Ch. 5 - Macromolecules

Ch. 5 - 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 (polymerization)– monomers

• building blocks• repeated small units

– covalent bonds

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 enzymes

HydrolysisDigestion

enzyme

OH

OH

H

H

HO

CH2OH

HH

H

OH

O

Carbohydratesenergy

molecules

Carbohydrates• Carbohydrates are composed of C, H, O

carbo - hydr - ateCH2O

• Function:– energy – energy storage – structural materials

• Monomer: simple sugars= glucose, fructose, galactose

sugar sugar sugar sugar sugar sugar sugarsugar

C6H12O6(CH2O)x

Numbered carbons

C

CC

C

CC

1'

2'3'

4'

5'6'

O

energy stored in C-C bonds

Simple & complex sugars• Monosaccharides

– simple 1 monomer sugars– These link to form:

• Disaccharides– 2 monomers– sucrose

• Polysaccharides – large chains of monosaccharides– Starch, glycogen

OH

OH

H

H

HO

CH2OH

HH

H

OH

O

Glucose

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

– 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)

Polysaccharide diversity

• Molecular structure determines function

isomers of glucose structure determines function…

in starch in cellulose

Digesting starch vs. cellulose

starcheasy todigest enzyme

enzyme

cellulosehard todigest

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• Cell walls of plants!!

Chitin, a different structural polysaccharide

(a) The structure of the chitin monomer.

OCH2OH

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

Cowcan digest cellulose well, with the help of bacteria in gut, no need to eat other sugars

Gorillacan’t digest cellulose well; must add another sugar source, like fruit to diet

1. Which of the following is a polymer?A. Carbon atomsB. Simple sugar (aka monosaccharide)C. GlucoseD. CelluloseE. Deoxyribose

2. Starch and Glycogen both:I. Serve as energy storage for organismsII.Provide structure and supportIII. Are structural isomers of glucose

I onlyII onlyI and II onlyI and III onlyI, II, and III