Transcript Bio-201-chapter-5-MEC

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 5
The Structure and Function of
Large Biological Molecules
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Figure 5.1
Concept 5.1: Macromolecules are polymers,
built from monomers
• polymer
• monomers
• Three of the four classes of life’s organic
molecules are polymers
– Carbohydrates
– Proteins
– Nucleic acids
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The Synthesis and Breakdown of Polymers
• dehydration reaction
• hydrolysis
Animation: Polymers
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Figure 5.2a
(a) Dehydration reaction: synthesizing a polymer
1
2
3
Unlinked monomer
Short polymer
Dehydration removes
a water molecule,
forming a new bond.
1
2
3
Longer polymer
4
Figure 5.2b
(b) Hydrolysis: breaking down a polymer
1
2
3
Hydrolysis adds
a water molecule,
breaking a bond.
1
2
3
4
Concept 5.2: Carbohydrates serve as fuel
and building material
• Carbohydrates
Monosaccharides - or single
sugars
Polysaccharides - polymers
composed of many sugar building
blocks
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Sugars
• Monosaccharides – 1:2:1 ratio CHO
classified by
– The location of the carbonyl group (as
aldose or ketose)
– The number of carbons in the carbon
skeleton
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Figure 5.3
Aldoses (Aldehyde Sugars)
Ketoses (Ketone Sugars)
Trioses: 3-carbon sugars (C3H6O3)
Glyceraldehyde
Dihydroxyacetone
Pentoses: 5-carbon sugars (C5H10O5)
Ribose
Ribulose
Hexoses: 6-carbon sugars (C6H12O6)
Glucose
Galactose
Fructose
Figure 5.3c
Aldose (Aldehyde Sugar)
Ketose (Ketone Sugar)
Hexoses: 6-carbon sugars (C6H12O6)
Glucose
Galactose
Fructose
Figure 5.4
1
2
6
6
5
5
3
4
4
5
1
3
6
(a) Linear and ring forms
6
5
4
1
3
2
(b) Abbreviated ring structure
2
4
1
3
2
Figure 5.5
1–4
glycosidic
1 linkage 4
Glucose
Glucose
Maltose
(a) Dehydration reaction in the synthesis of maltose
1–2
glycosidic
1 linkage 2
Glucose
Fructose
(b) Dehydration reaction in the synthesis of sucrose
Sucrose
Polysaccharides
• Polysaccharides
storage
structural roles
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Storage Polysaccharides
• Starch - glucose monomers
• stores surplus starch as granules
within chloroplasts and other
plastids
• simplest form of starch is amylose
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Figure 5.6
Chloroplast
Starch granules
Amylopectin
Amylose
(a) Starch:
1 m
a plant polysaccharide
Mitochondria
Glycogen granules
Glycogen
(b) Glycogen:
0.5 m
an animal polysaccharide
• Glycogen is a storage polysaccharide in
animals
• Humans and other vertebrates store
glycogen mainly in liver and muscle cells
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Structural Polysaccharides
• cellulose is a major component of the tough
wall of plant cells
• polymer of glucose with different glycosidic
linkages differ
• The difference is based on two ring forms for
glucose: alpha () and beta ()
Animation: Polysaccharides
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Figure 5.7
(a)  and  glucose
ring structures
4
1
4
 Glucose
 Glucose
1 4
(b) Starch: 1–4 linkage of  glucose monomers
1
1 4
(c) Cellulose: 1–4 linkage of  glucose monomers
Figure 5.8
Cellulose
microfibrils in a
plant cell wall
Cell wall
Microfibril
10 m
0.5 m
Cellulose
molecules
 Glucose
monomer
• Enzymes that digest starch by hydrolyzing 
linkages can’t hydrolyze  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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Figure 5.9
The structure
of the chitin
monomer
Chitin forms the exoskeleton
of arthropods.
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
• do not form polymers
• hydrophobic because they consist mostly of
hydrocarbons, which form nonpolar covalent
bonds
• important lipids are fats, phospholipids, and
steroids
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Figure 5.10
Fatty acid
(in this case, palmitic acid)
Glycerol
(a) One of three dehydration reactions in the synthesis of a fat
Ester linkage
(b) Fat molecule (triacylglycerol)
Figure 5.11
(a) Saturated fat
Structural
formula of a
saturated fat
molecule
Space-filling
model of stearic
acid, a saturated
fatty acid
(b) Unsaturated fat
Structural
formula of an
unsaturated fat
molecule
Space-filling model
of oleic acid, an
unsaturated fatty
acid
Cis double bond
causes bending.
• Hydrogenation
• trans fats
• Energy storage
• Omega-3
• Adipose tissue
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Hydrophobic tails
Hydrophilic head
Figure 5.12
Choline
Phosphate
Glycerol
Fatty acids
Hydrophilic
head
Hydrophobic
tails
(a) Structural formula
(b) Space-filling model
(c) Phospholipid symbol
Hydrophobic tails
Hydrophilic head
Figure 5.12a
(a) Structural formula
Choline
Phosphate
Glycerol
Fatty acids
(b) Space-filling model
Figure 5.13
Hydrophilic
head
Hydrophobic
tail
WATER
WATER
Figure 5.14
Concept 5.4: Proteins
• 50% of the dry mass of most cells
• functions
a. structural support
b. Storage
c. Transport
d. cellular communications
e. Movement
f. defense against foreign substances
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Figure 5.15a
Enzymatic proteins
Function: Selective acceleration of chemical reactions
Example: Digestive enzymes catalyze the hydrolysis
of bonds in food molecules.
