-containing
protein of vertebrate blood, transports
oxygen from the lungs to other parts of the
body. Other proteins transport molecules
across cell membranes.
Function: Transport of substances
Transport
protein
Cell membrane

101. © 2014 Pearson Education, Inc.
Figure 3.16b
Hormonal proteins
Contractile and motor proteins
Receptor proteins
Structural proteins
Example: Insulin, a hormone secreted by
the pancreas, causes other tissues to
take up glucose, thus regulating blood
sugar concentration.
Function: Coordination of an organism’s
activities
Normal
blood sugar
High
blood sugar
Insulin
secreted
Examples: Motor proteins are responsible
for the undulations of cilia and flagella.
Actin and myosin proteins are
responsible for the contraction of
muscles.
Function: Movement
Muscle tissue
Actin Myosin
30 mm Connective tissue
60 mm
Collagen
Examples: Keratin is the protein of hair,
horns, feathers, and other skin appendages.
Insects and spiders use silk fibers to make
their cocoons and webs, respectively.
Collagen and elastin proteins provide a
fibrous framework in animal connective
tissues.
Function: Support
Signaling molecules
Receptor
protein
Example: Receptors built into the
membrane of a nerve cell detect signaling
molecules released by other nerve cells.
Function: Response of cell to chemical
stimuli

102. © 2014 Pearson Education, Inc.
Figure 3.16ba
Hormonal proteins
Example: Insulin, a hormone secreted by
the pancreas, causes other tissues to
take up glucose, thus regulating blood
sugar concentration.
Function: Coordination of an organism’s
activities
Normal
blood sugar
High
blood sugar
Insulin
secreted

103. © 2014 Pearson Education, Inc.
Figure 3.16bb
Receptor proteins
Signaling molecules
Receptor
protein
Example: Receptors built into the
membrane of a nerve cell detect signaling
molecules released by other nerve cells.
Function: Response of cell to chemical
stimuli

104. © 2014 Pearson Education, Inc.
Figure 3.16bc
Contractile and motor proteins
Examples: Motor proteins are responsible
for the undulations of cilia and flagella.
Actin and myosin proteins are
responsible for the contraction of
muscles.
Function: Movement
Muscle tissue
Actin Myosin
30 mm

105. © 2014 Pearson Education, Inc.
Figure 3.16bca
Muscle tissue
30 mm

106. © 2014 Pearson Education, Inc.
Figure 3.16bd
Structural proteins
Connective tissue
60 mm
Collagen
Examples: Keratin is the protein of hair,
horns, feathers, and other skin appendages.
Insects and spiders use silk fibers to make
their cocoons and webs, respectively.
Collagen and elastin proteins provide a
fibrous framework in animal connective
tissues.
Function: Support

107. © 2014 Pearson Education, Inc.
Figure 3.16bda
Connective tissue
60 mm

108. Life would not be possible without enzymes
Enzymatic proteins act as catalysts, to speed up
chemical reactions without being consumed by the
reaction
© 2014 Pearson Education, Inc.

109. Polypeptides are unbranched polymers built from
the same set of 20 amino acids
A protein is a biologically functional molecule that
consists of one or more polypeptides
© 2014 Pearson Education, Inc.

110. Amino Acids
Amino acids are organic molecules with carboxyl
and amino groups
Amino acids differ in their properties due to differing
side chains, called R groups
© 2014 Pearson Education, Inc.

