CARBON AND THE MOLECULAR
DIVERSITY OF LIFE
Chapter 4
Biology – Campbell • Reece
IMPORTANCE OF CARBON
 Organic
chemistry – the study of carbon
compounds
 Most versatile building blocks of
molecules
 It has 4 valence electrons
 Shares them in covalent bonds (not
likely to form ionic)
 It makes large complex molecules
possible.
 It determines an organic molecule’s
three dimensional shape
IMPORTANCE OF CARBON
 Variation
in carbon skeletons
contributes to the diversity of organic
molecules
Length
 Shape (straight, branched, ring)
 Number and location of double bonds
 Other elements covalently bonded to
available sites

HYDROCARBONS
 Contain
only carbon and hydrogen
 Have a diversity of carbon skeletons
which produce molecules of various
lengths and shapes
 Are hydrophobic because the C-C
and C-H bonds are nonpolar
 Biologically important molecules
(fats)
STRUCTURE OF HYDROCARBONS
ISOMERS
 Compounds
with the same molecular
formula but with different structures
and different properties


Structural isomers = differ in the covalent
arrangement of their atoms (and location
of double bonds)
Geometric isomers = share the same
covalent partnerships, but differ in spatial
arrangements.
cis isomer – on the same side of the double bond
 trans isomer – on opposite sides

ISOMERS
 Enantiomers
= isomers that are
mirror images of each other
Can occur when four different atoms or
groups of atoms are bonded to the same
carbon.
 Two different spatial arrangements
 Usually, one form is biologically active
and the other is not

ISOMERS
FUNCTIONAL GROUPS
 Contribute
to the molecular diversity
of life
Have specific chemical and physical
properties
 Are chemically active regions of organic
molecules
 Behave consistently from one organic
molecule to another
 Determine unique chemical properties
of the molecules in which they occur

HYDROXYL GROUP
CARBONYL GROUP
CARBOXYL GROUP
AMINO GROUP
SULFHYDRYL GROUP
PHOSPHATE GROUP
METHYL GROUP