Chapter 3 – Biological Molecules

• 3.1 Why is Carbon So Important in Biological Molecules?

• 3.2 How Are Organic Molecules Synthesized?

• 3.3 What Are Carbohydrates?

• 3.4 What Are Lipids?

• 3.5 What Are Proteins?

• 3.6 What Are Nucleic Acids?

3.1 Why Is Carbon So Important in Biological Molecules?

• Organic molecules have a carbon skeleton with hydrogen

• Inorganic molecules do not have carbon (except CO2)

• Organic molecules have functional groups that determine their reactivity

3.2 How Are Organic Molecules Synthesized?

• Monomers (“one part”) are subunits (like Legos)

• Polymers (“many parts”) are made up of monomers, often long chains of monomers

OHH

OHO OH HO OHOH HO

Dehydration synthesis(dry out the molecule)

Molecules are broken apart by removing water

OHH

OOHHO HO OH HO OH

Hydrolysis (“cut water”)

Molecules are joined together by adding water

3.3 What Are Carbohydrates?

• Carbohydrates are made of carbon, hydrogen & oxygen in approximately 1:2:1 ratio

• Energy sources

• Most are soluble in water

• Monosaccharides are “one sugar”• Disaccharides are “two sugars”• Polysaccarides are “many sugars”

galactose

HO OHHOCH2

CH2OH

HO

HO

fructose

OH

H

H

H

H

H

H

CH2OH

H

OH

O

H HO

O

Carbohydrates usually have the approximate chemical formula of (CH2O)n

ribosein RNA

deoxyribosein DNA

H

HOCH2

H

OHOH

H H

H

HOCH2

H

OH

H H

H

OHOH OO

Glucose most common monosaccharideC6H12O6

glucose

2356 4 1

5

6

4

3 2

1

H

H

CH2OH

HO

OH

OH

O

H H

OH H

H

O OOOO

H H H

H

O

CCCCCCH

H

H

H H

H

H

OC

C

C

C

O

H

HH

H H

H

H

H O

O

C

C H

H

H

=

=

H

O O

OHH

O

glucose fructose sucrose

HO

OHOCH2

OH

HO

CH2OH

H H

OH

H OH

H

H

O HO

OCH2OH

H H

OH

H OH

H

HH

H

H

HOCH2 OHH

HOCH2H

H

H

HOCH2OH

O

OH

Dehydrationsynthesis

O

Common disaccharides• sucrose• lactose – milk sugar• maltose – malt sugar

3.3 What Are Carbohydrates?• Main types of polysaccharides:

– Starch is an energy-storage polysaccharide made of glucose subunits (plants)

– Glycogen like starch but for animals

– Cellulose structure and function. Cell walls in plants. Most things can’t digest it. (Roughage or fiber)

– Chitin: structure - exoskeletons of insects, crabs and spiders. Also cell walls of some fungi.

H

CH2OH

O

HO

H

OH H

OH

CH2OHO

HO

H

OH H

OH

CH2

O

HO

H

OH H

OH

CH2OH

OH

H

OH H

OH

CH2OH

OH

H

OH H

OH

O

CH2OH

OH

O

H

OH H

OH

H H H H

H H HH

O

H HH

masses ofstarch globules

100 micrometers

O

bundle ofcellulosemolecules

1 micrometer 1 micrometer

wood is mostly cellulose plant cell with cell wall close-up of cell wall

cellulose fiberindividual cellulosemolecules

CH2OH

O

OH H

HH

O

HH OH

H

CH2OH CH2OH

CH2OH

O

O

O

O

O

O

OH

OH OH

OH

OHH

H

H

HH H

H

H

HH H

H

H

H H

OH

CH2OH

H

CH3

H N H

H

H N H

OO

H

O

N H

O

O

O

H

OH OH HH H OH

H

H

H H

HO

N H

CH3

H

OH H

OH H

HO

H

CH2OH

CH2OH

O CO C

O C O C

CH3

CH3

CH2OH

Chitin

3.4 What Are Lipids?• Contain almost all carbon and hydrogen

• Hydrophobic and insoluble in water

• Energy storage, waterproof covering, cell membranes and hormones

• 3 Main Types:– Oils, fats and waxes– Phospholipids– “Fused-ring” steroids

CO

HO

CO

HO

C OHHH

C OHH

C OHHH

glycerol fatty acids

CHCO

HOCH

+

etc.

etc.

etc.

