1. Chapter 5. Macromolecules

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

3. Polymers
Long molecules built by linking chain of repeating smaller units
polymers
monomers = repeated small units
covalent bonds
• 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

4. How to build a polymer Condensation reaction dehydration synthesis
joins monomers by “taking” H2O out
1 monomer provides OH
the other monomer provides H
together these form H2O
requires energy & enzymes

5. How to break down a polymer
Hydrolysis
use H2O to break apart monomers
reverse of condensation reaction
H2O is split into H and OH
H & OH group attach where the covalent bond used to be
ex: digestion is hydrolysis
Most macromolecules are polymers
• build:
condensation (dehydration) reaction
• breakdown:
hydrolysis
An immense variety of polymers can be built from a small set of monomers

6. Carbohydrates

7. So what’s all this talk about carbs?
Atkin’s Diet
South Beach Diet

8. Carbohydrates are composed of C, H, O carbo - hydr - ate
(CH2O)x C6H12O6
Function:
energy u energy storage
raw materials u structural materials
Monomer: sugars
ex: sugars & starches
carb = caron
hydr = hydrogen
ate = oxygen compound

9. Sugars Most names for sugars end in -ose
Classified by number of carbons
6C = hexose (glucose)
5C = pentose (fructose, ribose)
3C = triose (glyceraldehyde)

10. What functional groups?
carbonyl
aldehyde
ketone
hydroxyl

11. Sugar structure 5C & 6C sugars form rings in aqueous solutions
in cells!
Carbons are numbered

12. Numbered carbons C 6' C O 5' C C 4' 1' C C 3' 2'

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

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

15. Building sugars Dehydration synthesis monosaccharides disaccharide |
sucrose = table sugar |
glucose |
fructose |
sucrose
structural isomers
glycosidic linkage

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

17. Branched vs linear polysaccharides
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.

18. Polysaccharide diversity
Molecular structure determines function
isomers of glucose
How does structure influence function…

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

20. Cellulose Most abundant organic compound on Earth
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.

21. Glycemic index Which food will get into your blood more quickly? apple
rice cakes
corn flakes
bagel
peanut M&M

22. Glycemic index
Ranking of carbohydrates based on their immediate effect on blood glucose (blood sugar) levels
Carbohydrate foods that breakdown quickly during digestion have the highest glycemic indices. Their blood sugar response is fast & high.

23. Glycemic index Which food will get into your blood more quickly?
apple 36
rice cakes 82
corn flakes 84
bagel 72
peanut M&M 33
Why do we find sweet foods pleasurable to eat?
Why are we attracted to sweet food?

24. Let’s build some Carbohydrates!