Knowledge of amino acids and their structures and functions
is required for some courses in biology, health sciences, diet,
nursing, and related disciplines. This page is a summary of
key fact about Amino Acids - with links to pages about individual
acids (in the glossary section).
What are Amino Acids ?
There are over 20 amino acids, each one being subtely different
from the others - but all of them having similar basic structures
and similar / related functions within the body.
Two categories (groups) of Amino Acids:
There are two types of amino acid:
- Those that can be synthesized
by the body itself, and
- Those that (are necessary for
healthy growth or maintenance of the body) but cannot be
produced by the body itself.
The second type of amino
acids are called "Essential
Amino Acids", and are also referred
to as "Indispensible
Amino Acids" in some textbooks. Conversely,
those that can be produced within the body itself (generally
from an excess of certain other amino acids in the body)
are referred to as "Non-Essential" or "Dispensible" amino
acids because, although their presence in the right
quantity is important for good health, they are not essential within
a person's diet.
Which amino acids are in each category ?
The Structure / Chemistry of Amino Acids
(1) What do they have in common ?
All amino acid molecules include the following in their chemical
In chemistry, a carboxyl group is a functional group consisting
of a carbon atom double-bonded to an oxygen atom and single-bonded
to a hydroxyl (-OH) group, as indicated by the structure
drawn on the right.
Carboxyl groups are weakly acidic and are the characteristic
constituents of carboxylic acids. They are present in
most organic acids, and are biodegradable.
Amino means there is an -NH2 group.
When amino groups occur in organic substances (such as amino acids),
they are generally attached to a carbon atom.
Long strings, or "chains" of thousands
of the 20 amino acids that form proteins linking together
form the proteins that
exist in the body. These chains generally consist of repeated
sequences of specific amino acids.
(2) How do the amino acids differ from each other
It is the SIDE GROUPS which make each amino acid different
from the others.
Of the 20 amino acids used to make proteins, there are three
These three groups are:
These names refer to the way the side groups (sometimes called
"R" groups) interact with the environment.
Polar amino acids have a tendency to adjust themselves
in a certain direction. Non-polar amino acids don't
really care what's going on around them. Ions are
atoms (or, more accurately, parts of atoms) that are
charged because they have either gained or lost negatively
charged electrons. It is this difference in the charge
on ions that holds ionic substances together.