111. © 2014 Pearson Education, Inc.
Figure 3.UN04
Side chain (R group)
Carboxyl
group
Amino
group
a carbon

112. © 2014 Pearson Education, Inc.
Figure 3.17
Nonpolar side chains; hydrophobic
Side chain
(R group)
Glycine
(Gly or G)
Alanine
(Ala or A)
Methionine
(Met or M)
Phenylalanine
(Phe or F)
Polar side chains; hydrophilic
Leucine
(Leu or L)
Isoleucine
(Ile or I)
Tryptophan
(Trp or W)
Proline
(Pro or P)
Valine
(Val or V)
Serine
(Ser or S)
Threonine
(Thr or T)
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Cysteine
(Cys or C)
Glutamine
(Gln or Q)
Aspartic acid
(Asp or D)
Glutamic acid
(Glu or E)
Arginine
(Arg or R)
Lysine
(Lys or K)
Histidine
(His or H)
Electrically charged side chains; hydrophilic
Acidic (negatively charged)
Basic (positively charged)

113. © 2014 Pearson Education, Inc.
Figure 3.17a
Nonpolar side chains; hydrophobic
Side chain
(R group)
Glycine
(Gly or G)
Alanine
(Ala or A)
Methionine
(Met or M)
Phenylalanine
(Phe or F)
Leucine
(Leu or L)
Isoleucine
(Ile or I)
Tryptophan
(Trp or W)
Proline
(Pro or P)
Valine
(Val or V)

114. © 2014 Pearson Education, Inc.
Figure 3.17b
Polar side chains; hydrophilic
Serine
(Ser or S)
Threonine
(Thr or T)
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Cysteine
(Cys or C)
Glutamine
(Gln or Q)

115. © 2014 Pearson Education, Inc.
Figure 3.17c
Aspartic acid
(Asp or D)
Glutamic acid
(Glu or E)
Arginine
(Arg or R)
Lysine
(Lys or K)
Histidine
(His or H)
Electrically charged side chains; hydrophilic
Acidic (negatively charged)
Basic (positively charged)

116. Polypeptides
Amino acids are linked by peptide bonds
A polypeptide is a polymer of amino acids
Polypeptides range in length from a few to more
than a thousand monomers
Each polypeptide has a unique linear sequence of
amino acids, with a carboxyl end (C-terminus) and
an amino end (N-terminus)
© 2014 Pearson Education, Inc.

117. © 2014 Pearson Education, Inc.
Figure 3.18
New peptide
bond forming
Peptide bond
Side
chains
Back-
bone
Amino end
(N-terminus)
Carboxyl end
(C-terminus)
Peptide
bond

118. © 2014 Pearson Education, Inc.
Figure 3.18a
Peptide bond

119. © 2014 Pearson Education, Inc.
Figure 3.18b
Side
chains
Back-
bone
Amino end
(N-terminus)
Carboxyl end
(C-terminus)
Peptide
bond

120. Protein Structure and Function
A functional protein consists of one or more
polypeptides precisely twisted, folded, and coiled
into a unique shape
© 2014 Pearson Education, Inc.

121. © 2014 Pearson Education, Inc.
Figure 3.19
(a) A ribbon model (b) A space-filling model
Groove
Groove

122. © 2014 Pearson Education, Inc.
Figure 3.19a
(a) A ribbon model
Groove

123. © 2014 Pearson Education, Inc.
Figure 3.19b
(b) A space-filling model
Groove

124. The sequence of amino acids, determined
genetically, leads to a protein’s three-dimensional
structure
A protein’s structure determines its function
© 2014 Pearson Education, Inc.

125. © 2014 Pearson Education, Inc.
Figure 3.20
Antibody proteinProtein from flu virus

126. Four Levels of Protein Structure
Proteins are very diverse, but share three
superimposed levels of structure called primary,
secondary, and tertiary structure
A fourth level, quaternary structure, arises when a
protein consists of more than one polypeptide chain
© 2014 Pearson Education, Inc.

127. The primary structure of a protein is its unique
sequence of amino acids
Secondary structure, found in most proteins,
consists of coils and folds in the polypeptide chain
Tertiary structure is determined by interactions
among various side chains (R groups)
Quaternary structure results from interactions
between multiple polypeptide chains
© 2014 Pearson Education, Inc.

