Amino Acids are the Sub-Units which are polymerized to form Polypeptide
chains (Proteins)
Proteins are long polymers in which the subunits are amino acids.
Every amino acid has 4 salient features:
amino group
carboxyl group
R group
the a
carbon is the central carbon which links each of the 3 groups together.
Every amino acid has the same structure in that it
always has an amino group linked to a carboxylic
acid group through the a carbon. However,
amino acids have different structures because the R
group (or side
chain) is different for each kind of amino
acid. This image shows
the 20 amino acids which make up proteins.
The amino acid part - which is the same in all amino
acids - is shown in
red.
The side chain, or "R" group - which is different
in all amino acids - is shown in
blue.
Since the R groups found in the 20 biologically important
amino acids are each different chemicals, it is to be expected that they
have different chemical properties. In fact the amino acids are usually
classified by the properties of their side chains:
hydrophilic (water soluble), positively charged
hydrophilic (water soluble), negatively charged
hydrophilic (water soluble), neutral
hydrophobic (insoluble in water), neutral
moderate polarity (slightly soluble in water), neutral
RETURN to the Protein
Structure Page to see how Amino Acids are chained together
to form Proteins.
