1. You are what you eat! Chapter 5
Macromolecules
You are what you eat!
Chapter 5

2. Carbohydrates Structure / monomer Function Examples monosaccharide
energy
raw materials
energy storage
structural compounds
Examples
glucose, starch, cellulose, glycogen
glycosidic bond

3. 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

4. C C O C C C C Numbered carbons
These will become important! 6' C O 5' C C 4' 1'
energy stored in C-C bonds harvested in cellular respiration C C 3' 2'

5. 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

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

7. 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

8. 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

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

10. 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.

11. 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.

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

13. Proteins Most structurally & functionally diverse group
Function: involved in almost everything
enzymes (pepsin, DNA polymerase)
structure (keratin, collagen)
carriers & transport (hemoglobin, aquaporin)
cell communication
signals (insulin & other hormones)
receptors
defense (antibodies)
movement (actin & myosin)
storage (bean seed proteins)
Storage: beans (seed proteins)
Movement: muscle fibers
Cell surface proteins: labels that ID cell as self vs. foreign
Antibodies: recognize the labels
ENZYMES!!!!

14. Proteins Structure monomer = amino acids polymer = polypeptide
H2O
Structure
monomer = amino acids
20 different amino acids
polymer = polypeptide
protein can be one or more polypeptide chains folded & bonded together
large & complex molecules
complex 3-D shape
Rubisco = 16 polypeptide chains
Hemoglobin = 4 polypeptide chains (2 alpha, 2 beta)
hemoglobin
Rubisco
growth hormones

15. Amino acids H O | H || —C— C—OH —N— R Structure central carbon
amino group
carboxyl group (acid)
R group (side chain)
variable group
different for each amino acid
confers unique chemical properties to each amino acid
like 20 different letters of an alphabet
can make many words (proteins)
—N— H R

16. Sulfur containing amino acids
Form disulfide bridges
covalent cross links betweens sulfhydryls
stabilizes 3-D structure
H-S – S-H

17. dehydration synthesis
Building proteins
Peptide bonds
covalent bond between NH2 (amine) of one amino acid & COOH (carboxyl) of another
C–N bond
H2O
dehydration synthesis
free COOH group on one end is ready to form another peptide bond so they “grow” in one direction from N-terminal to C-terminal
peptide bond

18. Building proteins Polypeptide chains have direction
N-terminus = NH2 end
C-terminus = COOH end
repeated sequence (N-C-C) is the polypeptide backbone
can only grow in one direction

19. Protein structure & function
Function depends on structure
3-D structure
twisted, folded, coiled into unique shape
Hemoglobin
Hemoglobin is the protein that makes blood red. It is composed of four protein chains, two alpha chains and two beta chains, each with a ring-like heme group containing an iron atom. Oxygen binds reversibly to these iron atoms and is transported through blood.
Pepsin
Pepsin is the first in a series of enzymes in our digestive system that digest proteins. In the stomach, protein chains bind in the deep active site groove of pepsin, seen in the upper illustration (from PDB entry 5pep), and are broken into smaller pieces. Then, a variety of proteases and peptidases in the intestine finish the job. The small fragments--amino acids and dipeptides--are then absorbed by cells for use as metabolic fuel or construction of new proteins.
Collagen– Your Most Plentiful Protein
About one quarter of all of the protein in your body is collagen. Collagen is a major structural protein, forming molecular cables that strengthen the tendons and vast, resilient sheets that support the skin and internal organs. Bones and teeth are made by adding mineral crystals to collagen. Collagen provides structure to our bodies, protecting and supporting the softer tissues and connecting them with the skeleton. But, in spite of its critical function in the body, collagen is a relatively simple protein.
pepsin
hemoglobin
collagen

20. Protein structure 3° 1° 4° 2° R groups hydrophobic interactions
disulfide bridges
(H & ionic bonds) 3°
multiple polypeptides
hydrophobic interactions 1°
sequence determines structure and…
structure determines function.
Change the sequence & that changes the structure which changes the function.
amino acid sequence
peptide bonds 4° 2°
determined by DNA
R groups
H bonds

21. Protein denaturation Unfolding a protein
conditions that disrupt H bonds, ionic bonds, disulfide bridges
temperature pH
salinity
alter 2° & 3° structure
alter 3-D shape
destroys functionality
some proteins can return to their functional shape after denaturation, many cannot

22. Nucleic Acids Function: genetic material stores information
genes
blueprint for building proteins
DNA  RNA  proteins
transfers information
blueprint for new cells
blueprint for next generation
DNA
proteins

23. Nucleic Acids Examples: Structure: RNA (ribonucleic acid)
single helix
DNA (deoxyribonucleic acid)
double helix
Structure:
monomers = nucleotides
DNA
RNA

24. Nucleotides 3 parts nitrogen base (C-N ring) pentose sugar (5C)
ribose in RNA
deoxyribose in DNA
phosphate (PO4) group
DNA & RNA are negatively charged:
Don’t cross membranes.
Contain DNA within nucleus
Need help transporting mRNA across nuclear envelope.
Also use this property in gel electrophoresis.

25. Lipids Lipids are composed of C, H, O “Family groups”
long hydrocarbon chains (H-C)
“Family groups”
fats
phospholipids
steroids
Do not form polymers
big molecules made of smaller subunits
not a continuing chain
Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties

26. dehydration synthesis
Fats
Structure:
glycerol (3C alcohol) + fatty acid
fatty acid = long HC “tail” with carboxyl (COOH) group “head”
enzyme
Look at structure… What makes them hydrophobic?
Note functional group = carboxyl
H2O
dehydration synthesis

27. Fats store energy Long HC chain Function: polar or non-polar?
hydrophilic or hydrophobic?
Function:
energy storage
concentrated
all H-C!
2x carbohydrates
cushion organs
insulates body
think whale blubber!
What happens when you add oil to water
Why is there a lot of energy stored in fats?
• big molecule
• lots of bonds of stored energy
So why are we attracted to eating fat?
Think about our ancestors on the Serengeti Plain & during the Ice Age. Was eating fat an advantage?

28. 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

29. 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?

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

31. Phospholipids in water
Hydrophilic heads “attracted” to H2O
Hydrophobic tails “hide” from H2O
can self-assemble into “bubbles”
bubble = “micelle”
can also form a phospholipid bilayer
early evolutionary stage of cell?
water
bilayer
water

32. 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

33. 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

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