Download Biomolecules PowerPoint Notes

Chapter 5
The Structure and Function of
Macromolecules
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Overview: The Molecules of Life
– Another level in the hierarchy of biological
organization is reached when small organic
molecules are joined together
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• Macromolecules
– Are large molecules composed of smaller
molecules
– Are complex in their structures
Figure 5.1
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Concept 5.1: Most macromolecules are
polymers, built from monomers
• Three of the classes of life’s organic
molecules are polymers
– Carbohydrates
– Proteins
– Nucleic acids
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• A polymer
– Is a long molecule consisting of many similar
building blocks called monomers
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The Synthesis and Breakdown of Polymers
• Monomers form larger molecules by
condensation reactions called dehydration
reactions
HO
1
3
2
H
Unlinked monomer
Short polymer
Dehydration removes a water
molecule, forming a new bond
HO
Figure 5.2A
1
2
H
HO
3
H2O
4
H
Longer polymer
(a) Dehydration reaction in the synthesis of a polymer
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• Polymers can disassemble by
– Hydrolysis
HO
1
2
3
4
Hydrolysis adds a water
molecule, breaking a bond
HO
1
2
3
H
Figure 5.2B (b) Hydrolysis of a polymer
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H
H2O
HO
H
The Diversity of Polymers
• Each class of polymer
– Is formed from a specific set of monomers
1
2
3
H
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HO
• Although organisms share the same limited
number of monomer types, each organism is
unique based on the arrangement of
monomers into polymers
• An immense variety of polymers can be built
from a small set of monomers
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• Concept 5.2: Carbohydrates serve as fuel and
building material
• Carbohydrates
– Include both sugars and their polymers
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Sugars
• Monosaccharides
– Are the simplest sugars
– Can be used for fuel
– Can be converted into other organic molecules
– Can be combined into polymers
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• Examples of monosaccharides
Triose sugars Pentose sugars
(C3H6O3)
(C5H10O5)
H
O
H
Aldoses
C
O
H
C
H
O
C
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
HO
C
H
C
OH
H
H
C
OH
H
H
Ribose
H
H
C
H
C
OH
H
HO
C
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
H
Glucose
Galactose
H
C OH
H
C
O
H
C OH
H
C OH
C
O
O
C OH
H
C OH
HO
H
H
C OH
H
C OH
Dihydroxyacetone
H
C OH
H
C OH
H
H
C OH
H
Ribulose
Figure 5.3
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O
C
H
Glyceraldehyde
Ketoses
Hexose sugars
(C6H12O6)
C H
H
Fructose
• Monosaccharides
– May be linear
– Can form rings
O
H
1C
H
HO
2
3
C
6CH OH
2
OH
H
C
H
4
H
H
H
C
5
5C
6
C
H
OH
4C
OH
OH
OH
O
5C
H
H
OH
C
6CH OH
2
3
C
H
2C
O
H
H
4C
1C
CH2OH
O
OH
H
OH
3C
6
H
1C
H
2C
4
HO
H
OH
3
OH
H
1
2
OH
OH
OH
H
Figure 5.4 (a) Linear and ring forms. Chemical equilibrium between the linear and ring
structures greatly favors the formation of rings. To form the glucose ring,
carbon 1 bonds to the oxygen attached to carbon 5.
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H
OH
H
H
O
5
• Disaccharides
– Consist of two monosaccharides
– Are joined by a glycosidic linkage
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• Examples of disaccharides
(a) Dehydration reaction
in the synthesis of
maltose. The bonding
of two glucose units
forms maltose. The
glycosidic link joins
the number 1 carbon
of one glucose to the
number 4 carbon of
the second glucose.
Joining the glucose
monomers in a
different way would
result in a different
disaccharide.
CH2OH
CH2OH
H
O
H
OH H
OH
HO
H
H
H
HO
O
H
OH
H
OH
H
CH2OH
H
OHOH
H
O
H
OH H
CH2OH
H
1–4
1 glycosidic
linkage
HO
4
O
H
H
OH H
OH
O
H
OH
H
H
OH
OH
H2O
Glucose
Glucose
CH2OH
H
(b) Dehydration reaction
in the synthesis of
HO
sucrose. Sucrose is
a disaccharide formed
from glucose and fructose.
Notice that fructose,
though a hexose like
glucose, forms a
five-sided ring.