128. © 2014 Pearson Education, Inc.
Video: Alpha Helix with No Side Chain
Video: Alpha Helix with Side Chain
Video: Beta Pleated Sheet
Video: Beta Pleated Stick
Animation: Introduction to Protein Structure
Animation: Primary Structure
Animation: Secondary Structure
Animation: Tertiary Structure
Animation: Quaternary Structure

129. © 2014 Pearson Education, Inc.
Figure 3.21a
Primary structure
Amino end
Carboxyl end
Primary structure of transthyretin
125
95
90
100105110
120
115
80
70 60
85
75
65
55
504540
2530
35
20 15
10
51
Amino
acids

130. © 2014 Pearson Education, Inc.
Figure 3.21aa
Primary structure
Amino end
2530 20 15
10
5
1
Amino
acids

131. © 2014 Pearson Education, Inc.
Figure 3.21b
Secondary
structure
Tertiary
structure
Quaternary
structure
Transthyretin
polypeptide
Transthyretin
protein
b pleated sheet
a helix

132. © 2014 Pearson Education, Inc.
Figure 3.21ba
Secondary structure
Hydrogen
bond
b pleated sheet
a helix
Hydrogen bond
b strand

133. © 2014 Pearson Education, Inc.
Figure 3.21bb
Tertiary structure
Transthyretin
polypeptide

134. © 2014 Pearson Education, Inc.
Figure 3.21bc
Quaternary structure
Transthyretin
protein

135. © 2014 Pearson Education, Inc.
Figure 3.21c

136. © 2014 Pearson Education, Inc.
Figure 3.21d
Hydrogen
bond
Disulfide
bridge
Polypeptide
backbone
Hydrophobic
interactions and
van der Waals
interactions
Ionic bond

137. © 2014 Pearson Education, Inc.
Figure 3.21e
Collagen

138. © 2014 Pearson Education, Inc.
Figure 3.21f
Heme
Iron
a subunit
a subunit
b subunit
b subunit
Hemoglobin

139. Sickle-Cell Disease: A Change in Primary Structure
Primary structure is the sequence of amino acids
on the polypeptide chain
A slight change in primary structure can affect a
protein’s structure and ability to function
Sickle-cell disease, an inherited blood disorder,
results from a single amino acid substitution in the
protein hemoglobin
© 2014 Pearson Education, Inc.

140. © 2014 Pearson Education, Inc.
Figure 3.22
b subunit
b subunit
Function
Red Blood Cell
Shape
Quaternary
Structure
Secondary
and Tertiary
Structures
Primary
Structure
Normal
hemoglobin
Sickle-cell
hemoglobin
Exposed hydro-
phobic region
Molecules crystallized
into a fiber; capacity to
carry oxygen is reduced.
Molecules do not
associate with one
another; each carries
oxygen.
b
b
b
b
a
a
a
a
1
2
3
4
5
6
7
1
2
3
4
5
6
7
N
o
r
m
a
l
S
i
c
k
l
e
-
c
e
l
l
5 mm
5 mm

141. © 2014 Pearson Education, Inc.
Figure 3.22a
b subunit
Function
Quaternary
Structure
Secondary
and Tertiary
Structures
Primary
Structure
Normal
hemoglobin
Molecules do not
associate with one
another; each carries
oxygen.
b
b
a
a
1
2
3
4
5
6
7
N
o
r
m
a
l

142. © 2014 Pearson Education, Inc.
Figure 3.22aa
5 mm

143. © 2014 Pearson Education, Inc.
Figure 3.22b
b subunit
Function
Quaternary
Structure
Secondary
and Tertiary
Structures
Primary
Structure
Sickle-cell
hemoglobin
Exposed hydro-
phobic region
Molecules crystallized
into a fiber; capacity to
carry oxygen is reduced.
b
b
a
a
1
2
3
4
5
6
7S
i
c
k
l
e
-
c
e
l
l

144. © 2014 Pearson Education, Inc.
Figure 3.22ba
5 mm

145. What Determines Protein Structure?
In addition to primary structure, physical and
chemical conditions can affect structure
Alterations in pH, salt concentration, temperature, or
other environmental factors can cause a protein to
unravel
This loss of a protein’s native structure is called
denaturation
A denatured protein is biologically inactive
© 2014 Pearson Education, Inc.

