1

The Chemical Building Blocks of Life

Chapter 3

2

Outline

• Biological Molecules– Macromolecules

ProteinsStructure and Denaturation

Nucleic AcidsDNA and RNA

LipidsFats and Phospholipids

CarbohydratesTransport and Storage

3

Biological Molecules

• The framework of biological molecules consists of carbon bonded to other carbon molecules, or other types of atoms.

– Hydrocarbons consist of carbon and hydrogen.

Covalent bonds store considerable energy.

4

Biological Molecules

• Functional groups– specific groups of atoms

attached to carbon backbones

retain definite chemical properties

• Macromolecules.– proteins– nucleic acids– lipids– carbohydrates

Hydroxyl

Carbonyl

Carboxyl

Amino

Sulfhydryl

Phosphate

Methyl

Acetic acid

Functional Group

StructuralFormula

Example

Acetaldehyde

Alanine

-mercaptoethanol

Glycerol phosphate

Pyruvate

HS

P

O–

O

O

HC

H

H

OH

O

OHC

H

HN

CO

Ethanol

C

H

H

CH

H

H

OH

CH

H

HC

O

OH

H

CH3

OH

CCHO NH

CH

H

HHC

O

CHOH

H HS HC

H

CH

OH

HC

OH

H HOC

H

P

O

C

O

C

O

HHC

H

O–

O–

O–

O–

5

Macromolecules

• Macromolecules are often polymers.– long molecule built by linking together

small, similar subunits Dehydration synthesis removes OH and

H during synthesis of a new molecule. Hydrolysis breaks a covalent bond by

adding OH and H.

6

Carbohydrates

• Carbohydrates are loosely defined as molecules that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio.

– monosaccharides - simple sugars– disaccharides - two monosaccharides

joined by a covalent bond– polysaccharides - macromolecules made

of monosaccharide subunits isomers - alternative forms of the same

substance

7

H H HHH

OH OH

OHO

OH H

OHO

OH

HO

O

OH

OH H

HH

HO

H H

HH

OH

H

OH

OH

OH

H

H

HO

CH2OH

HH

H

OH

O

GalactoseFructoseGlucose

RiboseGlyceraldehyde

3-carbonsugar

5-carbon sugars

6-carbon sugars

Deoxyribose

HH

H

H

H

H

OH

OH

OC

C

C4

5

1

3 2

4

4

4

4

5

5

55

666

1

1

1

1

3

3

2

233

2

2

1

3

2

CH2OH CH2OH

CH2OH CH2OH

CH2OH

H

Sucrose

OH

HO

O

HO

OH

OH

O

O

Lactose

OH

OHHO

H

H H

HH

H

H

H

H

H

HH

H

OH

OH

OH

O

H

H

OH HOH

O

GalactoseGlucose

Glucose

Glucose

Glucose

Fructose

Maltose

CH2OH

HOOHH

H H H HH HH H

H

OH

O

O

OH

OHOH

OCH2OH

CH2OH CH2OH

CH2OH

CH2OHCH2OH

CH2OH

Starch: chain of -glucose subunits

HOOH

OH HHH H

H

O O O O O

HOOH

OH HHH

HH

H

O

Cellulose: chain of - glucose subunits

OH

OH HHH H

H OH

OH HH

H H

H OH

OH HHH H

H OH

OH HHH H

H

O

Plantcell wall

H H

H

OH

OHH

OH

OHO O O

O O

14

4 1

form of glucose

form of glucose

4 1

14

H OH

HO H OH

H HO

OO H

O

HOH

HOHH

H O

CH2OH CH2OH CH2OH CH2OH

CH2OHCH2OH

CH2OH

CH2OH

CH2OH

OHHHH

C O

H C OH

OH

H C OH

H

HO C H

C OH C OH

H

Fructose

H C OH

H C OH

H C OH

H

HO C H

H C OH

H

Glucose Galactose

Structuralisomer

Stereo-isomer

H C

C O

HO C H

H C OH

H C OH

H

HO C H

H C OH

H

8

Carbohydrate Transport and Storage

• Transport disaccharides– Humans transport glucose as a simple

monosaccharide.– Plants transform glucose into a

disaccharide transport form.• Storage polysaccharides

– plant polysaccharides formed from glucose - starches

most is amylopectin

9

Structural Carbohydrates

• Cellulose - plants– alpha form or beta form of ring

• Chitin - arthropods and fungi– modified form of cellulose

10

Amino Acids

• Contain an amino group (-NH2), a carboxyl group (-COOH) and a hydrogen atom, all bonded to a central carbon atom