O
H
OH
H
H
CH2OH
H
OH
HO
CH2OH
O
H
H
H
HO
CH2OH
OH
OH
Maltose
H
O
H
OH
H
1–2
glycosidic
1
linkage
H
Fructose
Figure 5.5
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2
H
H
CH2OH
OH H
OH
Sucrose
H
HO
O
HO
H2O
Glucose
CH2OH
O
Polysaccharides
• Polysaccharides
– Are polymers of sugars
– Serve many roles in organisms
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Storage Polysaccharides
• Starch
– Is a polymer consisting entirely of glucose
monomers
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– Is the major storage form of glucose in plants
Chloroplast
Starch
1 m
Amylose
Amylopectin
Figure 5.6 (a) Starch: a plant polysaccharide
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• Glycogen
– Consists of glucose monomers
– Is the major storage form of glucose in animals
Mitochondria
Giycogen
granules
0.5 m
Glycogen
Figure 5.6 (b) Glycogen: an animal polysaccharide
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Structural Polysaccharides
• Cellulose
– Is a polymer of glucose
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– Has different glycosidic linkages than starch
H
CH2O
H
O
H
OH H
H
4
H
OH
HO
H
O
CH2O
H
H
O OH
H
4
1
OH H
HO
H
C
OH
 glucose
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
OH
 glucose
(a)  and  glucose ring structures
CH2O
H
O
CH2O
H
O
HO
4
1
OH
O
1
OH
4
O
1
OH
OH
OH
CH2O
H
O
CH2O
H
O
O
4
1
OH
O
OH
OH
(b) Starch: 1– 4 linkage of  glucose monomers
CH2O
H
O
HO
Figure 5.7 A–C
OH
CH2O
H
O
OH
O
1
4
OH
O
OH
OH
O
OH
O
O
CH2O
CH2O
OH
OH
H
H
(c) Cellulose: 1– 4 linkage of  glucose monomers
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OH
– Is a major component of the tough walls that
enclose plant cells
Cell walls
Cellulose microfibrils
in a plant cell wall
Microfibril
About 80 cellulose
molecules associate
to form a microfibril, the
main architectural unit
of the plant cell wall.
0.5 m
Plant cells
Parallel cellulose molecules are
held together by hydrogen
bonds between hydroxyl
groups attached to carbon
atoms 3 and 6.
Figure 5.8
OH CH2OH
OH
CH2OH
O O
O O
OH
OH
OH
OH
O
O O
O O
O CH OH
OH
CH2OH
2
H
CH2OH
OH CH2OH
OH
O O
O O
OH
OH
OH
OH
O
O O
O O
O CH OH
OH CH2OH
2
H
CH2OH
OH
OH CH2OH
O O
O O
OH
OH
OH O
O OH
O O
O
O CH OH
OH CH2OH
2
H
 Glucose
monomer
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Cellulose
molecules
A cellulose molecule
is an unbranched 
glucose polymer.
• Cellulose is difficult to digest
– Cows have microbes in their stomachs to
facilitate this process
Figure 5.9
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• Chitin, another important structural
polysaccharide
– Is found in the exoskeleton of arthropods
– Can be used as surgical thread
CH2O
H
O OH
H
H
OH H
OH
H
H
NH
C
O
CH3
(a) The structure of the (b) Chitin forms the exoskeleton
of arthropods. This cicada
chitin monomer.
is molting, shedding its old
exoskeleton and emerging
Figure 5.10 A–C
in adult form.
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(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.