146. © 2014 Pearson Education, Inc.
Figure 3.23-1
Normal protein

147. © 2014 Pearson Education, Inc.
Figure 3.23-2
Normal protein Denatured protein

148. © 2014 Pearson Education, Inc.
Figure 3.23-3
Denatured proteinNormal protein

149. Protein Folding in the Cell
It is hard to predict a protein’s structure from its
primary structure
Most proteins probably go through several
intermediate structures on their way to their final,
stable shape
Scientists use X-ray crystallography to determine
3-D protein structure based on diffractions of an
X-ray beam by atoms of the crystalized molecule
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150. © 2014 Pearson Education, Inc.
Figure 3.24
Digital detectorCrystal
Experiment
Results
X-ray
source
X-ray
beam
X-ray diffraction
pattern
Diffracted
X-rays
DNARNA
RNA
polymerase II

151. © 2014 Pearson Education, Inc.
Figure 3.24a
Digital detectorCrystal
Experiment
X-ray
source
X-ray
beam
X-ray diffraction
pattern
Diffracted
X-rays

152. © 2014 Pearson Education, Inc.
Figure 3.24b
Results
DNARNA
RNA
polymerase II

153. Concept 3.6: Nucleic acids store, transmit, and
help express hereditary information
The amino acid sequence of a polypeptide is
programmed by a unit of inheritance called a gene
Genes are made of DNA, a nucleic acid made of
monomers called nucleotides
© 2014 Pearson Education, Inc.

154. The Roles of Nucleic Acids
There are two types of nucleic acids
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
DNA provides directions for its own replication
DNA directs synthesis of messenger RNA (mRNA)
and, through mRNA, controls protein synthesis
© 2014 Pearson Education, Inc.

155. © 2014 Pearson Education, Inc.
Figure 3.25-1
CYTOPLASM
NUCLEUS
Synthesis
of mRNA
mRNA
DNA
1

156. © 2014 Pearson Education, Inc.
Figure 3.25-2
CYTOPLASM
mRNA
Movement of
mRNA into
cytoplasm
NUCLEUS
Synthesis
of mRNA
mRNA
DNA
2
1

157. © 2014 Pearson Education, Inc.
Figure 3.25-3
CYTOPLASM
Ribosome
Amino
acids
mRNA
Polypeptide
Synthesis
of protein
Movement of
mRNA into
cytoplasm
NUCLEUS
Synthesis
of mRNA
mRNA
DNA
3
2
1

158. The Components of Nucleic Acids
Nucleic acids are polymers called polynucleotides
Each polynucleotide is made of monomers called
nucleotides
Each nucleotide consists of a nitrogenous base, a
pentose sugar, and one or more phosphate groups
The portion of a nucleotide without the phosphate
group is called a nucleoside
© 2014 Pearson Education, Inc.
Animation: DNA and RNA Structure

159. © 2014 Pearson Education, Inc.
Figure 3.26
Sugar-phosphate backbone
(on blue background)
(a) Polynucleotide, or nucleic acid
(b) Nucleotide
(c) Nucleoside components
5¢ end
3¢ end
5¢C
5¢C
3¢C
3¢C
Phosphate
group
Sugar
(pentose)
Nitrogenous
base
Nucleoside
Nitrogenous bases
Pyrimidines
Cytosine (C) Thymine
(T, in DNA)
Uracil
(U, in RNA)
Purines
Adenine (A) Guanine (G)
Sugars
Deoxyribose (in DNA) Ribose (in RNA)

160. © 2014 Pearson Education, Inc.
Figure 3.26a
Sugar-phosphate backbone
(on blue background)
(a) Polynucleotide, or nucleic acid
(b) Nucleotide
5¢ end
3¢ end
5¢C
5¢C
3¢C
3¢C
Phosphate
group
Sugar
(pentose)
Nitrogenous
base
Nucleoside

