1. Building Blocks of Life
Macromolecules
Building Blocks of Life

2. Smaller molecules join together to form MACROMOLECULES
4 types:
carbohydrates
proteins
nucleic acids
lipids

3. Dehydration synthesis
Polymers
Long molecules built by linking repeating building blocks called monomers
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

4. Building a Polymer Synthesis joins monomers by “taking” H2O out
one monomer donates OH–
other monomer donates H+
together form H2O
requires energy & enzymes
H2O HO H
enzyme
Dehydration synthesis
“Condensation reaction”

5. Breaking down a polymer
Digestion
use H2O
reverse of dehydration synthesis
breaks 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”

6. OH H HO
CH2OH O
Carbohydrates
energy molecules

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

8. 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

9. 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'

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

11. Building sugars Dehydration synthesis/condensation rxn monosaccharides
disaccharide
maltose |
glucose |
glucose |
maltose
glycosidic linkage

12. Building sugars Synthesis monosaccharides disaccharide | glucose |
fructose |
sucrose
(table sugar)
sucrose = table sugar

13. Polysaccharides Polymers of sugars Function:
costs little energy to build
easily reversible = release energy
Function:
energy storage
starch (plants)
glycogen (animals)
structure = building materials
cellulose (plants)
chitin (arthropods & fungi)
Polysaccharides are polymers of hundreds to thousands of monosaccharides

14. Linear vs. branched polysaccharides
starch
(plant)
(amylose)
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.
glycogen
(animal)

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

16. 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

17. Cellulose Most abundant organic compound on Earth
herbivores can digest cellulose
most carnivores cannot digest cellulose
that’s why they eat meat to get their energy & nutrients
cellulose = 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.

18. 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.
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19. Helpful bacteria How can cows digest cellulose?
bacteria live in their gut & help digest cellulose-rich (grass) meals