Macromolecules

The building blocks of life…

Macromolecules

Cells are composed of several types of biological macromolecules.

These function as energy-storage molecules, structural components, and in information storage, and are primarily composed of carbon, hydrogen and oxygen.

Carbohydrates

carbon, hydrogen & oxygen in a 1:2:1 ratio exist as monosaccharides, disaccharides

and polysaccharides among the most abundant molecules on

Earth

Monosaccharides

“single sugars” general formula is

(CH2O)n

glucose (top) and ribose (bottom) are monosaccharides

O

OH

HH

H

OH

OH

H OH

H

OH

O H

OHH

OH

H

OH

H

OH

Disaccharides

“double sugars” formed by dehydration synthesis from two

monosaccharides sucrose, maltose, and lactose are all

disaccharides

Synthesis of MaltoseO

OH

HH

H

OH

OH

H OH

H

OH

O

OH

HH

H

OH

OH

H OH

H

OH

O

OH

HH

H

OH

H OH

H

OH

O

O

HH

H

OH

OH

H OH

H

OH

-glucose - glucose

maltose

Polysaccharides

straight or branched chains of monosaccharides connected by glycosidic linkages

storage (e.g. starch, glycogen) or structural (e.g. cellulose, chitin)

Polysaccharide Structure

Proteins

proteins are chains of amino acids connected by peptide linkages

order of amino acids for a particular protein is determined by the gene which codes for it

Amino Acid Structure

all amino acids have the same basic structure

“R” group is different for each amino acid

NH2

H

R

O

OH

carboxyl group

amino group

Peptide Linkages

O

NH2

SH

N

O

OHH

O

NH2

SH OH

O

NH2OH

peptide linkage

cysteine glycine

Levels of Protein Structure

Primary the specific sequence

of amino acids coded by DNA

Secondary the folding or coiling

of the amino acid chain

caused by interactions between “R” groups

-Helix -Pleated Sheet

Tertiary the unique three-

dimensional shape of the protein

enzymes are globular proteins

collagen is a fibrous protein

Quaternary interactions between

separate polypeptide chains, or “subunits”

hemoglobin is composed of four subunits

Lipids lipids are a group of hydrophobic

molecules “neutral fats” are uncharged lipids

composed of glycerol and fatty acids fats are solid at room temperature oils are liquid at room temperature steroids and phospholipids are amphiphilic

Steroid Structure

steroids all have the same basic structure of four fused hydrocarbon rings

cholesterol is used to synthesize many other steroids in the body

CH3

OH

CH3

CH3

CH3

CH3

cholesterol

Phospholipid Structure

glycerol backbone has two fatty acids and one charged inorganic phosphate group attached

primary component of cell membranes

Triglycerides triglycerides are neutral fats glycerol is the “backbone” molecule fatty acids attach to glycerol by ester

linkages saturated fatty acids have no double

bonds between carbons unsaturated fatty acids have at least one

double bond between carbons

Triglyceride Synthesis

OH

OH

OH

CH3

O

OH

CH3

O

OH

CH3

O

OH

O

O

O

O

O

O

CH3

CH3

CH3

glycerol3 fatty acids

ester linkage

triglyceride

Nucleic Acids

Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA)

composed of nitrogen-containing “bases” attached to a backbone of alternating pentose sugars and inorganic phosphate

function in information storage (DNA) and transfer (RNA)

“Bases” of DNA & RNAPurines Pyrimidines

adenine thymine

guanine cytosine

uracil

N

NN

NH

NH2

N

NHN

NH

NH2

O

NH

NHCH3

O

O

NH

N

NH2

O

NH

NH

O

O

DNA deoxyribose sugar adenine, guanine, cytosine, thymine bases arranged in a double helix

RNA ribose sugar adenine, guanine, cytosine, uracil bases single-stranded

References MIT Biology Hypertextbook(1996)

http://esg-www.mit.edu:8001/esgbio/lm/sugars/sugars.html (3/9/2001)

Farabee, M.J., (2001) An Online Biology Book. Chemistry 2: Water and Organic Molecules http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookCHEM2.html (3/9/2002)

A.C.D. Labs (2002) ChemSketch (Freeware), available for download at http://www.acdlabs.com/. Used for molecular structure diagrams.