Chapter 4: Carbon and the Diversity
of Life
• Organic molecules: molecules that contain
carbon
Carbon: valence of 4
form 4 covalent bonds
Variations in carbon skeletons contribute to the
diversity of organic molecules.
Hydrocarbons: molecules containing only
carbon and hydrogen
-are hydrophobic and nonpolar
Major component of many Lipids (fats)
Isomers
• compounds with the same molecular
formula but with different structures (hence
different properties)
Three types of isomers [Figure 4.6]
• Structural isomers – covalent partners
• Geometric isomers – rearrangement around
double bond (rhodopsin)
• Enantiomers – 3-D shape /mirror image
- require asymmetric carbons
Functional Groups
• contribute to molecular diversity and behave
consistently from one organic molecule to
another
Hydroxyl Group
– consists of a hydrogen atom bonded to an
oxygen atom, which in turn is bonded to
carbon (-OH)
 Contributes polarity
 Organic compounds with hydroxyl groups are
called alcohols
Carbonyl Group
– consists of a carbon atom double bonded to
an oxygen (-C=O)
 Contributes polarity
 A functional group found in sugars
 aldehyde(“hides at end”) or ketone (“right
at home, mixing in)
Carboxyl Group
• consists of a carbon atom which is both doublebonded to an oxygen and single-bonded to a
hydroxyl group
(-COOH)
 Contributes polarity
 hydrogen reversibly dissociates as H+ (acidic
properties).
 Compounds with this functional group are called
carboxylic acids.
Amino Group
– consists of a nitrogen atom bonded to two hydrogens
and to the carbon skeleton (-NH2).
 Contributes polarity
 Acts as a weak base. The unshared pair of electrons on
the nitrogen can accept a proton, giving the amino
group a +1 charge.
 Organic compounds with this functional group are
called amines.
Sulfhydryl Group
– consists of an atom of sulfur bonded to an
atom of hydrogen (-SH).
* Contributes polarity
 Help stabilize the structure of proteins
 Organic compounds with this functional group
are called thiols.
Phosphate Group
– Functional group which is the dissociated form of
phosphoric acid (H3PO4) (-OPO3)
 Contributes polarity
 The loss of two protons by dissociation leaves the
phosphate groups with a negative charge.
 Has acidic properties since it loses protons
 Organic phosphates are important in cellular
energy storage and transfer (i.e., ATP)
Methyl Group
– Functional group which consists of a carbon
and three hydrogen atoms (-CH3)
 Nonpolar group (hydrophobic)