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.