1. Chapter 4: Carbon

2. Carbon Overview: Carbon—The Backbone of Biological Molecules
All living organisms are made up of chemicals based mostly on the element carbon
Organic chemistry is the study of carbon compounds

3. The Formation of Bonds with Carbon
Carbon has four valence electrons
This allows it to form four covalent bonds with a variety of atoms

4. The bonding versatility of carbon
Allows it to form many diverse molecules, including carbon skeletons
(a) Methane
(b) Ethane
(c) Ethene (ethylene)
Molecular Formula
Structural Formula
Ball-and-Stick Model
Space-Filling Model H C
CH4
C2H6
C2H4
Name and Comments

5. Common Bonding Partners of Carbon
The electron configuration of carbon
Gives it covalent compatibility with many different elements H O N C
Hydrogen
(valence = 1)
Oxygen
(valence = 2)
Nitrogen
(valence = 3)
Carbon
(valence = 4)

6. Which of the structures in this figure is an impossible covalently bonded molecule?
Answer: c
Source: Barstow - Test Bank for Biology, Sixth Edition, Question #28

7. Molecular Diversity Arising from Carbon Skeleton Variation
Carbon chains
Form the skeletons of most organic molecules
Vary in length and shape H C
(a) Length
(b) Branching
(c) Double bonds
(d) Rings
Ethane
Propane
Butane
2-methylpropane
(commonly called isobutane)
1-Butene
2-Butene
Cyclohexane
Benzene

8. Hydrocarbons Hydrocarbons
Are molecules consisting of only carbon and hydrogen
The bonds between the C and H atoms are non-polar covalent
This makes hydrocarbons hydrophobic

9. (b) Mammalian adipose cells
Hydrocarbons
Hydrocarbons
Are found in many of a cell’s organic molecules
(a) A fat molecule
(b) Mammalian adipose cells
100 µm
Fat droplets (stained red)

10. Isomers
Isomers
Are molecules with the same molecular formula but different structures and properties

11. (a) Structural isomers
Three types of isomers are
Structural
Geometric
Enantiomers H
CO2H
CH3
NH2 C X
(a) Structural isomers
(b) Geometric isomers
(c) Enantiomers

12. Why are Enantiomeric isomers important?
Enzymes distinguish between enantiomers! H
CO2H
CH3
NH2 C X
(a) Structural isomers
(b) Geometric isomers
(c) Enantiomers
Enzyme activity = 100 %
Enzyme activity = 0 %

13. Structure and Function
Subtle changes in structure can dramatically affect the molecule’s function

14. The Functional Groups Functional groups
Are the chemically reactive groups of atoms within an organic molecule
They behave consistently and characteristically, giving unique properties to the molecules possessing them.

15. Six functional groups are important in the chemistry of life
Hydroxyl
Carbonyl
Carboxyl
Amino
Sulfhydryl
Phosphate

16. Functional Groups  OH FUNCTIONAL GROUP STRUCTURE
(may be written HO )
HYDROXYL CARBONYL CARBOXYL OH
In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.)
When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH). C O
The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond. 

17. Acetone, the simplest ketone
Functional Groups
HYDROXYL
CARBONYL
CARBOXYL
Acetic acid, which gives vinegar its sour tatste
NAME OF COMPOUNDS
Alcohols (their specific names usually end in -ol)
Ketones if the carbonyl group is within a carbon skeleton
Aldehydes if the carbonyl group is at the end of the carbon skeleton
Carboxylic acids, or organic acids
EXAMPLE
Propanal, an aldehyde
Acetone, the simplest ketone
Ethanol, the alcohol present in alcoholic beverages H C OH O

18. Functional Groups
The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton.
AMINO SULFHYDRYL PHOSPHATE
(may be written HS )
The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape.
In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . N H SH O P OH

19. Functional Groups Ethanethiol Glycine Glycerol phosphate AMINO
SULFHYDRYL
PHOSPHATE
Because it also has a carboxyl group, glycine is both an amine and a carboxylic acid; compounds with both groups are called amino acids.
Glycine
Ethanethiol
Glycerol phosphate O C HO H H N C
SH
OH O P
O

20. Effect of Different Functional Groups
Functional groups give organic molecules distinctive chemical properties
CH3 OH HO O
Estradiol
Testosterone
Female lion
Male lion

21. Key Points of Chapter 4
Organic chemistry is the study of carbon compounds
Carbon atoms can form diverse molecules by bonding to 4 other atoms
Functional groups are the parts of molecules involved in chemical reactions and behave chemically in expected manners

22. Chapter 4 Essay Question
Discuss the biological importance of each of the following organic compounds in relation to cellular structure and function in plants and animals.
a. Carbohydrates
b. Proteins
c. Lipids
d. Nucleic acids