• Concept 5.3: Lipids are a diverse group of
hydrophobic molecules
• Lipids
– Are the one class of large biological molecules
that do not consist of polymers
– Share the common trait of being hydrophobic
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Fats
• Fats
– Are constructed from two types of smaller
molecules, a single glycerol and usually three
fatty acids
H
H
C
O
C
OH
HO
H
C
OH
H
C
OH
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
Fatty acid
(palmitic acid)
H
Glycerol
(a) Dehydration reaction in the synthesis of a fat
Ester linkage
O
H
H
C
O
C
H
C
H
O
H
C
O
C
O
H
C
H
Figure 5.11
O
C
H
C
H
H
C
H
C
H
H
H
C
H
C
H
H
H
C
H
H
C
H
H
C
H
H
C
H
C
H
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
(b) Fat molecule (triacylglycerol)
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H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
C
H
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
H
C
H
H
H
C
H
H
• Fatty acids
– Vary in the length and number and locations of
double bonds they contain
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• Saturated fatty acids
– Have the maximum number of hydrogen atoms
possible
– Have no double bonds
Stearic acid
Figure 5.12 (a) Saturated fat and fatty acid
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• Unsaturated fatty acids
– Have one or more double bonds
Oleic acid
Figure 5.12
(b) Unsaturated fat and fatty acid
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cis double bond
causes bending
Phospholipids
• Phospholipids
– Have only two fatty acids
– Have a phosphate group instead of a third
fatty acid
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• Phospholipid structure
– Consists of a hydrophilic “head” and
hydrophobic “tails”
CH2
+
N(CH )
Choline
3 3
CH2
O
O
P
O–
Phosphate
O
CH2
CH
O
O
C
O C
CH2
Glycerol
O
Fatty acids
Hydrophilic
head
Hydrophobic
tails
Figure 5.13
(a) Structural formula
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(b) Space-filling model
(c) Phospholipid
symbol
• The structure of phospholipids
– Results in a bilayer arrangement found in cell
membranes
WATER
Hydrophilic
head
WATER
Hydrophobic
tail
Figure 5.14
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Steroids
• Steroids
– Are lipids characterized by a carbon skeleton
consisting of four fused rings
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• One steroid, cholesterol
– Is found in cell membranes
– Is a precursor for some hormones
H3C
CH3
CH3
Figure 5.15
HO
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CH3
CH3
• Concept 5.4: Proteins have many structures,
resulting in a wide range of functions
– Proteins
• Have many roles inside the cell
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• An overview of protein functions
Table 5.1
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• Enzymes
– Are a type of protein that acts as a catalyst,
speeding up chemical reactions
1 Active site is available for
a molecule of substrate, the
reactant on which the enzyme acts.
Substrate
(sucrose)
2 Substrate binds to
enzyme.
Glucose
OH
Enzyme
(sucrase)
H2O
Fructose
H O
4 Products are released.
Figure 5.16
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3 Substrate is converted
to products.
Polypeptides
• Polypeptides
– Are polymers of amino acids
• A protein
– Consists of one or more polypeptides
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Amino Acid Monomers
• Amino acids
– Are organic molecules possessing both
carboxyl and amino groups
– Differ in their properties due to differing side
chains, called R groups
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• 20 different amino acids make up proteins
CH3
CH3
H
H3N+
C
CH3
O
H3N+
C
H
Glycine (Gly)
O–
C
H3N+
C
H
Alanine (Ala)
O–
CH
CH3
CH3
O
C
CH2
CH2
O
H3N+
C
H
Valine (Val)
CH3
CH3
O–
C
O
H3N+
C
H
Leucine (Leu)
H3C
O–
CH
C
O
C
O–
H
Isoleucine (Ile)
Nonpolar
CH3
CH2
S
NH
CH2
CH2
H3N+
C
H
CH2
O
H3N+
C
O–
Methionine (Met)
C
H
H3 N+
C
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C
O–
Phenylalanine (Phe)
Figure 5.17
CH2
O
H
O
H2C
CH2
H2N
C
O
C
O–
H
C
O–
Tryptophan (Trp)
Proline (Pro)
OH
OH
Polar
CH2
H3N+
C
CH
O
H3N+
C
O–
H
Serine (Ser)
C
CH2
O
H3N+
C
O–
H
C
CH2
O
C
H
O–
H3N+
C
O
H3N+
C
O–
H
Electrically
charged
H3N+
CH2
C
H3N+
O–
C
NH3+
O
C
CH2
C
CH2
CH2
CH2
CH2
CH2
CH2
O
CH2
C
O–
H
H3N+
C
O
CH2
C
H
O–
H3N+
C
H
O–
H
Glutamic acid
(Glu)
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NH+
C
O–
Lysine (Lys)
NH2+
H3N+
CH2
O
CH2
H3N+
C
H
Aspartic acid
(Asp)
O
C
Glutamine
(Gln)
NH2
C
C
C
Basic
O–
O
O
Asparagine
(Asn)
