Macromolecules
Chapter 5
Building Blocks
of Life
AP Biology
2007-2008
Macromolecules
 Smaller organic molecules join together
to form larger molecules

macromolecules
 4 major classes of
macromolecules:
carbohydrates
 lipids
 proteins
 nucleic acids

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Polymers
 Long molecules built by linking repeating
building blocks in a chain

monomers
 building blocks
 repeated small units

H 2O
covalent bonds
HO
H
HO
H
Dehydration synthesis
HO
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H
How to build a polymer
 Synthesis

joins monomers by “taking” H2O out
 one monomer donates OH–
 other monomer donates H+
 together these form H2O

H 2O
requires energy & enzymes
HO
H
Dehydration synthesis
HO
H
enzyme
Condensation reaction
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HO
H
How to build a polymer
H
H
H
H
monomer monomer monomer
Polymer
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H
H
H
How to break down a polymer
 Digestion

use H2O to breakdown polymers
 reverse of dehydration synthesis
 cleave off one monomer at a time
 H2O is used
 H+ & OH– attach to ends
requires enzymes
HO
 releases energy
H2O

enzyme
H
Hydrolysis
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Digestion
HO
H
HO
H
Numbered carbons
These will become
important!
C6'
5'C
O
4'C
C 1'
energy stored in C-C bonds
harvested in cellular respiration
C 3'
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C 2'
Simple & complex sugars
 Monosaccharides
simple 1 monomer sugars
 glucose

 Disaccharides
2 monomers
 sucrose

 Polysaccharides
large polymers
 starch

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CH2OH
H
O
H
OH
H
H
OH
HO
Glucose
H
OH
Building sugars
 Dehydration synthesis
monosaccharides
disaccharide
H2O
|
glucose
|
glucose
|
maltose
glycosidic linkage
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Building sugars
 Dehydration synthesis
monosaccharides
|
glucose
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H2O
|
fructose
disaccharide
|
sucrose
(table sugar)
Polysaccharides
 Polymers of sugars
costs little energy to build
 easily reversible = release energy

 Function:

energy storage
 Transfer energy to ATP
 starch (plants)
 Stored in plastids
 glycogen (animals)
 in liver & muscles

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structure
 cellulose (plants)
 chitin (arthropods & fungi)
Linear vs. branched polysaccharides
slow release
starch
(plant)
energy
storage
glycogen
(animal)
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fast
release
Branching =
Faster digestion!
Polysaccharide diversity
 Molecular structure determines function
in starch
in cellulose
isomers of glucose
 structure determines function…

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Cellulose
 Most abundant organic
compound on Earth
 Different glycosidic linkages creates linear
structure
herbivores have evolved a mechanism to
digest cellulose
 most carnivores have not

 that’s why they
eat meat to get
their energy &
nutrients
 cellulose = undigestible
roughage
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Digesting starch vs. cellulose
starch
easy to
digest
enzyme
cellulose
hard to
digest
enzyme
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only bacteria can digest
Helpful bacteria
 How can herbivores digest cellulose so well?

BACTERIA live in their digestive systems & help digest
cellulose-rich (grass) meals
Ruminants
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Tell
I eatme about
the rabbits,
WHAT!
again, George!
Chitin
Another important structural
polysaccharide
Is found in the exoskeleton of arthropods
Can be used as surgical thread


CH2O
H
O OH
H
H
OH H
OH
H
H
NH
C
O
CH3
(a) The structure of the (b) Chitin forms the exoskeleton
of arthropods. This cicada
chitin monomer.
is molting, shedding its old
exoskeleton and emerging
Figure 5.10 A–C
in adult form.
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(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.
17
BUILD
Let’s eat
some
X
Carbohydrates!
AP Biology