AP Biology

Macromolecules

You are what you eat!

Chapter 5

AP Biology

Organic Compounds § Contain bonds between CARBON

glycosidic bond

AP Biology

Carbohydrates § Structure / monomer

u monosaccharide §  Function

u energy u  raw materials u energy storage u structural compounds

§ Examples u glucose, starch, cellulose, glycogen

glycosidic bond

AP Biology

Sugars § Most names for sugars end in -ose § Classified by number of carbons

u 6C = hexose (glucose) u 5C = pentose (ribose) u 3C = triose (glyceraldehyde)

OH

OH

H

H

HO

CH2OH

H H

H

OH

O

Glucose

H

OH

HO

O H

H HO

H

Ribose

CH2OH

Glyceraldehyde

H

H

H

H

OH

OH

O C

C

C 6 5 3

AP Biology

Numbered carbons

C

C C

C

C

C

1'

2' 3'

4'

5' 6'

O

energy stored in C-C bonds harvested in cellular respiration

AP Biology

Simple & complex sugars § Monosaccharides

u simple 1 monomer sugars u glucose

§ Disaccharides u 2 monomers u sucrose

§ Polysaccharides u  large polymers u starch

OH

OH

H

H

HO

CH2OH

H H

H

OH

O

Glucose

AP Biology

Building sugars § Dehydration synthesis

| fructose

| glucose

monosaccharides

| sucrose

(table sugar)

disaccharide

H2O

AP Biology

Polysaccharides § Polymers of sugars

u costs little energy to build u easily reversible = release energy

§  Function: u energy storage

§  starch (plants) §  glycogen (animals)

w  in liver & muscles

u structure §  cellulose (plants) §  chitin (arthropods & fungi)

AP Biology

Linear vs. branched polysaccharides

starch (plant)

glycogen (animal)

energy storage

What does branching do?

Faster digestion!

slow release

fast release

AP Biology

Polysaccharide diversity § Molecular structure determines function

u  isomers of glucose u structure determines function…

in starch in cellulose

AP Biology

Cellulose § Most abundant organic

compound on Earth u herbivores have evolved a mechanism to

digest cellulose u most carnivores have not:

§  that’s why they eat meat to get their energy & nutrients

§  cellulose = undigestible roughage

But it tastes like hay!

Who can live on this stuff?!

Regents Biology

Helpful bacteria §  How can herbivores digest cellulose so well?

u  BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals

Ruminants

Tell me about the rabbits,

again, George!

I eat WHAT!

Caprophage

Regents Biology

Proteins § Structure

u monomer = amino acids §  20 different amino acids

u polymer = polypeptide §  protein can be one or more polypeptide

chains folded & bonded together §  large & complex molecules §  complex 3-D shape

Rubisco

hemoglobin

growth hormones

H2O

Regents Biology

Proteins § Most structurally & functionally diverse group §  Function: involved in almost everything

u  enzymes (pepsin, lactase, DNA polymerase) u  structure (keratin, collagen) u  carriers & transport (hemoglobin, aquaporin) u  cell communication

§  signals (insulin & other hormones) §  receptors

u  defense (antibodies) u  movement (actin & myosin) u  storage (bean seed proteins)

Regents Biology

Amino acids § Structure

u central carbon u amino group u carboxyl group (acid) u R group (side chain)

§  variable group §  different for each amino acid §  confers unique chemical

properties to each amino acid w  like 20 different letters of an

alphabet w can make many words (proteins)

—N— H

H

C—OH || O

R

|

—C— |

H

Oh, I get it! amino = NH2 acid = COOH

Regents Biology

Building proteins § Peptide bonds

u covalent bond between NH2 (amine) of one amino acid & COOH (carboxyl) of another

u C–N bond

peptide bond

dehydration synthesis H2O

Regents Biology

Building proteins § Polypeptide chains have direction

u N-terminus = NH2 end u C-terminus = COOH end u  repeated sequence (N-C-C) is the

polypeptide backbone §  can only grow in one direction

Regents Biology

Protein structure & function

hemoglobin

§ Function depends on structure u 3-D structure

§  twisted, folded, coiled into unique shape

collagen

pepsin

Regents Biology

Protein structure

amino acid sequence

peptide bonds

1°

determined by DNA R groups

H bonds

R groups hydrophobic interactions

disulfide bridges (H & ionic bonds)

