Chapter 5: Macromolecules

Macromolecules• Large organic molecules built by smaller

molecules.• 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 are small building blocks – covalent bonds between

Dehydration synthesis

H2O

HO

HO H

H HHO

To build a polymerTake out water: called dehydration synthesis or condensation reaction:

– joins monomers by “taking” H2O out• one monomer loses OH–

• other monomer loses H+

– requires energy & enzymes

enzymeDehydration synthesis

Condensation reaction

H2O

HO H

HO H HO H

To break down a polymerAdd H2O to breakdown polymers

• reverse of dehydration synthesis

• H2O is split into H+ and OH–

– H+ & OH– attach to ends

– requires enzymes– releases energy

Hydrolysis

Digestion

enzyme

Carbohydrates

Carbohydrates- composed of C, H, O

Carb-o – hydrateUsed for:

– energy – energy storage– raw materials – structural materials

– Building blocks are sugars

sugar sugar sugar sugar sugar sugar sugarsugar

Sugar structure5C & 6C sugars form rings in solution

Carbons are numbered

Carbons are numbered:

C

CC

C

CC

1'

2'3'

4'

5'

6'

O

Sugars: end in -ose

• Monosaccharides: glucose fructose• Disaccharides: glucose + fructose = sucrose

• Others: maltose, lactose, dextrose

Simple & complex sugars• Monosaccharides

1 monomer – glucose

• Disaccharides2 monomers– sucrose

• Polysaccharides – large polymers– starch

Building sugars• Dehydration synthesis

glycosidic linkage

|glucose

|glucose

monosaccharides disaccharide

|maltose

H2O

Building sugars• Dehydration synthesis

|fructose

|glucose

monosaccharides

|sucrose

(table sugar)

disaccharide

H2O

Polysaccharides • Polymers of sugars• Function:

– energy storage • starch (plants)• glycogen (animals)

Glucose stored in liver

– structure• cellulose (plants)• chitin (arthropods & fungi)

Chitin: polysaccharide in lobster shells, insect bodies

(a) The structure of the chitin monomer.

O

CH2OH

OHH

H OH

H

NH

C

CH3

O

H

H

(b) Chitin forms the exo- skeleton of arthropods. This

cicada is molting, shedding its old exoskeleton and emergingin adult form. It is also found in

Fungal Cell Walls.

(c) Chitin is used to make a strong and flexible surgical

thread that decomposes after the wound or incision heals.

OH

Linear vs. branched polysaccharides

starch(plant)

glycogen(animal)

energystorag

e

slow release

fast release

Polysaccharides

• Molecular structure determines function

isomers of glucose structure determines function…

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

Digesting starch vs. cellulose

starcheasy todigest enzyme

enzyme

cellulosehard todigest

– BACTERIA such as E. coli live in digestive systems & help digest cellulose-rich grass.