1. Chapter 5: The Macromolecules of Life
• Within cells, small organic molecules are joined together to
form larger molecules
• Macromolecules are large molecules composed of thousands
of covalently connected atoms
• A polymer is a long molecule consisting of many similar
building blocks called monomers
e.g. proteins
2. Three of the four classes of life’s organic molecules are
polymers:
– Carbohydrates e.g. starch
– Proteins e.g. enzymes
– Nucleic acids e.g. DNA
Not really a polymer, but large
– Lipids e.g fats
3. The Synthesis and Breakdown of
Polymers
• Monomers form larger molecules by condensation
reactions called dehydration reactions (two
monomers bond through loss of a water)
• Polymers are disassembled to monomers by
hydrolysis, a reaction that is essentially the reverse
of the dehydration reaction
4. Figure 5.2
(a) Dehydration reaction: synthesizing a polymer
1 2 3
1 2 3 4
1 2 3 4
Dehydration removes a water
molecule, forming a new bond.
Short polymer Unlinked monomer
H2O
Longer polymer
H2O
(b) Hydrolysis: breaking down a polymer
Hydrolysis adds a water
molecule, breaking a bond.
1 2 3
5. Concept 5.2: Carbohydrates serve
as fuel and building material
• Carbohydrates include sugars and the polymers of sugars
• The simplest carbohydrates are monosaccharides, or single
sugars
• Carbohydrate macromolecules are polysaccharides, polymers
composed of many sugar building blocks
• Monosaccharides have molecular formulas that are usually
multiples of CH2O
• Glucose is the most common monosaccharide
• Monosaccharides are classified by location of the carbonyl
group and by number of carbons in the carbon skeleton
7. Figure 5.4
(a) Linear and ring forms
(b) Abbreviated ring structure
Be able to number the ring of glucose and ribose correctly!
8. LE 5-5
Glucose
Maltose
Fructose Sucrose
Glucose Glucose
Dehydration
reaction in the
synthesis of maltose
Dehydration
reaction in the
synthesis of sucrose
1–4
glycosidic
linkage
1–2
glycosidic
linkage
•A disaccharide is formed when a dehydration reaction joins two monosaccharides
•This covalent bond is called a glycosidic linkage
Be able to construct maltose, sucrose, and lactose if given
glucose, galactose, and fructose.
Alpha 1,4
Alpha 1,2
10. 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
• Starch, a storage polysaccharide of plants, consists
entirely of glucose monomers
• Plants store surplus starch as granules within
chloroplasts and other plastids
11. LE 5-6a
Chloroplast Starch
1 µm
Amylose
Starch: a plant polysaccharide
Amylopectin
α-14 linked glucose α 14 linked glucose
And α 16 branching
12. LE 5-6b
Mitochondria Glycogen granules
0.5 µm
Glycogen
Glycogen: an animal polysaccharide
•Glycogen is a storage
polysaccharide in
animals
•Humans and other
vertebrates store
glycogen mainly in liver
and muscle cells
•Same branching as
amylopectin except
more frequent and
shorter branches
13. LE 5-7
α Glucose
α and β glucose ring structures
β Glucose
Starch: 1–4 linkage of α glucose monomers.
Cellulose: 1–4 linkage of β glucose monomers.
•Like starch, cellulose is a
polymer of glucose, but the
glycosidic linkages differ
•The difference is based on
two ring forms for glucose:
alpha (α) and beta (β)
•Note placement of hydroxyls
on monomeric units in the
different polymers
14. • Polymers with alpha glucose are helical
• Polymers with beta glucose are straight
• In straight structures, H atoms on one strand can bond with
OH groups on other strands
• Parallel cellulose molecules held together this way are
grouped into microfibrils, which form strong building
materials for plants
17. •Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze
beta 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
18. •Chitin, another structural polysaccharide, is found in the exoskeleton
of arthropods (Beta linkage)
•Chitin also provides structural support for the cell walls of many
fungi
•Chitin can be used as surgical thread
19. Concept 5.3: Lipids
• Lipids are the one class of large biological molecules
that 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
20. Dehydration reaction in the synthesis of a fat
Glycerol
Fatty acid
(palmitic acid)
•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
Fats
21. Ester linkage
Fat molecule (triacylglycerol)
In a fat, three fatty acids are joined to glycerol by an ester linkage,
creating a triacylglycerol, or triglyceride
22. •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
•Most animal fats are saturated; plant and
fish fats are generally unsaturated
•Saturated fats are solid at room
temperature
•A diet rich in saturated fats may contribute
to cardiovascular disease through plaque
deposits
23. Figure 5.10
(a) Saturated fat (b) Unsaturated fat
Structural
formula
of a saturated
fat molecule
Space-filling
model of
stearic acid,
a saturated
fatty acid
Structural
formula of an
unsaturated
fat molecule
Space-filling
model of oleic
acid, an
unsaturated
fatty acid Cis double
bond causes
bending.
