BIOL 101 General Biology I

Chapter 4

Carbon & the Molecular Diversity of Life

Rob Swatski

Associate Professor of Biology

HACC – York Campus 1

Carbon: The Backbone of Life

• Living organisms consist mostly of carbon-based compounds

• Carbon is unparalleled in its ability to form large, complex, and diverse molecules

• Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds

2

Carbon: Life’s Backbone

3

Organic Chemistry

C

H

O

N

4

Vitalism

5

the idea that

organic compounds

arise only in

organisms

- was disproved when

chemists synthesized

these compounds

Mechanism

6

the view that all natural phenomena are governed

by physical and chemical laws

Organic Molecules and the Origin of Life on Earth

• Stanley Miller’s classic experiment demonstrated the abiotic synthesis of organic compounds

• Experiments support the idea that abiotic synthesis of organic compounds, perhaps near volcanoes, could have been a stage in the origin of life

7

Water vapor

“Atmosphere”

Electrode

Condenser

Cold water

Cooled water containing organic molecules

Sample for chemical analysis

H2O “sea”

EXPERIMENT

CH4

8

Electron Configuration

9

Valence

Hydrogen valence = 1

Oxygen valence = 2

Nitrogen valence = 3

Carbon valence = 4

H O N C

10

4 valence

electrons

4 covalent

bonds

Tetravalence

11

Valence Electrons of Carbon

Tetrahedral 12

Name and Comment

Molecular

Formula

(a) Methane

(b) Ethane

•CH4

Ball-and-

Stick Model

Space-Filling

Model

(c) Ethene (ethylene)

•C2H6

•C2H4

Structural

Formula

13

Carbon dioxide CO2

Urea CO(NH2)2

O = C = O

14

Carbon Skeletons & Molecular Diversity

15

Ethane Propane 1-Butene 2-Butene

Double bonds

Rings

Cyclohexane Benzene Butane 2-Methylpropane

(isobutane)

Branching

Length

16

Hydrocarbons

17

•Nucleus

•Fat droplets

(b) A fat molecule (a) Part of a human adipose cell

•10 m

18

Isomers

Structural

Cis-Trans

(Geometric) Enantiomers

19

Isomers

• Isomers are compounds with the same molecular formula but different structures and properties

– Structural isomers have different covalent arrangements of their atoms

– Cis-trans (Geometric) isomers have the same covalent bonds but differ in spatial arrangements

– Enantiomers are isomers that are mirror images of each other

20

Pentane

Structural isomers

Cis-Trans (Geometric)

isomers

2-methyl butane

cis isomer same

trans isomer across

Enantiomers

L isomer D isomer

21

• Enantiomers are important in the pharmaceutical industry

• Two enantiomers of a drug may have different effects

• Usually only one isomer is biologically active

• Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules

22

Dr. George Cotzias 1967

23

Enantiomers

L-dopa D-dopa inactive active

24

Drug

Ibuprofen

Albuterol

Condition

Pain, inflammation

Asthma

Effective Enantiomer

S-Ibuprofen

R-Albuterol

R-Ibuprofen

S-Albuterol

Ineffective Enantiomer

25

The Chemical Groups Most Important in the Processes of Life

• Functional groups are the components of organic molecules that are most commonly involved in chemical reactions

• The number and arrangement of functional groups give each molecule its unique properties

26

Functional groups

Estradiol Testosterone

27

Na+ Na+

Na+

Ca++ Ca++

Ca++

Ca++

28

7 Major Functional Groups

Hydroxyl group

Carbonyl group

Carboxyl group

Amino group

Sulfhydryl group

Phosphate group

Methyl group

29

STRUCTURE

EXAMPLE

Alcohols

-Their specific names usually

end in -ol. (may be written

HO—)

Ethanol

Is polar as a result

of the electrons

spending more

time near the

electronegative

oxygen atom.

Can form hydrogen

bonds with water

molecules, helping

dissolve organic

compounds such

as sugars.

Hydroxyl

30

Carbonyl STRUCTURE

EXAMPLE

Ketones if the carbonyl

group is within a

carbon skeleton

Aldehydes if the carbonyl

group is at the end of the

carbon skeleton

A ketone and an aldehyde may be structural

isomers with different properties, as is the

case for acetone and propanal.

Acetone

Propanal

Ketone and aldehyde groups are also found

in sugars, giving rise to two major groups of

sugars: ketoses (containing ketone groups)

and aldoses (containing aldehyde groups).

31

Carboxyl

Acetic acid

Carboxylic acids (organic acids)

Polar covalent bond

Carboxylate ion (-1)

Acetic acid Acetate ion

32

Amino

Amino acid

Amines

+1 Base

(ionized)

(nonionized)

Glycine

33

Sulfhydryl

Cysteine

S-containing amino acid

Thiols

Cross-linking covalent bonds

Protein shape

34

Phosphate

Chemical reactions

Phospholipid backbone

Glycerol phosphate

Organic phosphates

-2 or -1 charge

35

Methyl

DNA structure

5-Methyl cytidine

Methylated compounds

Gene expression

Hormone function

36

ATP: An Important Source of Energy for Cellular Processes

• One phosphate molecule, adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cell

• ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups

37

ATP

Adenosine triphosphate

Adenosine

38

Adenosine Triphosphate (ATP)

Primary source of chemical potential energy

Powers muscle

contraction, chemical transport, organelle

movement

Adenine, ribose, and 3

phosphate groups

39

40

•Energy P P P P i P P Adenosine Adenosine

ADP ATP

Reacts with H2O

•Energy

41

ATP Cycle

P i ADP +

H2O ATP + ATP

ATP hydrolysis

ATP synthesis

42

43

44