1. Chapter 5: Macromolecules

2. Macromolecules Large organic molecules built by smaller molecules.
4 major classes of macromolecules:
carbohydrates
lipids
proteins
nucleic acids

3. Dehydration synthesis
Polymers:
Long molecules built by linking repeating building blocks in a chain
Monomers are small building blocks
covalent bonds between
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

4. To build a polymer Take out water: called dehydration synthesis
or condensation reaction:
joins monomers by “taking” H2O out
one monomer loses OH–
other monomer loses H+
requires energy & enzymes
H2O HO H
enzyme
Dehydration synthesis
Condensation reaction

5. To break down a polymer Add H2O to breakdown polymers requires enzymes
reverse of dehydration synthesis
H2O is split into H+ and OH–
H+ & OH– attach to ends
requires enzymes
releases energy
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

6. Carbohydrates

7. Carbohydrates - composed of C, H, O Carb-o – hydrate Used for: energy
energy storage
raw materials
structural materials
Building blocks are sugars
carb = carbon
hydr = hydrogen
ate = oxygen compound
sugar

8. Sugar structure 5C & 6C sugars form rings in solution
Carbons are numbered

9. Carbons are numbered: C 6' C O 5' C C 4' 1' C C 3' 2'

10. Sugars: end in -ose Monosaccharides: glucose fructose
Disaccharides: glucose + fructose = sucrose
Others: maltose, lactose, dextrose

11. Simple & complex sugars
Monosaccharides
1 monomer
glucose
Disaccharides
2 monomers
sucrose
Polysaccharides
large polymers
starch

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

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

14. Polysaccharides Polymers of sugars Function: energy storage structure
starch (plants)
glycogen (animals)
Glucose stored in liver
structure
cellulose (plants)
chitin (arthropods & fungi)
Polysaccharides are polymers of hundreds to thousands of monosaccharides

15. Chitin: polysaccharide in lobster shells, insect bodies
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.

16. Linear vs. branched polysaccharides
slow release
starch
(plant)
energy storage
Can you see the difference between starch & glycogen?
Which is easier to digest?
Glycogen = many branches = many ends
Enzyme can digest at multiple ends. Animals use glycogen for energy storage == want rapid release.
Form follows function.
APBio/TOPICS/Biochemistry/MoviesAP/05_07Polysaccharides_A.swf
glycogen
(animal)
fast release

17. Polysaccharides Molecular structure determines function in starch
in cellulose
isomers of glucose
structure determines function…

18. 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
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.

19. 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

20. BACTERIA such as E. coli live in digestive systems & help digest cellulose-rich grass.