24. Structural formula Space-filling model Phospholipid symbol
Hydrophilic
head
Hydrophobic
tails
Fatty acids
Choline
Phosphate
Glycerol
HydrophobictailsHydrophilicheadPhospholipids 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
26. • Steroids are lipids characterized by a carbon
skeleton consisting of four fused rings
• Cholesterol, an important steroid, is a component in
animal cell membranes
27. 1. Lipids cannot be considered
polymers because
a. they contain polar covalent bonds.
b. their structure includes carbon rings.
c. they can be artificially created.
d. their monomers are connected via ionic
bonds.
e. they are not composed of monomer
subunits.
28. 1. Lipids cannot be considered
polymers because
a. they contain polar covalent bonds.
b. their structure includes carbon rings.
c. they can be artificially created.
d. their monomers are connected via ionic
bonds.
e. they are not composed of monomer
subunits.
30. Figure 5.13a
Enzymatic proteins
Function: Selective acceleration of
chemical reactions
Example: Digestive enzymes catalyze the
hydrolysis of bonds in food molecules.
Enzyme
Storage proteins
Function: Storage of amino acids
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.
Ovalbumin Amino acids
for embryo
Defensive proteins
Function: Protection against disease
Example: Antibodies inactivate and help
destroy viruses and bacteria.
Virus
Antibodies
Bacterium
Transport proteins
Function: Transport of substances
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 membranes, as shown here.
Transport
protein
Cell membrane
31. Figure 5.13b
Function: Coordination of an organism’s
activities
Example: Insulin, a hormone secreted by the
pancreas, causes other tissues to take up
glucose, thus regulating blood sugar,
concentration.
High
blood sugar
Insulin
secreted
Hormonal proteins
Normal
blood sugar
Function: Response of cell to chemical
stimuli
Example: Receptors built into the
membrane of a nerve cell detect
signaling molecules released by other
nerve cells.
Receptor proteins
Signaling
molecules
Receptor
protein
Function: Movement
Examples: Motor proteins are responsible
for the undulations of cilia and flagella.
Actin and myosin proteins are responsible
for the contraction of muscles.
Contractile and motor proteins
Function: Support
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.
Structural proteins
Muscle
tissue
30 µm
Actin MyosinActin
60 µm
Connective
tissue
Collagen
32. Amino Acid Monomers
• Amino acids are organic molecules with carboxyl
and amino groups
• Amino acids differ in their properties due to
differing side chains, called R groups
• Cells use 20 amino acids to make thousands of
proteins
Polypeptides are polymers of amino acids
A protein consists of one or more polypeptides
Polypeptides
34. Figure 5.14
Nonpolar side chains; hydrophobic
Side chain (R group)
Glycine
(Gly or G)
Alanine
(Ala or A)
Valine
(Val or V)
Leucine
(Leu or L)
Isoleucine
(Ile or I)
Proline
(Pro or P)
Tryptophan
(Trp or W)
Phenylalanine
(Phe or F)
Methionine
(Met or M)
Polar side chains; hydrophilic
Electrically charged side chains; hydrophilic
Aspartic acid
(Asp or D)
Glutamic acid
(Glu or E)
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)
Glutamine
(Gln or Q)
Acidic (negatively charged)
Basic (positively charged)
Asparagine
(Asn or N)
Tyrosine
(Tyr or Y)
Cysteine
(Cys or C)
Threonine
(Thr or T)
Serine
(Ser or S)
Know how to
draw:
glycine,
valine,
cysteine,
glutamine,
glutamic
acid, lysine
and put them
into dipeptide
form
35. Amino Acid Polymers
Amino acids
are linked by
peptide bonds
A polypeptide
is a polymer of
amino acids
36. Figure 5.16
(a) A ribbon model (b) A space-filling model (c) A wireframe model
Groove
Groove
Target
molecule
Different models have different uses e.g. secondary structure or amino-
acid contact sites
37. Four Levels of Protein Structure
• 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 when a protein
consists of multiple polypeptide chains
39. LE 5-20d
Hydrophobic
interactions and
van der Waals
interactions
Polypeptide
backbone
Disulfide bridge
Ionic bond
Hydrogen
bond
Tertiary structure is
determined by interactions
between R groups, rather
than interactions between
backbone constituents
These interactions
between R groups include
hydrogen bonds, ionic
bonds, hydrophobic
interactions, and van der
Waals interactions
Strong covalent bonds
called disulfide bridges
may reinforce the protein’s
conformation
40. Sickle-Cell Disease: A Simple Change in
Primary Structure
• A slight change in primary structure can affect a
protein’s conformation and ability to function
• Sickle-cell disease, an inherited blood disorder,
results from a single amino acid substitution in the
protein hemoglobin
41. Molecules do not associate
with one another; each carries oxygen.
