How To Make Biological Molecules
(Ch. 5)
Macromolecules
• Smaller organic molecules join together to
form larger molecules
– macromolecules
• 4 major classes of
macromolecules:
– carbohydrates
– lipids
– proteins
– nucleic acids
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
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
HO
H
How to break down a polymer
Breaking up
is hard to do!
• Digestion
– use H2O to breakdown polymers
• reverse of dehydration synthesis
• cleave off one monomer at a time
• H2O is split into H+ and OH–
– H+ & OH– attach to ends
– requires enzymes
– releases energy
HO
H2O
enzyme
H
Hydrolysis
Digestion
HO
H
HO
H
Any Questions??
2007-2008
CH2OH
H
O
H
OH
H
H
OH
HO
H
OH
Carbohydrates
energy
molecules
Carbohydrates
• Carbohydrates are composed of C, H, O
carbo - hydr - ate
CH2O
• Function:
(CH2O)x
– energy
C6H12O6
– energy storage
– raw materials
– structural materials
• Monomer: sugars
• ex: sugars, starches, cellulose
sugar sugar sugar sugar sugar sugar sugar sugar
Sugar structure
5C & 6C sugars form rings in solution
Where do
you find solutions
in biology?
In cells!
Carbons are numbered
Numbered carbons
C 6'
5' C
O
4' C
C1'
energy stored in C-C bonds
C3'
C2'
Simple & complex sugars
• Monosaccharides
– simple 1 monomer sugars
– glucose
• Disaccharides
– 2 monomers
– sucrose
• Polysaccharides
– large polymers
– starch
CH2OH
H
O
H
OH
H
H
OH
HO
Glucose
H
OH
Building sugars
• Dehydration synthesis
monosaccharides
|
glucose
H2O
|
glucose
disaccharide
|
maltose
glycosidic linkage
Building sugars
• Dehydration synthesis
monosaccharides
|
glucose
H2O
|
fructose
disaccharide
|
sucrose
(table sugar)
Polysaccharides
• Polymers of sugars
– costs little energy to build
– easily reversible = release energy
• Function:
– energy storage
• starch (plants)
• glycogen (animals)
– in liver & muscles
– structure
• cellulose (plants)
• chitin (arthropods & fungi)
Polymers of glucose units are used as temporary
food storage in both plant and animal cells.
Glucose units are connected to one another by
1, 4-linkages to make a linear polymer and by 1,
6-linkages to make branch points.
Numbered carbons
C 6'
5' C
O
4' C
C1'
C3'
C2'
Linear vs. branched polysaccharides
starch
(plant)
energy
storage
glycogen
(animal)
What does
branching do?
Digesting starch vs. cellulose
starch
easy to
digest
enzyme
cellulose
hard to
digest
enzyme
Cellulose
• Most abundant organic
compound on Earth
– 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
Chitin, a different structural
polysaccharide
H
OH
CH2OH
O OH
H
OH H
H
H
NH
C
O
CH3
(a) The structure of the
chitin monomer.
(b) Chitin forms the exoskeleton of arthropods. This
cicada is molting, shedding its
old exoskeleton and emerging
in adult form. It is also found in
Fungal Cell Walls.
(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.
Cow
can digest cellulose well;
no need to eat other sugars
Gorilla
can’t digest cellulose well; must
add another sugar source, like
fruit to diet
Helpful bacteria
• How can herbivores digest cellulose so well?
– BACTERIA live in their digestive systems & help digest celluloserich (grass) meals
Caprophage
Ruminants
Tell Ime
about
eat
the rabbits,
WHAT!
again,
George!
Review Questions
Which of the following is a polymer?
A. Simple sugar (aka monosaccharide)
B. Carbon atoms
C. Glucose
D. Cellulose
E. deoxyribose
Starch and Glycogen both
I. Serve as energy storage for
organisms
II. Provide structure and support
III. Are structural isomers of glucose
A. I only
B. II only
C. I and II only
D. I and III only
E. I, II, and III