1. Building Blocks of Life
Chapter 5
Macromolecules
Building Blocks of Life

2. Chapter 5 Objectives:
Explain how polymers are synthesized (dehydration/condensation reaction) and broken down (hydrolysis/digestion reaction)
Describe the structure and function of the 4 major classes of macromolecules
Explain how the structure and sequence of monomers affects the function of the polymer.

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

4. Dehydration synthesis
Polymers
Long molecules built by linking repeating building blocks in a chain
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

5. You gotta be open to “bonding!
How to build a polymer
You gotta be open to “bonding!
Synthesis
joins monomers by “taking” H2O out
one monomer donates OH–
other monomer donates H+
together these form H2O
requires energy & enzymes
H2O HO H
enzyme
Dehydration synthesis
Condensation reaction

6. 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
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

7. Carbohydrates

8. OH H HO
CH2OH O
Carbohydrates
energy molecules

9. Carbohydrates are composed of C, H, O
(CH2O)x C6H12O6
Function:
energy u energy storage
raw materials u structural materials
Monomer: sugars
ex: sugars, starches, cellulose
(CH2O)x
C6H12O6
carb = carbon
hydr = hydrogen
ate = oxygen compound
sugar

10. Sugars 6 5 3 Most names for sugars end in -ose
Classified by number of carbons
6C = hexose (glucose)
5C = pentose (ribose)
3C = triose (glyceraldehyde)
Glyceraldehyde H OH O C OH H HO
CH2OH O
Glucose H OH HO O
Ribose
CH2OH 6 5 3

11. Functional groups determine function
carbonyl
aldehyde
carbonyl
ketone

12. Where do you find solutions in biology?
Sugar structure
5C & 6C sugars form rings in solution
Where do you find solutions in biology?
In cells!
Carbons are numbered

13. 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'

14. Simple & complex sugarsOH H HO
CH2OH O
Glucose
Simple & complex sugars
Monosaccharides
simple 1 monomer sugars
glucose
Disaccharides
2 monomers
sucrose
Polysaccharides
large polymers
starch

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

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

17. 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

18. Linear vs. branched polysaccharides
slow release
starch
(plant)
What does branching do?
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

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

20. 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

21. But it tastes like hay! Who can live on this stuff?!
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.
But it tastes like hay! Who can live on this stuff?!

22. Cow Gorilla can digest cellulose well; no need to eat other sugars
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

23. Tell me about the rabbits, again, George!
Helpful bacteria
How can herbivores digest cellulose so well?
BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals
Caprophage
I eat WHAT!
Tell me about the rabbits, again, George!
Ruminants

24. Let’s build some Carbohydrates!
EAT X
Let’s build some
Carbohydrates!