42. 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
43. The Protein-Folding Problem
• It is hard to predict a protein’s conformation from its
primary structure
• Most proteins probably go through several states on
their way to a stable conformation
• Chaperonins are protein molecules that assist the
proper folding of other proteins
44. Figure 5.21
Hollow
cylinder
Cap
Chaperonin
(fully
assembled)
Polypeptide
1 An unfolded
polypeptide
enters the
cylinder
from
one end.
2 Cap attachment
causes the
cylinder to
change shape,
creating a
hydrophilic
environment
for polypeptide
folding.
3 The cap
comes off,
and the
properly
folded
protein is
released.
Correctly folded
protein
45. LE 5-24a
Photographic film
Diffracted X-rays
X-ray
source
X-ray
beam
X-ray
diffraction pattern
Crystal
•Scientists use X-ray crystallography to determine a protein’s
conformation
•Another method is nuclear magnetic resonance (NMR) spectroscopy,
which does not require protein crystallization
47. 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
• Protein synthesis occurs in ribosomes
49. The Structure 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 a phosphate group
• The portion of a nucleotide without the phosphate
group is called a nucleoside
50. LE 5-26a
5′ end
3′ end
Nucleoside
Nitrogenous
base
Phosphate
group
Nucleotide
Polynucleotide, or
nucleic acid
Pentose
sugar
51. LE 5-26b
Nitrogenous bases
Pyrimidines
Purines
Pentose sugars
Cytosine
C
Thymine (in DNA)
T
Uracil (in RNA)
U
Adenine
A
Guanine
G
Deoxyribose (in DNA)
Nucleoside components
Ribose (in RNA)
Be able to
recognize
each base &
the hydrogen
bonding
pattern
between base
pairs.
When given the
bases, sugars, and a
phosphate structure,
be able to construct a
nucleotide pair.
Pyrimidines are CUT!
53. Nucleotide Polymers
• Nucleotide polymers are linked together,
building a polynucleotide
• 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 on 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
54. The DNA Double Helix
• A DNA molecule has two polynucleotides spiraling
around an imaginary axis, forming a double helix
• In the DNA double helix, the two backbones run in
opposite 5´ to 3´ directions from each other, an
arrangement referred to as antiparallel
• One DNA molecule includes many genes
• The nitrogenous bases in DNA form hydrogen bonds in
a complementary fashion: A always with T, and G
always with C
55. LE 5-27
Sugar-phosphate
backbone
3′ end5′ end
Base pair (joined by
hydrogen bonding)
Old strands
Nucleotide
about to be
added to a
new strand
5′ end
New
strands
3′ end
5′ end3′ end
5′ end
56. 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
57. DNA and polypeptide sequences from closely related species are more similar to
each other than sequences from more distantly related species. For the remaining
questions, you will look at amino acid sequence data for the β polypeptide chain of
hemoglobin, often called β-globin. You will then interpret the data to hypothesize
whether the monkey or the gibbon is more closely related to humans.
In the alignment shown below, the letters give the sequences of the 146 amino acids
in β-globin from humans, rhesus monkeys, and gibbons. Because a complete
sequence would not fit on one line, the sequences are broken into segments. The
sequences for the three different species are aligned so that you can compare them
easily. For example, you can see that, for all three species, the first amino acid is “V”
(valine) and the 146th amino acid is “H” (histidine).
Create a cladogram for human, monkey, and gibbon based on data below.
58. The Theme of Emergent Properties in the
Chemistry of Life: A Review
• Higher levels of organization result in the emergence of new
properties
Explain the new properties for each of the 4 groups of
Biomolecules
(Hint: see page 90 for emergent properties overview)
• Organization is the key to the chemistry of life
Editor's Notes
Figure 5.2 The synthesis and breakdown of polymers
Figure 5.4 Linear and ring forms of glucose
Figure 5.6 Polysaccharides of plants and animals
Figure 5.10 Saturated and unsaturated fats and fatty acids
Answer: E
Answer: E
Figure 5.13a An overview of protein functions (part 1)
Figure 5.13b An overview of protein functions (part 2)
Figure 5.14 The 20 amino acids of proteins
Figure 5.16 Structure of a protein, the enzyme lysozyme
