Download Chapter 5 - macromolecules

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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.
Overview: The Molecules of Life
four classes of large biological molecules:
carbohydrates - polymer
lipids
proteins - polymer
nucleic acids - polymer
Polymer: made of many small parts
each part is a monomer
Many biological molecules are polymers
© 2011 Pearson Education, Inc.
Figure 5.UN02
Overview: The Molecules of Life
• Macromolecules = big molecules
usually a polymer
• Molecular structure and function are linked
» Change the structure or shape of
a molecule and you will destroy
it’s function
» “denature” = changing shape of
molecule (protein) so that it
doesn’t work anymore
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The Synthesis and Breakdown of Polymers
• dehydration reaction: making bonds
(synthesizing a molecule) by taking away water
Animation: Polymers
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The Synthesis and Breakdown of Polymers
• Breaking a polymer apart hydrolysis, a reaction
that is essentially the reverse of the dehydration
reaction
Animation: Polymers
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The Diversity of Polymers
• Macromolecules – many thousands of kinds
HO
– Species differences
– Individual differences
– Cell differences within organism
• small set of monomers can make MANY kinds
of monomers
– A small set of letter make MANY different words
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Concept 5.2: Carbohydrates serve as fuel
and building material
• Carbohydrates - sugars and their polymers
• “saccharides” – sugars
• monosaccharides
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Concept 5.2: Carbohydrates serve as fuel
and building material
•
•
•
•
Carbohydrates - sugars and their polymers
“saccharides” – sugars
Monosaccharides – 1 sugar
Disaccharide – molecule made of 2 sugars
• Polysaccharides – long chains of sugar
monomers
© 2011 Pearson Education, Inc.
Sugars
• Monosaccharides - CH2O-like formula
• Glucose (C6H12O6) is the most common
• Monosaccharides are classified by
– The number of carbons in the carbon skeleton
– The location of the carbonyl group (as aldose
or ketose)
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• Though often drawn as linear skeletons, in
aqueous solutions many sugars form rings
• Monosaccharides (especially glucose) serve
as a major fuel for cells and as raw material for
building molecules
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• A disaccharide is formed when a dehydration
reaction joins two monosaccharides
• This covalent bond is called a glycosidic
linkage
Animation: Disaccharide
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Polysaccharides
• Polysaccharides - storage and structural roles
• Polysaccharide structure and function
which sugar monomers
position of glycosidic linkages
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Storage Polysaccharides
• Starch, a storage polysaccharide of plants,
consists entirely of glucose monomers
• Plants store surplus starch as granules within
chloroplasts and other plastids
• The simplest form of starch is amylose
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• 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
• The polysaccharide cellulose is a major
component of the tough wall of plant cells
• Like starch but the glycosidic linkages differ
– Why we can’t digest cellulose
Animation: Polysaccharides
© 2011 Pearson Education, Inc.
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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• Chitin: structural polysaccharide of animals
– exoskeleton of arthropods
– cell walls of many fungi
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Concept 5.3: Lipids are a diverse group of
hydrophobic molecules
• Lipids – NOT A POLYMER
• hydrophobic (non-polar covalent bonds)
• 3 kinds of lipids in biology
– fats, phospholipids, and steroids
• Water dissolves things it can make polar
bonds with. Has trouble bonding with
lipids.
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Fats: glycerol + fatty acids
• water molecules bonds
to water, excluding 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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• Saturated fatty
acids
• maximum
number of
hydrogen atoms
• no double bonds
• Usually solid at
room temp
Animation: Fats
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• Unsaturated
fatty acids have
one or more
double bonds
• Each double
bond causes a
kink in the chain
• Usually liquid at
room temp
Animation: Fats
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• Cis vs. Trans
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• Essential fatty acids
– We can’t make them (must get from food; omega-3)
– Used in normal growth
– Protect against cardiovascular disease??
• Fats are used for energy storage
– Stored in adipose tissue
– Also cushion’s organs
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Phospholipids
• Glycerol + phosphate + two fatty acids
Hydrophilic
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hydrophobic
• The fatty acid tails are hydrophobic
• The heads are hydrophilic
• Tails point away from water
• The major component in membranes
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Steroids