CHCO

CO

CO

C OHH

C OH

OHH

triglyceride

CH

etc.

etc.

etc.O

HH

OHH

OHH

3 watermolecules

C

+

CH2 CH2 CH2 CH2 CH2 CH2 CH2

CH2

CH2

CH2

CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2

CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2

CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2

CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2

CH2 CH2 CH2 CH2 CH2 CH2 CH2

CH2

CH2

CH2carboxyl groups

FatsandOils

Fat Wax

Fats are efficient storage (9.3 Calories compared to 4.1 for sugars)

Waxes remain firm in outdoor temperatures

(Waxes are not a food source)

Beef fat (saturated)

Most saturated fat comes from animals, and should be eaten inlimited amounts

oleic acid

Linseed oil (unsaturated)

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Hydrogenation

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Cis- and Trans- Fatty Acids Compared

3.4 What Are Lipids?

• Phospholipids are similar to triglycerides

• Phospholipids Have Water-Soluble “Heads” and Water-Insoluble “Tails”

• These are crucial to the structure and function of the cellular membrane (and other plasma membranes)

polar head fatty acid tailsglycerolbackbone

CH3 O

OO

CH2 -CH2-CH2-CH2

(hydrophobic)(hydrophilic)

C-N-CH2-CH2-O-P-O-CH2 O

HC-O-C-

C-O-C-

CH3

H3

H2 CH2 -CH2-CH2-CH2-CH2 -CH2-CH2-CH2-CH2 -CH2-CH2-CH2-CH2 -CH2-CH2-CH3

-CH2 -CH2-CH2-CH2

CH2CH2

CH2CH2

CH2CH2

CH2CH3

CH2=-

- --

- - - -

3.4 What Are Lipids?• Steroids Consist of Four Carbon Rings

Fused Together

• One type of steroid is cholesterol

• Also used in – Animal cell membranes

– To synthesize other steroids including male and female sex hormones

– Hormones to regulate salt levels

– Bile to assist in fat digestion

HC

HC

HO

CH3

OH

HO

OH

O

cholesterol testosterone

estradiol

CH3

CH3

CH3

CH3

CH2

CH2

CH2

CH3

CH3

CH3

3.5 What Are Proteins?• Chains of amino acids

aminogroup

hydrogen

variablegroup

carboxylicacid group

O

CC

O

R

H

H

HH

N

Hair

Horn

Silk

C

O

C

H

CH2

C

H

H2N

C

O OH

OH

CH2

glutamic acid (glu)

C

O

C

H

H2N

CH2

C

H

OH

CH2

CH2

NH

C NH

NH2

arginine (arg)

C

O

C

H

H2N

CH2

C

H

OH C

O

C

H

H2N

CH2

C

H

OH

hydrophilic

CH

CH3hydrophobic

leucine (leu)phenylalanine (phe)

C

O

CH2N C

H

OH

cysteine (cys)

formsdisulfidebridges

CH2

SH

CH3

ss

s-s

ss

s-ss-s

ss

keratin

(Curly Hair!)

waterpeptide

peptidebond

amino acid

aminogroup

aminogroup

carboxylgroup

amino acid

carboxylgroup

• Amino Acids Are Joined to Form Chains by Dehydration Synthesis

3.5 What Are Proteins?• A Protein Can Have Up to Four Levels

of Structure– Primary is the sequence of amino acids– Secondary is any helix or pleated sheets– Tertiary is folding due to hydrophobic and

hydrophilic parts of the molecule plus disulfide bridges

– Quaternary is individual polypeptides linked together

• Denatured means to disrupt the secondary or tertiary structure

gly

leuleu

val

val

lys

lys

lys

lys

gly

gly

his

his

ala

ala

lys

lys

val

lys

pro

val

lyspro

Pleated sheet

hydrogenbond

polypeptide

R R R R R

RRRR

R R R

RRRR

CC

C C

CC

CC

CC

CC

CC

CC

C

CCC

CCCC

CCCCCC

CCCC

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

N N N N N N N

NN

NN

N

N

NN

N

R

R

H H H H

P O

O

OCH

H

OH

H HH

H

OH

HO

Deoxyribose nucleotide

phosphatebase

sugar

C

N CH

NC

C

N

HC

N

NH2

phosphate base

Nucleotide chain

sugar

3.6 What Are Nucleic Acids?

• Nucleic acids are longs chains of nucleotides

• DNA and RNA, the Molecules of Heredity, Are Nucleic Acids

• Other Nucleotides Act as Intracellular Messengers, Energy Carriers, or Coenzymes

P O

O

OH

P O

O

OH

P O

O

OH

HO

Vitamin

C

N CH

NC

C

N

HC

N

CH2

H

O

H

OH OH

HH

P O

O

O

HO

CH2

H

O

H

OH OH

HH

P OHO

O

C

N CH

NC

C

N

HC

N

C

N CH

NC

C

N

HC

N

NH2 NH2

NH2

CH2

H

O

H

O OH

HH

O P

O

OH

Cyclic adenosine monophosphate (cyclic AMP)(intracellular communication)

Adenosine triphosphate (ATP)(energy carrier)

Coenzyme (active in cellular

metabolism)