– twenty common amino acids grouped into five classes based on side groups

nonpolar amino acids polar uncharged amino acids charged amino acids aromatic amino acids special-function amino acids

11

Alanine(Ala)

Leucine(Leu)

Isoleucine(Ile)

Phenylalanine(Phe)

Tryptophan(Trp)

Tyrosine(Tyr)

Glutamine(Gln)

Asparagine(Asn)

Threonine(Thr)

Serine(Ser)

Glycine(Gly)

Glutamicacid (Glu)

Asparticacid (Asp

Histidine(His)

Lysine(Lys)

Arginine(Arg)

Charged

Polar uncharged

Nonpolar

NONAROMATIC AROMATIC

Valine(Val)

CH3

C C

H O

CH

C C

H O

C C

H O

CH

C C

H O

H C

C C C C

H O

NHC

C C

H O

OH

H C OH

C C

H O

C C

H O

C

NH2

O

CH2

C C O–

H O

OH

C

C C

H O

O

H

C C

H O

C C

H O

CO

C C

H O

NH

C

C C

H O

C C

H O

C N

HC NH+

CH

H

C C

H O

CO

CH3 CH3

CH3 CH3CH3

CH3 CH2

CH2

CH2

CH2

CH2

CH2CH2

NH2

CH3

CH2

NH2

H3N+ H3N+ H3N+ H3N+ H3N+ H3N+O–O–O–O–O–

H3N+H3N+H3N+H3N+H3N+

O–

O–

O– O– O– O– O–

CH2

CH2CH2 CH2 CH2

CH2

CH2

CH2

CH2

CH2

CH2

NH2+

NH3+

O–

H O

H3N+ H3N+ H3N+ H3N+ H3N+ H3N+O–O–O–O–O–

Proline(Pro)

CH CNH2+ O

Methionine(Met)

CH2

C C O–

H O

CH2

S

CH3

Cysteine(Cys)

H3N+ C C O–

H O

SH

SPECIAL FUNCTION

CH2

CH2CH2

CH2H3N+

O–

12

Amino Acids

• Peptide bond links two amino acids.– A protein is composed of one or more long

chains of amino acids linked by peptide bonds (polypeptides).

13

Proteins

• Protein functions:– enzyme catalysis– defense– transport– support– motion– regulation– storage

14

Protein Structure

• Protein function is determined by its shape.– Protein structure

primary - specific amino acid sequence secondary - folding of amino acid chains motifs - folds or creases

supersecondary structure

15

Protein Structure

– tertiary - final folded shape of globular protein-determines protein activity and function

– domains - functional units

– quaternary - forms when two or more polypeptide chains associate to form a functional protein

16

CH2

CH3

CCC

O

O

NR

R

R

CNC C

C

H

C

H

H

C C S

CO

ON

N

C

H

H

CCSH

H

C

C O

ON

N

C

CCH3

Hydrogenbond

Disulfidebridge

Van der Waalsattraction

Hydrophobicexclusion

C

C

CC

C

O

(CH2)4

(NH3+)

CH2

O

ON

3

4

5

1

2

Ionic bondO–

CH3

CH3CH3

CH3

CH3CH3

CH3

N

Interactions that contribute to protein’s shape

17

Chaperone Proteins

• Chaperone proteins are special proteins which help new proteins fold correctly.

– Chaperone deficiencies may play a role in facilitating certain diseases.

18

Unfolding Proteins

• Denaturation refers to the process of changing a protein’s shape.