Acidic
–O
CH2
CH2
H
Tyrosine
(Tyr)
Cysteine
(Cys)
Threonine (Thr)
C
NH2 O
C
SH
CH3
OH
NH2 O
NH
CH2
O
C
C
O–
H
O
C
O–
Arginine (Arg)
Histidine (His)
Amino Acid Polymers
• Amino acids
– Are linked by peptide bonds
Peptide
bond
OH
CH2
SH
CH2
H
N
H
OH
CH2
H
C C
H
N C C OH H N C
H O
H O
H
(a)
C OH
O DESMOSOMES
H2O
OH
DESMOSOMES
DESMOSOMES
SH
OH
Peptide
CH2 bond CH2
CH2
H
H N C C
H O
Figure 5.18
(b)
Amino end
(N-terminus)
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H
H
N C C
H O
N C C OH
H O
Carboxyl end
(C-terminus)
Side
chains
Backbone
Determining the Amino Acid Sequence of a Polypeptide
• The amino acid sequences of polypeptides
– Were first determined using chemical means
– Can now be determined by automated
machines
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Protein Conformation and Function
• A protein’s specific conformation
– Determines how it functions
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• Two models of protein conformation
Groove
(a) A ribbon model
Groove
Figure 5.19
(b) A space-filling model
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Four Levels of Protein Structure
• Primary structure
– Is the unique sequence of amino acids in a
polypeptide
HN
Amino acid
+
Gly ProThr Gly
Thr
3
Amino
end
Gly
Glu
Cys LysSeu
LeuPro
Met
Val
Lys
subunits
Val
Leu
Asp
AlaVal Arg Gly
Ser
Pro
Ala
Glu Lle
Leu Ala
Gly
Asp
Thr
Lys
Ser
Lys Trp Tyr
lle
Ser
ProPhe
His Glu
Ala Thr PheVal
Asn
His
Ala
Glu
Val
Asp
Tyr
Arg
Ser
Arg
Gly Pro
Thr Ser
Tyr
Thr
lle
Ala
Ala
Leu
Leu
Ser
Pro
SerTyr
Thr
Ala
Val
Val
LysGlu
Thr
AsnPro
Figure 5.20
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c
o
o–
Carboxyl end
• Secondary structure
– Is the folding or coiling of the polypeptide into a
repeating configuration
– Includes the  helix and the  pleated sheet
 pleated sheet
O H H
C C N
Amino acid
subunits
C N
H
R
R
O H H
C C N
C C N
O H H
R
R
O H H
C C N
C C N
OH H
R
R
R
O
R
C
H
H
R
O C
O C
N H
N H
N H
O C
O C
H C R H C R
H C R H C
R
N H O C
N H
O C
O C
H
C
O
N H
N
C
C
H
R
H
R
N
C
C
H
H
 helix
Figure 5.20
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O H H
C C N
C C N
OH H
R
O
C
H
H
H C N HC
C N HC N
C
N
H
H
C
O
C
C
O
R
R
O
R
O
C
H
H
NH C N
C
H
O C
R
C C
O
R
R
H
C
N HC N
H
O C
• Tertiary structure
– Is the overall three-dimensional shape of a
polypeptide
– Results from interactions between amino acids
and R groups
Hydrophobic
Hyrdogen
bond
CH22
CH
O
H
O
CH
H3C
CH3
H3C
CH3
CH
interactions and
van der Waals
interactions
Polypeptide
backbone
HO C
CH2
CH2 S S CH2
Disulfide bridge
O
CH2 NH3+ -O C CH2
Ionic bond
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• Quaternary structure
– Is the overall protein structure that results from
the aggregation of two or more polypeptide
subunits
Polypeptide
chain
Collagen
 Chains
Iron
Heme
 Chains
Hemoglobin
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• The four levels of protein structure
+H
3N
Amino end
Amino acid
subunits
helix
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Sickle-Cell Disease: A Simple Change in
Primary Structure
• Sickle-cell disease
– Results from a single amino acid substitution in
the protein hemoglobin
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• Hemoglobin structure and sickle-cell disease
Primary
structure
Normal hemoglobin
Val
His Leu Thr
1 2 3 4 5 6 7
Secondary
and tertiary
structures
Red blood
cell shape
Val
His
Leu Thr


Molecules do
not associate
with one
another, each
carries oxygen.


Quaternary
structure
Figure 5.21
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Val Glu
...




10 m
Red blood
cell shape
Exposed
hydrophobic
region
 subunit
Function
10 m
Normal cells are
full of individual
hemoglobin
molecules, each
carrying oxygen
Pro
structure 1 2 3 4 5 6 7
Secondary
 subunit and tertiary
structures
Quaternary Hemoglobin A
structure
Function
Pro Glul Glu
Sickle-cell hemoglobin
. . . Primary
Hemoglobin S
Molecules
interact with
one another to
crystallize into a
fiber, capacity to
carry oxygen is
greatly reduced.
Fibers of abnormal
hemoglobin
deform cell into
sickle shape.
What Determines Protein Conformation?
• Protein conformation
– Depends on the physical and chemical
conditions of the protein’s environment
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1. What happens when a protein denatures? *
a. It loses its primary structure.
b. It loses its secondary and tertiary structure.
c. It becomes irreversibly insoluble and
precipitates.
d. It hydrolyzes into component amino acids.
e. Its hydrogen bonds, ionic bonds, and peptide
bonds are disrupted.
