1. Chapter 4 Carbon and the Molecular Diversity 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. Concept 4.1: Organic chemistry is the study of carbon compounds
Organic chemistry is the study of compounds that contain carbon.
Organic compounds range from simple molecules to colossal ones.
Most organic compounds contain hydrogen atoms in addition to carbon atoms.

3. Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms
Carbon has 6 electrons, with 2 in the first electron shell and 4 in the second shell; thus it has 4 valence electrons in a shell that holds 8 electrons.
Carbon atom usually completes its valence shell by sharing its 4 valence electron.
Carbon can form up to 4 covalent bonds.
Each carbon acts as an intersection point from which a molecule can branch off in as many as four directions.
This ability is one facet of carbon’s versatility that makes large, complex molecules present.

4. When the carbon atoms in a molecule each are bonded to 4 other atoms, every grouping of a carbon has a tetrahedral shape.
Bond angle = 109.5°
When two carbon atoms are joined by a double bond, the atoms joined to those carbons are in the same plane as the carbons.

5. Name and Comment Molecular Formula Structural Formula Ball-and-
Stick Model
Space-Filling
Model
(a) Methane
CH4
(b) Ethane
C2H6
Figure 4.3 The shapes of three simple organic molecules.
(c) Ethene (ethylene)
C2H4

6. The electron configuration of carbon gives it covalent compatibility with many different elements
Carbon dioxide: CO2
Urea: CO(NH2)2

7. Molecular Diversity Arising from Carbon Skeleton Variation
Carbon chains form the skeletons of most organic molecules.
The skeletons vary in length and may be straight, branched, or arranged in closed rings.
Some carbon skeletons have double bonds, which vary in number and location.
Such variation in carbon skeletons is one important source of the molecular complexity and diversity that characterize living matter.
Atoms of other elements can be bonded to the skeletons at available sites.

8. 2-Methylpropane (isobutane)
Figure 4.5
(a) Length
(c) Double bond position
Ethane
Propane
1-Butene
2-Butene
(b) Branching
(d) Presence of rings
Figure 4.5 Four ways that carbon skeletons can vary.
Butane
2-Methylpropane
(isobutane)
Cyclohexane
Benzene

9. Hydrocarbons
Hydrocarbons are organic molecules consisting of only carbon and hydrogen.
Many organic molecules, such as fats, have hydrocarbon components.
Hydrocarbons can undergo reactions that release a large amount of energy.
Hydrocarbons do not readily dissolve in water because most bonds are nonpolar carbon-to- hydrogen linkages.

10. Concept Check: Identify the asymmetric carbon in this molecule.
Asymmetric carbons occur when a carbon is bonded to four different groups or atoms.

11. Isomers
Isomers are compounds with the same molecular formula but different structures and properties.
There are three major types of isomers:
Structural isomers
Cis-trans isomers
Enantiomers

12. Structural isomers differ in the covalent arrangements of their atoms.
Figure 4.7 Three types of isomers, compounds with the same molecular formula but different structures.

13. Enantiomers
CO2H
CO2H H
NH2
NH2 H
CH3
CH3
L isomer
D isomer
Enatiomers differ in spacial arrangement around an asymmetric carbon, resulting in molecules that are mirror images.
Figure 4.7 Three types of isomers, compounds with the same molecular formula but different structures.

14. Cis-trans isomers differ in arrangement about a double bond.
cis isomer: The two Xs are on the same side.
trans isomer: The two Xs are on opposite sides.
Cis-trans isomers differ in arrangement about a double bond.
Figure 4.7 Three types of isomers, compounds with the same molecular formula but different structures.

15. Concept Check: What type of isomers are these two molecules?
Figure 4.UN10 Test Your Understanding, question 11

16. Concept 4.3: 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.

17. Adenosine
Figure 4.UN04 In-text figure, p. 66

18. One phosphate may be split off as a reaction with water.
Reacts
with H2O
Adenosine
Adenosine
Energy
ATP
Inorganic
phosphate
ADP
One phosphate may be split off as a reaction with water.
Creates one inorganic phosphate ion (HOPO32-).
ATP becomes adenosine diphosphate, or ADP.
Although ATP is sometimes said to store energy, it is more accurate to think of it as storing the potential to react with water.
Figure 4.UN05 In-text figure, p. 66