Transcript Topic 4: Biochemistry and Marcomolecules

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Structure and Function of Large
Biological Molecules
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Macromolecules

4 main types: carbohydrates, lipids, proteins, nucleic acids

Large molecules typically made of smaller subunits

Carbs, Nucleic acids, proteins = Polymers – built from
monomers
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Synthesizing and Decomposing
Macromolecules:
Both processes use enzymes!

Dehydration Synthesis: “adding”
monomers together to form a
polymer.

Removal of an H2O molecule
covalently bonds the monomers.
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Hydrolysis: Breaking down of
polymers into smaller subunits
using water.

The H bonding to one
monomer and the OH bonding
to the other.
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Carbohydrates
Sugars and sugar chains –
the fuel and building
materials of life
Monosaccharides:
Simple Sugars
Sugar units have empirical
formula: CH2O
C chains range from 3-7
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Enantiomers – different sugars!
5-6 C typically are aromatic!
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Glucose is Life
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C1 and C5 bond to form ring
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Glucose is a primary cellular fuel source for respiration
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Glucose is also used as a building block for many other
macromolecules

Can be stored for later use as di- and polysaccharides
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2 forms of the rings α and β
http://pslc.ws/macrog/kidsmac/toon_glu.htm
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α-glucose and β-glucose
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Disaccharides Through
Dehydration Synthesis
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2 monosaccharides bonded
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Linkages are named by the
carbons that bond
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Glycosidic linkage formed by
dehydration synthesis
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Maltose is a 1-4 glycosidic
linkage
Disaccharides: maltose,
sucrose, lactose
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Sucrose is a 1-2 glycosidic
linkage
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Types of Glycosidic Linkages
1–4
glycosidic
linkage
Maltose
1–2
glycosidic
linkage
Sucrose
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Polysaccharides – huge chains of
monosaccharides
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Each monomer is added
through dehydration synthesis
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Huge chains are good for
storage and even structure
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Function of the polydetermined by type of linkage
and sugar monomers
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Storage Polysaccharides
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Plants create starch for
storage
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Glucose monomers =
stored energy
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Stored in plastids
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Formed by 1-4 glycosidic
linkages
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Animals
synthesize
glycogen
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Glucose
monomers
– high
branched
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Stored in
liver and
muscle
Storage Polysaccharides
Structural Polysaccharides
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Cellulose – major
component of cell
walls
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Most abundant
organic molecule
on earth
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Glucose monomers
– different linkages!
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Different forms of
glucose but same 14 linkage!
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Cellulose: Tough Cell Walls… Why?
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Cellulose is straight chains
and never branched
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Form parallel chains
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Different enzymes to digest!
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Fiber 
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Chitin = exoskeletons
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Lipids
Hydrophobic, diverse
molecules
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Lipid Basics: Hydrophobic energy
chains
Lipids are diverse in function but
similar in their hydrophobicity
Typically have large regions that are
hydrocarbon chains
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Building Blocks of Fats
 Fatty
acid chains
 Glycerol
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Triacylglycerol (TAGs)
AKA Triglycerides
Ester linkage!
Dehydration Synthesis! x3
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Saturated and Unsaturated Fats
Naturally occurring fatty
acids have cis double bonds
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Cis vs Trans Fats
Figure 5.12
Hydrophobic tails
Hydrophilic head
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Choline
Phosphate
Glycerol
Fatty acids
Hydrophilic
head
Hydrophobic
tails
(a) Structural formula
(b) Space-filling model
(c) Phospholipid symb
Figure 5.13
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Hydrophilic
head
Hydrophobic
tail
WATER
WATER
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Steroids
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Steroids have 4 carbon ring structures
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Can be hormones or cholesterol
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Proteins
Multiple units, multiple
uses
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Functions of Protein
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Proteins account for ~50% of
the dry mass of most cells
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Proteins act as catalysts,
play roles in defense,
storage, transport, and
cellular communication
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Greatest diversity in
structure and function
Figure 5.15-a
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Enzymatic proteins
Function: Selective acceleration of chemical reactions
Example: Digestive enzymes catalyze the hydrolysis
of bonds in food molecules.
Defensive proteins
Function: Protection against disease
Example: Antibodies inactivate and help destroy
viruses and bacteria.
Antibodies
Enzyme
Virus
Storage proteins
Bacterium
Transport 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.
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
Ovalbumin
Amino acids
for embryo
Cell membrane
Figure 5.15-b
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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
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Protein Building Blocks - Peptides