Enzyme
Figure 5.15b
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
Figure 5.15c
Hormonal proteins
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
Normal
blood sugar
Figure 5.15d
Contractile and motor proteins
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.
Actin
Muscle tissue
100 m
Myosin
Figure 5.15e
Defensive proteins
Function: Protection against disease
Example: Antibodies inactivate and help destroy
viruses and bacteria.
Antibodies
Virus
Bacterium
Figure 5.15f
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 cell membranes.
Transport
protein
Cell membrane
Figure 5.15g
Receptor proteins
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.
Signaling
molecules
Receptor
protein
Figure 5.15h
Structural 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.
Collagen
Connective
tissue
60 m
Amino Acid Monomers
• carboxyl and amino groups
• differ in their properties due to
differing side chains, called R
groups
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Figure 5.UN01
Side chain (R group)
 carbon
Amino
group
Carboxyl
group
Figure 5.16
Nonpolar side chains; hydrophobic
Side chain
(R group)
Glycine
(Gly or G)
Alanine
(Ala or A)
Methionine
(Met or M)
Isoleucine
(Ile or I)
Leucine
(Leu or L)
Valine
(Val or V)
Phenylalanine
(Phe or F)
Tryptophan
(Trp or W)
Proline
(Pro or P)
Polar side chains; hydrophilic
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Electrically charged side chains; hydrophilic
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Glutamine
(Gln or Q)
Basic (positively charged)
Acidic (negatively charged)
Aspartic acid
(Asp or D)
Glutamic acid
(Glu or E)
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)
Figure 5.17
Peptide bond
New peptide
bond forming
Side
chains
Backbone
Amino end
(N-terminus)
Peptide
bond
Carboxyl end
(C-terminus)
Four Levels of Protein Structure
• primary structure
• Secondary structure
• Tertiary
• Quaternary
Animation: Protein Structure Introduction
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Figure 5.20a
Primary structure
Amino
acids
Amino end
Primary structure of transthyretin
Carboxyl end
Figure 5.20b
Tertiary
structure
Secondary
structure
Quaternary
structure
 helix
Hydrogen bond
 pleated sheet
 strand
Hydrogen
bond
Transthyretin
polypeptide
Transthyretin
protein
Figure 5.20c
Secondary structure
 helix
 pleated sheet
Hydrogen bond
 strand, shown as a flat
arrow pointing toward
the carboxyl end
Hydrogen bond
• Tertiary structure is determined by
interactions between R groups
• hydrogen bonds
• ionic bonds
• hydrophobic interactions
• van der Waals interactions
• disulfide bridges may reinforce the protein’s
structure
Animation: Tertiary Protein Structure
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Figure 5.20f
Hydrogen
bond
Hydrophobic
interactions and
van der Waals
interactions
Disulfide
bridge
Ionic bond
Polypeptide
backbone
Figure 5.20g
Quaternary structure
Transthyretin
protein
(four identical
polypeptides)
Figure 5.20h
Collagen
Figure 5.20i
Heme
Iron
 subunit
 subunit
 subunit
 subunit
Hemoglobin
What Determines Protein Structure?
• This loss of a protein’s native structure is
called denaturation
• A denatured protein is biologically inactive
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Figure 5.22
tu
Normal protein
Denatured protein
Figure 5.23b
Polypeptide
Correctly
folded
protein
Steps of Chaperonin 2 The cap attaches, causing 3 The cap comes
Action:
the cylinder to change
off, and the
1 An unfolded polyshape in such a way that
properly folded
peptide enters the
it creates a hydrophilic
protein is
cylinder from
environment for the
released.
one end.
folding of the polypeptide.
Figure 5.25-1
DNA
1 Synthesis of
mRNA
mRNA
NUCLEUS
CYTOPLASM
Figure 5.25-2
DNA
1 Synthesis of
mRNA
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into
cytoplasm
Figure 5.25-3
DNA
1 Synthesis of
mRNA
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into
cytoplasm
Ribosome
3 Synthesis
of protein
Polypeptide
Amino
acids
Figure 5.26
5 end
Sugar-phosphate backbone
Nitrogenous bases
Pyrimidines
5C
3C
Nucleoside
Nitrogenous
base
Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Purines
5C
1C
5C
3C
Phosphate
group
3C
Sugar
(pentose)
Guanine (G)
Adenine (A)
(b) Nucleotide
Sugars
3 end
(a) Polynucleotide, or nucleic acid
Deoxyribose (in DNA)
(c) Nucleoside components
Ribose (in RNA)
Figure 5.27
5
3
Sugar-phosphate
backbones
Hydrogen bonds
Base pair joined
by hydrogen
bonding
3
5
(a) DNA
Base pair joined
by hydrogen bonding
(b) Transfer RNA
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
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