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Chapter 3
The Molecules of Cells
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Got Lactose?
• Many people in the world suffer from lactose
intolerance
–
Lacking an enzyme that digests lactose, a
sugar found in milk
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Lactose intolerance illustrates the importance of
biological molecules
– To the functioning of living cells and to
human health
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
INTRODUCTION TO ORGANIC COMPOUNDS
3.1 Life’s molecular diversity is based on the
properties of carbon
• A carbon atom can form four covalent bonds
–
Allowing it to build large and diverse organic
compounds
Structural
formula
Ball-and-stick
model
H
H
C
Space-filling
model
H
H
H
C
H
Methane
H
H
The 4 single bonds of carbon point to the corners of a tetrahedron.
Figure 3.1A
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• Carbon chains vary in many ways
H
H
H
C
C
H
H
H
Ethane
H
H
H
H
C
C
C
H
H
H
H
Propane
Carbon skeletons vary in length.
H
C
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
H
H
H
H
C
C
C
H
H
H
H
Butane
Isobutane
Skeletons may be unbranched or branched.
H
H
H
H
H
C
C
C
C
H
H
H
H
H
H
C
C
C
C
H
H H
H
H
1-Butene
2-Butene
Skeletons may have double bonds, which can vary in location.
H
H
H
C
H
C
H C
H
C
C
H
C
H
H
H
H
H
H
H
C
C
C
H
C
C
C
H
Benzene
Cyclohexane
Skeletons may be arranged in rings.
Figure 3.1A
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H
H
• Hydrocarbons
–
Are composed of only hydrogen and carbon
• Some carbon compounds are isomers
–
Molecules with the same molecular formula
but different structures
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3.2 Functional groups help determine the properties
of organic compounds
• Examples of functional groups
Table 3.2
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• Functional groups are particular groupings of atoms
–
That give organic molecules particular
properties
OH
Estradiol
HO
Female lion
OH
O
Figure 3.2
Male lion
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Testosterone
3.3 Cells make a huge number of large
molecules from a small set of small molecules
• The four main classes of biological molecules
– Are carbohydrates, lipids, proteins, and
nucleic acids
• Many of the molecules are gigantic
– And are called macromolecules
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• Cells make most of their large molecules
–
By joining smaller organic molecules into
chains called polymers
• Cells link monomers to form polymers
–
By a dehydration reaction
H
OH
OH
OH
Short polymer
Unlinked monomer
Dehydration
Dehydratio
reaction
n reaction
Longer polymer
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H2O
OH
O
H
H
H
Figure 3.3A
H
H
• Polymers are broken down to monomers
–
By the reverse process, hydrolysis
H2O
H
OH
Hydrolysis
H
OH
OH
Figure 3.3B
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H
CARBOHYDRATES
3.4 Monosaccharides are the simplest
carbohydrates
• The carbohydrate monomers
–
Are monosaccharides
Figure 3.4A
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• A monosaccharide has a formula that is a multiple
of CH2O
–
And contains hydroxyl groups and a
carbonyl group
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• The monosaccharides glucose and fructose are
isomers
–
That contain the same atoms but in different
arrangements
H
O
H
C
H
C
OH
C
O
C
H
H
C
OH
HO
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
C
OH
H
Figure 3.4B
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Glucose
HO
H
Fructose
• Monosaccharides can also occur as ring structures
6 CH2OH
H
5C
CH2OH
O
H
H
H
C 1
4C
OH
OH
3C
H
OH
O
H
OH
H
OH
HO
C2
H
H
H
O
OH
OH
Structural
formula
Figure 3.4C
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Abbreviated
structure
Simplified
structure
3.5 Cells link two single sugars to form
disaccharides
• Monosaccharides can join to form disaccharides
–
Such as sucrose (table sugar) and maltose
(brewing sugar)
CH2OH
CH2OH
O
O
H
HO
H
H
H
OH
H
H
OH
HO
OH
H
H
H
OH
Glucose
OH
H
OH
Glucose
H2O
CH2OH
H
HO
Figure 3.5
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CH2OH
O
H
OH
H
H
OH
H
H
O
Maltose
O
H
OH
H
H
OH
H
OH
CONNECTION
3.6 How sweet is sweet?
• Various types of molecules, including nonsugars
–
Taste sweet because they bind to “sweet”
receptors on the tongue
Table 3.6
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3.7 Polysaccharides are long chains of sugar units
• Polysaccharides are polymers of monosaccharides
–
Linked together by dehydration reactions
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• Starch and glycogen are polysaccharides
–
That store sugar for later use
• Cellulose is a polysaccharide found in plant cell walls
O
Cellulose fibrils in
a plant cell wall
O
O
O
O
O
O
O
O
O
O
O
O
O
CELLULOSE
OO
OO
O OH
OO
O OH
OO
O
OO
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O
GLYCOGEN
O O
Figure 3.7
O
O O
O
Cellulose
molecules
O
O
O
Glycogen
granules in
muscle
tissue
Glucose
monomer
STARCH
Starch granules in
potato tuber cells
OO
OO
O O
O
O O
O
LIPIDS
3.8 Fats are lipids that are mostly energy-storage
molecules
• Lipids are diverse compounds
–
That consist mainly of carbon and hydrogen
atoms linked by nonpolar covalent bonds
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• Lipids are grouped together
– Because they are hydrophobic
Figure 3.8A
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• Fats, also called triglycerides
–
Are lipids whose main function is energy storage
–
Consist of glycerol linked to three fatty acids
H
H
H C
C
OH OH
Figure 3.8B
H
H
C H
OH
Glycerol
HO
C O
H2O
CH2
CH2
CH2
CH2
CH2
Fatty acid
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Figure 3.8C
H
H
H
C
C
C
O
O
O
C
O C
O C
H
O
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH3
CH
CH2
CH2
CH2
CH2
CH2
CH2
CH3
3.9 Phospholipids, waxes, and steroids are lipids
with a variety of functions
• Phospholipids are a major component of cell
membranes
• Waxes form waterproof coatings
• Steroids are often hormones
H3C
CH3
CH3
Figure 3.9
HO
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CH3
CH3
CONNECTION
3.10 Anabolic steroids pose health risks
• Anabolic steroids
– Are synthetic variants of testosterone
– Can cause serious health problems
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PROTEINS
3.11 Proteins are essential to the structures and
activities of life
• A protein
– Is a polymer constructed from amino acid
monomers
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• Proteins
–
Are involved in almost all of a cell’s activities
• As enzymes
–
They regulate chemical reactions.