161. © 2014 Pearson Education, Inc.
Figure 3.26b
(b) Nucleotide
Phosphate
group
Sugar
(pentose)
Nitrogenous
base
Nucleoside

162. © 2014 Pearson Education, Inc.
Figure 3.26c
Nitrogenous bases
Pyrimidines
Cytosine (C) Thymine
(T, in DNA)
Uracil
(U, in RNA)
Purines
Adenine (A) Guanine (G)

163. © 2014 Pearson Education, Inc.
Figure 3.26d
Sugars
Deoxyribose (in DNA) Ribose (in RNA)

164. Each nitrogenous base has one or two rings that
include nitrogen atoms
The nitrogenous bases in nucleic acids are called
cytosine (C), thymine (T), uracil (U), adenine (A),
and guanine (G)
Thymine is found only in DNA, and uracil only in
RNA; the rest are found in both DNA and RNA
© 2014 Pearson Education, Inc.

165. The sugar in DNA is deoxyribose; in RNA it is
ribose
A prime (¢) is used to identify the carbon atoms in the
ribose, such as the 2¢ carbon or 5¢ carbon
A nucleoside with at least one phosphate attached is
a nucleotide
© 2014 Pearson Education, Inc.

166. Nucleotide Polymers
Adjacent nucleotides are joined by covalent bonds
that form between the —OH group on the 3¢ carbon
of one nucleotide and the phosphate on the 5¢
carbon of the next
These links create a backbone of sugar-phosphate
units with nitrogenous bases as appendages
The sequence of bases along a DNA or mRNA
polymer is unique for each gene
© 2014 Pearson Education, Inc.

167. The Structures of DNA and RNA Molecules
RNA molecules usually exist as single polypeptide
chains
DNA molecules have two polynucleotides spiraling
around an imaginary axis, forming a double helix
In the DNA double helix, the two backbones run in
opposite 5¢→ 3¢ directions from each other, an
arrangement referred to as antiparallel
One DNA molecule includes many genes
© 2014 Pearson Education, Inc.

168. The nitrogenous bases in DNA pair up and form
hydrogen bonds: adenine (A) always with thymine
(T), and guanine (G) always with cytosine (C)
This is called complementary base pairing
Complementary pairing can also occur between
two RNA molecules or between parts of the same
molecule
In RNA, thymine is replaced by uracil (U), so A and
U pair
© 2014 Pearson Education, Inc.

169. © 2014 Pearson Education, Inc.
Animation: DNA Double Helix
Video: DNA Stick Model
Video: DNA Surface Model

170. © 2014 Pearson Education, Inc.
Figure 3.27
(a) DNA
Sugar-phosphate
backbones
5¢
5¢
3¢
3¢
(b) Transfer RNA
Base pair joined
by hydrogen bonding
Hydrogen bonds
Base pair joined
by hydrogen
bonding

171. © 2014 Pearson Education, Inc.
Figure 3.27a
(a) DNA
Sugar-phosphate
backbones
5¢
5¢
3¢
3¢
Base pair joined
by hydrogen bonding
Hydrogen bonds

172. © 2014 Pearson Education, Inc.
Figure 3.27b
Sugar-phosphate
backbones
(b) Transfer RNA
Hydrogen bonds
Base pair joined
by hydrogen
bonding

173. DNA and Proteins as Tape Measures of Evolution
The linear sequences of nucleotides in DNA
molecules are passed from parents to offspring
Two closely related species are more similar in DNA
than are more distantly related species
Molecular biology can be used to assess
evolutionary kinship
© 2014 Pearson Education, Inc.

174. © 2014 Pearson Education, Inc.
Figure 3.UN05

175. © 2014 Pearson Education, Inc.
Figure 3.UN06

176. © 2014 Pearson Education, Inc.
Figure 3.UN06a

177. © 2014 Pearson Education, Inc.
Figure 3.UN06b

178. © 2014 Pearson Education, Inc.
Figure 3.UN07