3° multiple

polypeptides hydrophobic interactions

4°

2°

Regents Biology

Sulfur containing amino acids §  Cysteine, Methionine §  Form disulfide bridges

u  covalent cross links betweens sulfhydryls u  stabilizes 3-D structure

You wondered why perms smell like

rotten eggs?

H-S – S-H

Regents Biology

Protein denaturation § Unfolding a protein

u conditions that disrupt H bonds, ionic bonds, disulfide bridges… §  temperature §  pH §  salinity

u alter 2° & 3° structure §  thus, altering 3-D shape

u destroys functionality §  some proteins can return to their functional shape

after denaturation, many cannot

In Biology, size doesn’t matter,

SHAPE matters!

Regents Biology proteins

DNA

Nucleic Acids § Function:

u genetic material § stores information

w genes w blueprint for building proteins

n  DNA → RNA → proteins § transfers information

w blueprint for new cells w blueprint for next generation

Regents Biology

Nucleic Acids § Examples:

u RNA (ribonucleic acid) §  single helix

u DNA (deoxyribonucleic acid) §  double helix

§ Structure: u monomers = nucleotides

RNA DNA

Regents Biology

Nucleotides §  3 parts

u nitrogen base (C-N ring) u pentose sugar (5C)

§  ribose in RNA §  deoxyribose in DNA

u phosphate (PO4) group

Are nucleic acids charged molecules?

Nitrogen base I’m the

A,T,C,G or U part!

Regents Biology

Lipids §  Lipids are composed of C, H, O

u  long hydrocarbon chains (H-C) §  “Family groups”

u  fats u phospholipids u steroids

§ Do not form polymers u big molecules made of smaller subunits u not a continuing chain

Regents Biology

Fats § Structure:

u glycerol (3C alcohol) + fatty acid §  fatty acid =

long HC “tail” with carboxyl (COOH) group “head”

dehydration synthesis

H2O

enzyme

Regents Biology

Fats store energy §  Long hydrocarbon chain

u polar or non-polar? u hydrophilic or hydrophobic?

§  Function: u energy storage

§  concentrated w all H-C!

§  2x carbohydrates u cushion organs u  insulates body

§  think whale blubber!

Why do humans like fatty foods?

Regents Biology

Saturated fats § All C bonded to H § No C=C double bonds

u  long, straight chain u most animal fats u solid at room temp.

§  contributes to cardiovascular disease (atherosclerosis) = plaque deposits

Regents Biology

Unsaturated fats § C=C double bonds in

the fatty acids u plant & fish fats u vegetable oils u  liquid at room temperature

§  the kinks made by double bonded C prevent the molecules from packing tightly together

mono-unsaturated? poly-unsaturated?

Regents Biology

Phospholipids § Structure:

u glycerol + 2 fatty acids + PO4

§ PO4 = negatively charged (which means the head molecule is…)

It’s just like a penguin…

A head at one end & a tail

at the other!

Regents Biology

Phospholipids in water § Hydrophilic heads “attracted” to H2O § Hydrophobic tails “hide” from H2O

u can self-assemble into “bubbles” §  bubble = “micelle” §  can also form a phospholipid bilayer §  early evolutionary stage of cell?

bilayer

water

water

Regents Biology

Steroids § Structure:

u 4 fused C rings + ?? §  different steroids created by attaching different

functional groups to rings §  different structure creates different function

u examples: cholesterol, sex hormones

cholesterol

Regents Biology

Cholesterol §  Important cell component

u animal cell membranes u precursor of all other steroids

§  including vertebrate sex hormones u high levels in blood may contribute to

cardiovascular disease

Regents Biology

From Cholesterol → Sex Hormones § What a big difference a few atoms can make!