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AP BiologyChapter 3: Structure and Function of Macromolecules
(Independently brush up on Ch 2 and Ch 3.1)
Macromolecules
Smaller organic molecules join together to form larger molecules macromolecules
4 major classes of macromolecules: carbohydrates lipids proteins nucleic acids
H2O
HO
HO H
H HHO
Polymers
Long molecules built by linking repeating building blocks in a chain monomers
building blocks repeated small units
covalent bonds
H2O
HO
HO H
H HHO
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
enzyme
Dehydration synthesis - Condensation reaction, in which the lost molecule = H2O
Dehydration synthesis - Condensation reaction, in which the lost molecule = H2O
Condensation reaction - two molecules join, lose a smaller one
Condensation reaction - two molecules join, lose a smaller one
Dehydration Synthesis
H2O
HO H
HO H HO H
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
HydrolysisHydrolysis
DigestionDigestion
enzyme
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?
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.
Carbohydrates
Carbohydrates
a.k.a. wheeee energy! :D
Carbohydrates Carbohydrates are composed of C, H,
Ocarbo - hydr - ate
CH2O)x C6H12O6
Function: energy energy storage raw materials structural materials
Monomer: sugars (monosaccharide)
sugar sugar sugar sugar sugar sugar sugarsugar
C6H12O6(CH2O)x
Sugars
Most names for sugars end in -ose Classified by number of carbons
6C = hexose (glucose) 5C = pentose (ribose) 3C = triose (glyceraldehyde)
6 5 3
Sugar structure
5C & 6C sugars form rings in solution
Numbered carbons
C
CC
C
CC
1'
2'3'
4'
5'
6'
O
energy stored in bondsenergy stored in bonds
You’ll see this come back in our DNA unit…
Simple & complex sugars Monosaccharides
simple 1 monomer sugars Ex: glucose
Disaccharides 2 monomers
Ex: sucrose
Polysaccharides 3+ monomers
Ex: starch, cellulose, glycogen
Building sugars Dehydration synthesis
|fructose
|glucose
monosaccharides
|sucrose
(table sugar)
disaccharide
H2O
Polysaccharides
Polymers of sugars 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)
Polysaccharide diversity Molecular structure determines function - a
major theme!
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!
in starch in cellulose
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
Helpful bacteria How can herbivores digest cellulose so well? BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals
Ruminants
Discussion In EXACTLY 20 words, summarize the most important point or points to remember about carbohydrates.
Lipids: Fats & Oils
Lipid Primary Function:
long term energy storageconcentrated energy
Lipids
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
Same as carbohydrates, but different structure = different
function!
Fats
Structure: glycerol (3C alcohol) + fatty acid
fatty acid = long HC “tail” with carboxyl (COOH) group “head”
dehydration synthesis
H2O
enzyme
Building Fats
Triacylglycerol 3 fatty acids linked to glycerol ester linkage between OH & COOH
hydroxyl carboxyl
Dehydration synthesis
dehydration synthesis
H2O
H2O
H2O
H2O
enzyme
enzyme
enzyme
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?
Why?
Fats store energy Long HC chain
polar or non-polar? hydrophilic or hydrophobic?
Functions: energy storage
2x carbohydrates cushion organs membranes & waterproofing insulates body
think whale blubber!
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?
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
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 doublebonded C prevent the molecules from packing tightly together
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)
Phospholipids Structure:
glycerol + 2 fatty acids + PO4
PO4 = negatively charged
Phospholipids Hydrophobic or hydrophilic?
fatty acid tails = PO4 head = split “personality”
interaction with H2O is complex & very important!
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
Why is this important?
Phospholipids create a barrier in water define outside vs. inside they make cell membranes!
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
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
Cholesterol
helps keep cell membranes fluid & flexible
Important component of cell membrane
From Cholesterol Sex Hormones What a big difference a few atoms can make!
Discussion In EXACTLY 20 words, summarize the most important point or points to remember about lipids.