Carbon Chemistry - 1
Although water is the most abundant compound of living organisms, and the
"medium" for the existence of life, the molecules that are comprise most of living
organisms fall into four categories: carbohydrates, lipids, proteins and
nucleic acids. These molecules are all based on the element, carbon, which has
the ability to form large, complex and diverse molecules.
Carbon's versatility provides for the uniformity of chemicals and atomic
proportions of the elements found in living organisms.
A living organism can
manufacture a multitude of different substances needed to sustain life from
simple carbon backbones that combine in precise ways with atoms of hydrogen,
oxygen, nitrogen, sulfur and phosphorus.
The variation among this multitude of
organic molecules from species to species and individual to individual distinguishes
one from another.
Before we examine the molecules of living organisms by reviewing the properties of
The chemistry of carbon, or carbon–hydrogen molecules, which are called
hydrocarbons, is the field of organic chemistry, and the organic molecules of
living organisms, biochemistry.
The specific properties of carbon-containing
molecules are derived from the functional groups, small molecular fragments
with specific chemical properties that bond to the hydrocarbon backbone,
affecting the chemical nature of the resulting compound.
Properties of Carbon
An atom's electrons determine the chemical characteristics and bonds an atom will
Carbon always forms covalent bonds to become stable.
You will recall that
a covalent bond is one in which one or more electrons is/are shared between
The carbon atom has 6 electrons, 2 in its inner shell (energy level) and 4 in
its outer energy level.
Carbon has a valence of 4 so each carbon atom makes 4
bonds to obtain 8 electrons in its outer shell. (
And generally in 4 different
This is known as carbon’s tetravalence.)
Carbon may make bonds with other carbon atoms forming chains, branching chains
or rings of linked carbon atoms.
Ring compounds are common in living organisms.
The bonding of carbons to carbons is called the carbon skeleton.
single covalent (bonding angle 109°, forming a tetrahedron shaped molecule),
double covalent and triple covalent bonds.
Double and triple bonds alter the
bonding angles and shape of the resulting molecule. Double-bonded carbon bonds,
for example, are flat.
As we will see many times the shape of molecules is critical
to molecular function.