1. AP Biology Chapter 3: Structure and Function of Macromolecules (Independently brush up on Ch 2 and Ch 3.1)

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 repeating building blocks in a chain
monomers
building blocks
repeated small units
covalent bonds
H2O HO H

4. How to build a polymer 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
Condensation reaction - two molecules join, lose a smaller one
Dehydration synthesis - Condensation reaction, in which the lost molecule = H2O

5. Dehydration Synthesis

6. 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 hydrolytic enzymes
releases energy
H2O HO H
enzyme
Hydrolysis
Digestion

7. Discussion
Under what circumstances would you expect to find a cell conducting a great deal of dehydration synthesis?
In which organs or under what circumstances would you expect to find body cells conducting hydrolysis?

8. Variety of Polymers
Every cell has thousands of varieties of macromolecules
These molecules are constructed from only 40 to 50 common monomers
Analogy: 26 letters of the alphabet can be combined to form millions of words
Shortcoming: macromolecules are much longer than the average word and they can be branched or 3D.

9. Carbohydrates

10. Carbohydrates
a.k.a. wheeee energy! :D

11. Carbohydrates are composed of C, H, O
CH2O)x C6H12O6
Function:
energy u energy storage
raw materials u structural materials
Monomer: sugars (monosaccharide)
(CH2O)x
C6H12O6
sugar

12. 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) 6 5 3

13. Sugar structure
5C & 6C sugars form rings in solution

14. You’ll see this come back in our DNA unit…
Numbered carbons
You’ll see this come back in our DNA unit… C 6' C O 5' C C 4' 1'
energy stored in bonds C C 3' 2'

15. Simple & complex sugars
Monosaccharides
simple 1 monomer sugars
Ex: glucose
Disaccharides
2 monomers
Ex: sucrose
Polysaccharides
3+ monomers
Ex: starch, cellulose, glycogen

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

17. Polysaccharides Polymers of sugars Functions:
costs little energy to build
easily reversible = release energy
Functions:
energy storage
starch (plants)
glycogen (animals)
in liver & muscles
structure
cellulose (plants)
chitin (arthropods & fungi)

18. Polysaccharide diversity
Molecular structure determines function - a major theme!
in starch
in cellulose
Isomers of glucose
Different structure = connect to the next monomer in the chain differently = different 3D structure.
Starch - helical. Cellulose - straight, with free OH to bond to neighboring celluloses = rigid structure!

19. 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.

20. Helpful bacteria How can herbivores digest cellulose so well?
BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals
Ruminants

21. Discussion
In EXACTLY 20 words, summarize the most important point or points to remember about carbohydrates.

22. Lipids: Fats & Oils

23. Lipid Primary Function:
long term energy storage
concentrated energy

24. Lipids Lipids are composed of C, H, O “Family groups”
Same as carbohydrates, but different structure = different function!
Lipids are composed of C, H, O
long hydrocarbon chains (H-C)
“Family groups”
fats
phospholipids
steroids
Do not form polymers
big molecules made of smaller subunits
not a continuing chain

25. dehydration synthesis
Fats
Structure:
glycerol (3C alcohol) + fatty acid
fatty acid = long HC “tail” with carboxyl (COOH) group “head”
enzyme
H2O
dehydration synthesis

26. Building Fats Triacylglycerol 3 fatty acids linked to glycerol
ester linkage between OH & COOH
hydroxyl
carboxyl
BIG FAT molecule!!

27. Dehydration synthesis
H2O
dehydration synthesis
enzyme
H2O
Pulling the water out to free up the bond
enzyme
H2O
enzyme
H2O

28. Discussion
What kind of molecule would you expect to be hydrophobic - polar or non-polar?
Why?
Do you think lipids (such as fats, oils, waxes) are probably polar or non-polar?

29. Fats store energy Long HC chain Functions: polar or non-polar?
hydrophilic or hydrophobic?
Functions:
energy storage
2x carbohydrates
cushion organs
membranes &
waterproofing
insulates body
think whale blubber!

30. Discussion
Show me a human who doesn’t want to eat this and I’ll show you a LIAR.
Knowing their major functions, hypothesize: what occurred in evolutionary history that led to humans enjoying the tastes of fatty and sugary foods?

31. Structure & Function Saturated Fats All C bonded to H
No C=C double bonds
long, straight chain
most animal fats
solid at room temp.
contributes to cardiovascular disease (atherosclerosis) = plaque deposits
Mostly animal fats

32. Structure & Function Unsaturated Fats
C=C double bonds in the fatty acids
plant & fish fats
vegetable oils
liquid at room temperature
the kinks made by double bonded C prevent the molecules from packing tightly together
Mostly plant lipids
Think about “natural” peanut butter:
Lots of unsaturated fats Oil separates out
Companies want to make their product easier to use:
Stop the oil from separating Keep oil solid at room temp.
Hydrogenate it = chemically alter to saturate it
Affect nutrition?

33. Discussion
Unsaturated fats are widely considered to be healthier (sometimes called “good fats” for short) than saturated fats.
Why might this be? (Hint: think of their structures, and what they might mean for how easily the body would use them for energy vs. storing them in fat cells)

34. Phospholipids Structure: glycerol + 2 fatty acids + PO4
PO4 = negatively charged

35. Phospholipids Hydrophobic or hydrophilic? fatty acid tails =
PO4 head =
split “personality”
interaction with H2O is complex & very important!

36. Phospholipids in water
heads H2O
tails H2O
can self-assemble into “bubbles” called micelles
can also form a phospholipid bilayer
Early Earth history - a cell part that self-assembles!
bilayer

37. Why is this important? Phospholipids create a barrier in water
define outside vs. inside
they make cell membranes!

38. Steroids Structure: 4 fused C rings + ??
different steroids created by attaching different functional groups to rings
different structure creates different function
examples: cholesterol, sex hormones
cholesterol

39. Cholesterol Important cell component animal cell membranes
precursor of all other steroids
including vertebrate sex hormones
high levels in blood may contribute to cardiovascular disease

40. Cholesterol Important component of cell membrane
helps keep cell membranes fluid & flexible

41. From Cholesterol  Sex Hormones
What a big difference a few atoms can make!
Same C skeleton, different functional groups

42. Discussion
In EXACTLY 20 words, summarize the most important point or points to remember about lipids.