Figure 3.11
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3.12 Proteins are made from amino acids linked
by peptide bonds
• Protein diversity
– Is based on different arrangements of a
common set of 20 amino acid monomers
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Each amino acid contains
–
An amino group
–
A carboxyl group
–
An R group, which distinguishes each of the
20 different amino acids
H
O
H
N
C
H
C
OH
R
Amino
group
Figure 3.12A
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Carboxyl (acid)
group
• Each amino acid has specific properties
– Based on its structure
H
H
H
O
N
H
C
H
C
CH2
O
N
OH
C
H
O
C
N
OH
H
CH
CH3
H
OH
CH2
CH2
OH
C
OH
Serine (Ser)
Hydrophobic
Figure 3.12B
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C
H
CH3
Leucine (Leu)
C
O
Aspartic acid (Asp)
Hydrophilic
• Cells link amino acids together
–
By dehydration synthesis
• The bonds between amino acid monomers
–
Are called peptide bonds
Carboxyl
group
Peptide
bond
Amino
group
H
H
H
O
N
H
C
C
H
+
OH
O
N
C
Dehydration
reaction
H
C
H
N
OH
R
R
Amino acid
Amino acid
H2O
H
H
O
C
C
R
H
N
C
H
R
Dipeptide
Figure 3.12C
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O
C
OH
3.13 A protein’s specific shape determines its
function
• A protein consists of one or more polypeptide
chains
–
Folded into a unique shape that determines
the protein’s function
Groove
Figure 3.13A
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Groove
Figure 3.13B
3.14 A protein’s shape depends on four levels of
structure
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Primary Structure
• A protein’s primary structure
–
Is the sequence of amino acids forming its
polypeptide chains
Levels of Protein Structure
Leu Met
Pro
Primary structure
Gly
Thr
Gly Glu
Cys
Ser Lys
Asn Val
Val
Lys
Val
Ala
Leu Asp Ala Val Arg Gly Ser Pro
Amino acids
Figure 3.14A
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Ala
Ile
Val
His Val
Phe
Arg
Secondary structure
• A protein’s secondary structure
–
Is the coiling or folding of the chain,
stabilized by hydrogen bonding
Amino acids
Hydrogen
bond
C
C
N H
O C
Secondary structure
C
O C
N H
N H O C
C
C
C
H O
N H
O C
C
N
N H
O C
N H O C
R
C
H C
N H O
O C
C
C
N H
Alpha helix
Figure 3.14B
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O H
H
O
N C CN
H
R CC N C CN
H
CC
O
H
O
O
H
O
C N CC
N
C
C H
H O C C N CN
H
O C
C
C
N
H
O
H
O
N C CN
H
CC N C C N
H
C
O
H
O
O
H
O
C N CC
N
H
C N C
H O C
CN
H
O C
Pleated sheet
Tertiary Structure
• A protein’s tertiary structure
–
Is the overall three-dimensional shape of a
polypeptide
Tertiary structure
Polypeptide
(single subunit
of transthyretin)
Figure 3.14C
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Quaternary Structure
• A protein’s quaternary structure
–
Results from the association of two or more
polypeptide chains
Polypeptide
chain
Quaternary structure
Transthyretin, with
four identical
polypeptide subunits
Figure 3.14D
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Collagen
TALKING ABOUT SCIENCE
3.19 Linus Pauling contributed to our understanding
of the chemistry of life
• Linus Pauling made important contributions
–
To our understanding of protein structure
and function
Figure 3.15
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NUCLEIC ACIDS
3.20 Nucleic acids are information-rich polymers of
nucleotides
• Nucleic acids such as DNA and RNA
–
Serve as the blueprints for proteins and thus
control the life of a cell
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• The monomers of nucleic acids are nucleotides
–
Composed of a sugar, phosphate, and
nitrogenous base
H
H
N
N
N
H
OH
O
P
N
O
CH2
Nitrogenous
base (A)
O

O
Phosphate
group
H
H
H
H
OH
Figure 3.16A
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Sugar
N
H
H
• The sugar and phosphate
–
Form the backbone for the nucleic acid or
polynucleotide
A
T
C
G
T
Figure 3.16B
Sugar-phosphate
backbone
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Nucleotide
• DNA consists of two polynucleotides
–
Twisted around each other in a double helix
C
A
C
C
T
G
G
A
T
C
G
A
T
T
A
Base
pair
G
T
A
A
T
Figure 3.16C
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A
C
T
• RNA, by contrast
–
Is a single-stranded polynucleotide
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• Stretches of a DNA molecule called genes
–
Program the amino acid sequences of
proteins
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