to represent molecules. This is a diagrammatic language that may
look mysterious and obscure when you don’t know the rules (as any
language would), but it is actually pretty easy to understand once you
know a few rules.
= oFluoxetineLet’s talk about these rules. First, molecules produced by life (organic
molecules, organic from organism) are composed largely of carbon
and hydrogen and may contain dozens or hundreds or thousands of
atoms. While the most abundant atom in an organic molecule is usu-
ally hydrogen, carbon atoms form the scaffold that defines the overall
shape of the molecule. Hydrogen, though numerous, has only a single
electron to share and so can form only one chemical bond at a time.
It has no possibility of forming the scaffold for a molecule and can
only be stuck around the edges. Carbon, however, has four electrons
available for sharing, and each carbon atom can form four bonds and
be covalently joined to up to four other atoms. This allows carbon to
form the structural framework for molecules that can become very
large. Oxygen has two electrons to share and so can form two bonds.
Nitrogen has three electrons to share and thus is able to form three
bonds. Largely from these four elements—carbon, hydrogen, oxygen,
and nitrogen—are built the basic structures of an enormous number
of biologically interesting molecules.
To understand the diagrammatic rules for molecular structure,