– usually rendered biologically inactive salt-curing and pickling used to preserve

food

19

Nucleic Acids

• Deoxyribonucleic Acid (DNA)– Encodes information used to assemble

proteins.• Ribonucleic Acid (RNA)

– Reads DNA-encoded information to direct protein synthesis.

20

Nucleic Acid Structure

• Nucleic acids are composed of long polymers of repeating subunits, nucleotides.

– five-carbon sugar– phosphate– nitrogenous base

purines adenine and guanine

pyrimidines cytosine, thymine,

and uracil

Phosphate group

Sugar

Nitrogenous base

N

N

O

4’

5’

1’

3’ 2’

28

7 6

394

5

P CH2

O

–O

O–

OH ROH in RNA

H in DNA

O

N

NH2

N1

21

The nitrogenous bases

Adenine

Guanine

CC

NN

N

C

HN

C

CH

O

H

Cytosine(both DNAand RNA)

Thymine(DNA only)

Uracil(RNA only)

HCC

NC

H

N

C

NH2

N

NCH

OCC

NC

H

N

CH

H

OCC

NC

H

N

C

O

HH3C

H

OCC

NC

H

N

C

O

HH

H

PURINES

PYRI

MIDINES

NH2

NH2

22

Nucleic Acid Structure

• DNA exists as double-stranded molecules.

– double helix– complementary base

pairing hydrogen bonding

• RNA exists as a single stand.

– contains ribose instead of deoxyribose

– contains uracil in place of thymine

5’

3’

P

P

P

P

OH

5-carbonsugar

Nitrogenous base

Phosphate group

O

O

O

O

Phosphodiesterbonds

23

Lipids

• Lipids are loosely defined as groups of molecules that are insoluble in water.

– fats and oils• Phospholipids form the core of all biological

membranes.– composed of three subunits

glycerol fatty acid phosphate group

Schematic Formula Space-filling model Icon

Polarhydrophilic

heads

Nonpolarhydro-phobic

tails

CH2

CO O

OO

OPO

O O–

H2C CH

C

CH3

Choline

Phosphate

Glycerol

Fatty

acid

Fatty

acid

CH2

CH2

CH3

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CHCHCH2

CH2

CH2

CH2

CH2

CH2

CH2

N+(CH3)3

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

24

Fats and Other Lipids

• Fats consist a of glycerol molecule with three attached fatty acids (triglyceride / triglycerol).

– Saturated fats - all internal carbon atoms are bonded to at least two hydrogen atoms

– Unsaturated fats - at least one double bond between successive carbon atoms

Polyunsaturated - contains more than one double bond

usually liquid at room temperature

25

To make a triglyceride

26

Saturated fat

Unsaturated fat

O

C

H

C

H

H

C

H

H

C

H

H

CH C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

O

O

C

H

CH

H

CH

H

CH

H

CH CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

O

O

C

H

C

H

H

C

H

H

C

H

H

CH C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

H

CH

H

CH

H

H

C

H

H

C

H

HO

H H

C

H

H

C

H

H

O

C

H

CH C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

C

H

H

C

H

C C

H H H

H

C

H

C C

H

O

H

C

H

CH

H

CH

H

O

C

H

CH CH

H

CH

H

CH

H

CH

H

CH

H

CH

H

CH

CH

H

C

H H

CH

CH

H

C

H H

CHH

CH H

O

HH

C

H

C

H

H

C

H

H

O

C

H

CH C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

C

H

H

C

H

C

H

C

H

H

C

H

C

H

C

H H

O

H

H

H

H

27

Fats as Energy Storage Molecules

• Fats, on average, yield about 9 kcal per gram versus 4 kcal per gram for carbohydrates.

– Animal fats are saturated while most plant fats are unsaturated.

Consumption of excess carbohydrates leads to conversion into starch, glycogen, or fats for future use.

28

Summary

• Biological Molecules– Macromolecules

CarbohydratesTransport and Storage

ProteinsStructure and Denaturation

Nucleic AcidsDNA and RNA

LipidsFats and Phospholipids

29