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• Denaturation
– Is when a protein unravels and loses its native
conformation
Denaturation
Normal protein
Figure 5.22
Denatured protein
Renaturation
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The Protein-Folding Problem
• Most proteins
– Probably go through several intermediate
states on their way to a stable conformation
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• Chaperonins
– Are protein molecules that assist in the proper
folding of other proteins
Polypeptide
Cap
Correctly
folded
protein
Hollow
cylinder
Chaperonin
(fully assembled)
Figure 5.23
Steps of Chaperonin
Action:
1 An unfolded polypeptide enters the
cylinder from one end.
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2 The cap attaches, causing
3 The cap comes
the cylinder to change shape in off, and the properly
such a way that it creates a
folded protein is
hydrophilic environment for the released.
folding of the polypeptide.
• X-ray crystallography
– Is used to determine a protein’s threeX-ray
dimensional structure
diffraction
pattern
Photographic film
Diffracted X-rays
X-ray
X-ray
beam
source
Crystal Nucleic acid Protein
Figure 5.24
(a) X-ray diffraction pattern
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(b) 3D computer model
• Concept 5.5: Nucleic acids store and transmit
hereditary information
• Genes
– Are the units of inheritance
– Program the amino acid sequence of
polypeptides
– Are made of nucleic acids
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The Roles of Nucleic Acids
• There are two types of nucleic acids
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
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• DNA
– Stores information for the synthesis of specific
proteins
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– Directs RNA synthesis
– Directs protein synthesis through RNA
DNA
1 Synthesis of
mRNA in the nucleus
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into cytoplasm
via nuclear pore
Ribosome
3 Synthesis
of protein
Figure 5.25
Polypeptide
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Amino
acids
The Structure of Nucleic Acids
• Nucleic acids
– Exist as polymers called polynucleotides
5’ end
5’C
O
3’C
O
O
5’C
O
3’C
OH
Figure 5.26
3’ end
(a) Polynucleotide,
or nucleic acid
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• Each polynucleotide
– Consists of monomers called nucleotides
Nucleoside
Nitrogenous
base
5’C
O

O
P
O
CH2
O
O
Phosphate
group
Figure 5.26
(b) Nucleotide
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3’C
Pentose
sugar
Nucleotide Monomers
• Nucleotide monomers
– Are made up of nucleosides and phosphate
groups
Nitrogenous bases
Pyrimidines
NH2
O
O
C
C
CH
C
3
N
CH
C
CH HN
HN
CH
C
CH
C
C
CH
N
N
O
N
O
O
H
H
H
Cytosine Thymine (in DNA) Uracil
(in
RNA)
Uracil (in RNA)
U
C
U
T
Purines
O
NH2
N C C
N CC
NH
N
HC
HC
C
CH
N C
N
NH2
N
N
H
H
Adenine
Guanine
A
G
5”
Pentose sugars
HOCH2 O OH
4’
H H
1’
5”
HOCH2 O OH
4’
H H
1’
H
H
H 3’ 2’ H
3’ 2’
OH H
OH OH
Deoxyribose (in DNA) Ribose (in RNA)
Figure 5.26
(c) Nucleoside components
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Nucleotide Polymers
• Nucleotide polymers
– Are made up of nucleotides linked by the–OH
group on the 3´ carbon of one nucleotide and
the phosphate on the 5´ carbon on the next
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• The sequence of bases along a nucleotide
polymer
– Is unique for each gene
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The DNA Double Helix
• Cellular DNA molecules
– Have two polynucleotides that spiral around an
imaginary axis
– Form a double helix
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• The DNA double helix
– Consists of two antiparallel nucleotide strands
5’ end
3’ end
Sugar-phosphate
backbone
Base pair (joined by
hydrogen bonding)
Old strands
A 3’ end
Nucleotide
about to be
added to a
new strand
5’ end
3’ end
Figure 5.27
5’ end
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New
strands
3’ end
• The nitrogenous bases in DNA
– Form hydrogen bonds in a complementary
fashion (A with T only, and C with G only)
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DNA and Proteins as Tape Measures of Evolution
• Molecular comparisons
– Help biologists sort out the evolutionary
connections among species
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The Theme of Emergent Properties in the
Chemistry of Life: A Review
• Higher levels of organization
– Result in the emergence of new properties
• Organization
– Is the key to the chemistry of life
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