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KS5 Biology
Lesson Plan 7 – Thin Layer Chromatography
Science at Work in Healthcare
Post – 16 Science Education Pack
Resource Sheet 7.2 – Amino Acids
What are amino acids?
Amino acids are compounds with the general formula H2NCHRCOOH, where R is an
organic substituent. The structure is shown below.
Diagrams of the naturally occurring amino acids are given below. Those essential amino
acids are marked with an asterisk. In this case the word essential doesn’t mean they are
any more important than any of the others. It actually means that they cannot be
synthesized by the body so need to be accounted for in our diets.
KS5 Biology
Lesson Plan 7 – Thin Layer Chromatography
Science at Work in Healthcare
Post – 16 Science Education Pack
However, cysteine, tyrosine, histidine and arginine could be called semi-essential amino
acids as children are unable to synthesize them because the relevant metabolic pathways
are not fully developed.
What do we use amino acids for?
Amino acids play central roles in our bodies both
as building blocks of protein and as intermediates
in metabolism.
Amino acids join to form proteins when the amino
group of one acid reacts with the carboxyl group of
another. This reaction is called a condensation
reaction as a water molecule is removed in the
process. The two amino acids are joined with a
peptide link to form a dipeptide. Further
condensation reactions add more amino acids to
the dipeptide to form a polypeptide. A typical
protein is made up of one or more polypeptide chains
which may be folded, branched and also cross-linked
Diagram 1. Structure of a typical
protein
by hydrogen bonds, ionic bonds or sulphur bridges.
The precise content and the sequence of amino acids making up a specific protein is
determined by the sequence of the bases in the gene that encodes that protein. The
resulting chemical properties of the protein determine its biological activity.
The total number of amino acids making up a protein molecule can range from a few to
several thousand. As an example of a large protein, serum globulin has a relative molecular
mass of 140 000.
As proteins not only catalyze the vast majority of reactions in living cells, they control
virtually all of the cellular processes. This makes amino acids vital for life. In addition,
proteins contain within their amino acid sequences the information needed to determine how
that protein can fold into a three dimensional structure. The field of protein folding and
stability has been a critically important research area for years, and even today it still
remains as one of the great unsolved mysteries of biology.