• Steroids are lipids made of four carbon 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
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Steroids
• Steroids are lipids made of four carbon rings
• Some hormones are steroids
• Cholesterol, is also a steroid
– Used in animals membranes, but high levels in blood
may contribute to cardiovascular disease
© 2011 Pearson Education, Inc.
Concept 5.4: Proteins include a diversity of
structures, resulting in a wide range of
functions
• Used for EVERYTHING
• structural support, storage, transport, cellular
communications, movement, and defense
against foreign substances
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Protein Structure and Function
• A functional protein consists of one or more
polypeptides precisely twisted, folded, and
coiled into a unique shape
• If you change the shape, the protein stops
working.
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• Enzymes: proteins that speed up chemical
reactions (acts as a catalyst)
• Enzymes can perform their functions
repeatedly, functioning as workhorses that
carry out the processes of life
•Shape is crucial
to enzyme function
•If you denature it,
the enzyme stops
working
Animation: Enzymes
© 2011 Pearson Education, Inc.
Figure 5.15-a
Enzymatic proteins
Defensive proteins
Function: Selective acceleration of chemical reactions
Example: Digestive enzymes catalyze the hydrolysis
of bonds in food molecules.
Function: Protection against disease
Example: Antibodies inactivate and help destroy
viruses and bacteria.
Antibodies
Enzyme
Virus
Bacterium
Storage proteins
Transport proteins
Function: Storage of amino acids
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.
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.
Transport
protein
Ovalbumin
Amino acids
for embryo
Cell membrane
Figure 5.15-b
Hormonal proteins
Receptor 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
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.
High
blood sugar
Insulin
secreted
Normal
blood sugar
Receptor
protein
Signaling
molecules
Contractile and motor proteins
Structural 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.
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.
Actin
Myosin
Collagen
Muscle tissue
100 m
Connective
tissue
60 m
Animation: Structural Proteins
Animation: Storage Proteins
Animation: Transport Proteins
Animation: Receptor Proteins
Animation: Contractile Proteins
Animation: Defensive Proteins
Animation: Hormonal Proteins
Animation: Sensory Proteins
Animation: Gene Regulatory Proteins
© 2011 Pearson Education, Inc.
Amino Acids: protein building blocks
• Amino acids are organic molecules with
carboxyl and amino groups
• Amino acids differ in their properties due to
differing side chains, called R groups
© 2011 Pearson Education, Inc.
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)
Polypeptides: a chain of amino acids
• Polypeptides: are
unbranched polymers
built from the same set of
20 amino acids
• A protein has one or
more polypeptides
© 2011 Pearson Education, Inc.
Polypeptide: Amino Acid Polymers
• can be short or more than a thousand
monomers
• Each polypeptide has a carboxyl end (Cterminus) and an amino end (N-terminus)
© 2011 Pearson Education, Inc.
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
Animation: Protein Structure Introduction
© 2011 Pearson Education, Inc.
• A protein’s structure
determines its function
• The sequence of amino
acids determines a
protein’s three-dimensional
structure
• Primary structure, the
sequence of amino acids in
a protein
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• Primary structure, the sequence of amino
acids in a protein, is like the order of letters
in a long word
• Primary structure is determined by inherited
genetic information
Animation: Primary Protein Structure
© 2011 Pearson Education, Inc.
• secondary structure: 3-D shape in local
regions of peptide chain
• Caused by hydrogen bonds between parts of
the polypeptide backbone
• Typical secondary structures are a coil called
an  helix and a folded structure called a 
pleated sheet
Animation: Secondary Protein Structure
© 2011 Pearson Education, Inc.
• Tertiary structure is determined by
interactions between R groups
–
–
–
–
hydrogen bonds
ionic bonds
hydrophobic interactions
Van der Waals interactions
Strong covalent bonds called
disulfide bridges may
reinforce the protein’s
structure
Animation: Tertiary Protein Structure
© 2011 Pearson Education, Inc.
Quaternary structure: if there is more than one
polypeptide chains in protein
•Collagen is a fibrous protein
consisting of three
polypeptides coiled like a
rope
•Hemoglobin is a globular
protein consisting of four
polypeptides: two alpha and
two beta chains
Animation: Quaternary Protein Structure
© 2011 Pearson Education, Inc.
Sickle-Cell Disease: A Change in Primary
Structure
• Changing the primary structure can change the
shape and function of a protein
• Sickle-cell disease, an inherited blood
disorder, results from a single amino acid
substitution in the protein hemoglobin
© 2011 Pearson Education, Inc.
Figure 5.21
Sickle-cell hemoglobin
Normal hemoglobin
Primary
Structure
1
2
3
4
5
6
7
Secondary
and Tertiary
Structures
Quaternary
Structure
Function
Molecules do not
associate with one
another; each carries
oxygen.
Normal
hemoglobin
 subunit

