1. Ch. 5 - Macromolecules
Smaller organic molecules join together to form larger molecules
macromolecules
4 major classes of macromolecules:
carbohydrates
lipids
proteins
nucleic acids

2. Dehydration synthesis
Polymers
Long molecules built by linking repeating building blocks in a chain (polymerization)
monomers
building blocks
repeated small units
covalent bonds
H2O HO H
• great variety of polymers can be built from a small set of monomers
• monomers can be connected in many combinations like the 26 letters in the alphabet can be used to create a great diversity of words
• each cell has millions of different macromolecules
Dehydration synthesis

3. 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 split into H+ and OH–
H+ & OH– attach to ends
requires enzymes
H2O HO H
enzyme
Most macromolecules are polymers
• build:
condensation (dehydration) reaction
• breakdown:
hydrolysis
An immense variety of polymers can be built from a small set of monomers
Hydrolysis
Digestion

4. OH H HO
CH2OH O
Carbohydrates
energy molecules

5. Carbohydrates are composed of C, H, O
Function:
energy
energy storage
structural materials
Monomer: simple sugars= glucose, fructose, galactose
(CH2O)x
C6H12O6
carb = carbon
hydr = hydrogen
ate = oxygen compound
sugar

6. energy stored in C-C bonds
Numbered carbons C 6' C O 5' C C 4' 1'
energy stored in C-C bonds C C 3' 2'

7. Simple & complex sugarsOH H HO
CH2OH O
Glucose
Monosaccharides
simple 1 monomer sugars
These link to form:
Disaccharides
2 monomers
sucrose
Polysaccharides
large chains of monosaccharides
Starch, glycogen

8. Building sugars Dehydration synthesis monosaccharides disaccharide |
H2O
maltose |
glucose |
glucose |
maltose
glycosidic linkage

9. Building sugars Dehydration synthesis monosaccharides disaccharide |
H2O |
glucose |
fructose |
sucrose
(table sugar)
sucrose = table sugar

10. Polysaccharides Polymers of sugars Function:
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)
Polysaccharides are polymers of hundreds to thousands of monosaccharides

11. Polysaccharide diversity
Molecular structure determines function
in starch
in cellulose
isomers of glucose
structure determines function…

12. Digesting starch vs. cellulose
enzyme
starch easy to digest
cellulose hard to digest
Starch = all the glycosidic linkage are on same side = molecule lies flat
Cellulose = cross linking between OH (H bonds) = rigid structure
enzyme

13. 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
Cell walls of plants!!
Cross-linking between polysaccharide chains:
= rigid & hard to digest
The digestion of cellulose governs the life strategy of herbivores.
Either you do it really well and you’re a cow or an elephant (spend a long time digesting a lot of food with a little help from some microbes & have to walk around slowly for a long time carrying a lot of food in your stomach)
Or you do it inefficiently and have to supplement your diet with simple sugars, like fruit and nectar, and you’re a gorilla.

14. Chitin, a different structural polysaccharide
CH2OH O H OH H OH H OH H H NH C O
CH3
(b) Chitin forms the exo- skeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging
in adult form. It is also found in Fungal Cell Walls.
(a) The structure of the
chitin monomer.
(c) Chitin is used to make a
strong and flexible surgical
thread that decomposes after
the wound or incision heals.

15. Cow
can digest cellulose well, with the help of bacteria in gut, no need to eat other sugars
Gorilla
can’t digest cellulose well; must add another sugar source, like fruit to diet
The digestion of cellulose governs the life strategy of herbivores.
Either you do it really well and you’re a cow or an elephant (spend a long time digesting a lot of food with a little help from some microbes & have to walk around slowly for a long time carrying a lot of food in your stomach)
Or you do it inefficiently and have to supplement your diet with simple sugars, like fruit and nectar, and you’re a gorilla.
APBioTOPICS/20Biochemistry/MoviesAP/Macromolecule-Lifewire.swf

16. 1. Which of the following is a polymer?
Carbon atoms
Simple sugar (aka monosaccharide)
Glucose
Cellulose
Deoxyribose
2. Starch and Glycogen both:
I. Serve as energy storage for organisms
II.Provide structure and support
III. Are structural isomers of glucose
I only
II only
I and II only
I and III only
I, II, and III