All proteins are made of 20
different amino acids
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Amino end
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Carboxyl end
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R = functional group
α CARBON
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Proteins are Polypeptides
 Polymers
of peptides
are made through the
formation of peptide
bond
 Carboxyl
end of one AA
bonds to the amino end
of adjacent AA
 Dehydration
reaction to
form peptide bond
N
terminus (+) and C
terminus (-)
Figure 5.16
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Nonpolar side chains; hydrophobic
Side chain
(R group)
Glycine
(Gly or G)
Alanine
(Ala or A)
Methionine
(Met or M)
Phenylalanine
(Phe or F)
Isoleucine
(Ile or I)
Leucine
(Leu or L)
Valine
(Val or V)
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 5.16a
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Nonpolar side chains; hydrophobic
Side chain
Glycine
(Gly or G)
Methionine
(Met or M)
Alanine
(Ala or A)
Valine
(Val or V)
Phenylalanine
(Phe or F)
Leucine
(Leu or L)
Tryptophan
(Trp or W)
Isoleucine
(Ile or I)
Proline
(Pro or P)
Figure 5.16b
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Polar side chains; hydrophilic
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Tyrosine
(Tyr or Y)
Asparagine
(Asn or N)
Glutamine
(Gln or Q)
Figure 5.16c
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Electrically charged side chains; hydrophilic
Basic (positively charged)
Acidic (negatively charged)
Aspartic acid Glutamic acid
(Glu or E)
(Asp or D)
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)
Figure 5.17
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Peptide bond
Dehydration synthesis
New peptide
bond forming
Side
chains
Backbone
Amino end
(N-terminus)
Side chains vary in their
charge, polarity, length
Peptide Carboxyl end
bond (C-terminus)
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Protein – Structure Dictates Function
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3D structure of each protein
is unique
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Structure dictates function
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Structure is determined due
to 4 levels of folding
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Most fundamental level of
folding is sequence of AA
Figure 5.19
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Antibody protein
Protein from flu virus
Primary Structure
AA Sequence
 Sequence
of AA
 Read
in order from
N to C
 Dictates
secondary,
tertiary, quaternary
levels
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Secondary Structure
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Regions of a
peptide chain
that are coiled
or folded into
patterns
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Regulated by H
bonding of
atoms in the
peptide
backbone
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α-Helix
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β-sheets
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Tertiary
Structure
Overall shape of a protein
Stabilized by R groups
and how they interact
Hydrophobic Interactions
Disulfide Bridges
Quaternary Structure
The interaction
of multiple
polypeptide
chains
Forms a
functional
protein
Separate peptide
chains
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Chaperonins: Protein Folders
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Protein Structure in a Cell
 Folding
 Other
is spontaneous
proteins aid in this process
 Denaturation
– unraveling/misfolding of a protein
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Nucleic
Acids
Blueprints of life
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Nucleotides
 Monomers
of
nucleotides
2
types: DNA and
RNA
 Deoxyribonucleic
acid
 Ribonucleic acid
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DNA to RNA to Protein
 Genetic
material
 Inherited
 Codes
 DNA
for all genes
 RNA  Protein
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Nucleotides
Types
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2 Types of sugars
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Ribose
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Deoxyribose
2 Categories of N bases
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Purines (Pure As Gold)
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A and G
Pyrimidines
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C, T, U
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Polynucleotides – Nucleic Acids
 Nucleotides
are
linked by a
phosphodiester bond
 Adjacent
sugars are
linked from 5’ end to
first sugar to 3’ of next
sugar
N
Bases point inwards
and provide
“sequence” of DNA
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Structure
of DNA
 Double
helix
 Sugar-
phosphates are
antiparallel
 Bases
pair 1
purine to 1
pyrimidine