Red Blood
Cell Shape

10 m


1
2
3
4
5
6
7
Exposed
hydrophobic
region
Sickle-cell
hemoglobin

 subunit

Molecules crystallize
into a fiber; capacity
to carry oxygen is
reduced.


10 m
What Determines Protein Structure?
• The chemical environment affects a protein
• Changing pH, salt concentration, temperature,
or other environmental factors can cause a
protein to unravel
• Denature: changing a protein away from its
natural shape
• A denatured protein is biologically inactive
• Alzheimer’s
• Parkinson’s
• Mad cow disease
© 2011 Pearson Education, Inc.
Protein Folding in the Cell
• It is hard to predict a protein’s structure from
its primary structure
• Most proteins probably go through several
stages on their way to a stable structure
• Chaperonins are protein molecules that
assist the proper folding of other proteins
© 2011 Pearson Education, Inc.
Concept 5.5: Nucleic acids store, transmit,
and help express hereditary information
• a nucleic acid polymer is made of monomers
called nucleotides
• Genes are instructions written in DNA (many
genes on each chromosome)
• The DNA sequence of a gene has
instructions to make a polypeptide
© 2011 Pearson Education, Inc.
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 on ribosomes
© 2011 Pearson Education, Inc.
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
The Components of Nucleic Acids
• Nucleic acids are chains of nucleotides
– pentose sugar
– phosphate groups
– a nitrogenous base
• Nucleoside: nucleotide without phosphate
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The Components of Nucleic Acids
• Nucleic acids are chains of nucleotides
– a nitrogenous base
– phosphate groups
– pentose sugar
• Nucleoside: nucleotide without phosphate
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• Nucleoside = nitrogenous base + sugar
• There are two families of nitrogenous bases
– Pyrimidines (cytosine, thymine, and uracil)
have a single six-membered ring
– Purines (adenine and guanine) have a sixmembered ring fused to a five-membered ring
• In DNA, the sugar is deoxyribose; in RNA, the
sugar is ribose
• Nucleotide = nucleoside + phosphate group
© 2011 Pearson Education, Inc.
Nucleotide Polymers
• Nucleotide polymers are linked together to build
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 abc…lmnop
• sugar-phosphate backbone (side of ladder) with
nitrogenous bases as rungs of ladder
• The sequence of bases along a DNA or mRNA
polymer is the genetic code, the instructions
– unique for each gene
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The Structures of DNA and RNA Molecules
• RNA molecules usually exist as single
polypeptide chains (exception: some viruses)
• DNA molecules have two chain,
– forming a double helix (twisty ladder)
• Antiparallel: DNA strands in opposite directions
• One DNA molecule includes many genes
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complementary base pairing
DNA
• adenine (A)  thymine (T)
• guanine (G)  cytosine (C)
RNA
• adenine (A)  Uracil (U)
• guanine (G)  cytosine (C)
© 2011 Pearson Education, Inc.
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
• DNA sequences: parents  offspring
• closely related species have more similar DNA
than distantly related species
• Molecular biology is used to assess evolutionary
kinship
• Why people are fighting about protista right now
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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
© 2011 Pearson Education, Inc.
Figure 5. UN12
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