Structure, Formation &
• Proteins are large, important and
complex molecules (polymers) found in
• They are involved in most reactions in
• Each protein within the body has a
• The main functions of proteins in the
body are structural, maintenance and
regulation of life processes.
• Proteins which fulfil different roles in the
body are formed by linking differing
sequences of amino acids together.
• Proteins can be classified as fibrous or
• this structure is driven by hydrogen bonding
within the protein molecule.
• Animal tissue
• Skin, hair, nails
• Maintenance and regulation
of life processes
• Enzyme (amylase)
• Hormones (insulin)
• Transport (Haemoglobin)
• Antibodies (immune
Proteins which are enzymes
• An enzyme is a protein which is able
to catalyse a biochemical reaction
• The shape of the active site allows
specific reactants known as substrates
to attach, like a lock and key.
• Incorrect substrates are unable to fit
the shape of the active site and are not
• Proteins are constructed from building
blocks called amino acids.
• Amino acid molecules have two
– carboxyl group (-COOH)
– amino group (-NH2)
essential amino acids
• The body cannot make all the amino
acids required for body proteins and is
dependent on dietary protein for supply
of certain amino acids known as
essential amino acids.
Haemoglobin transport in
in the body or
• These proteins
are specific to
needs and are
built up within
the body by
• Here,the amino group on one amino acid
and the carboxyl group on a
neighbouring amino acid molecule join
together, with the elimination of water.
Amide Links (Peptide Links)
• The link which forms between the two
amino acids is called an amide link
(CONH) (also known as a peptide link).
Digestion of proteins
• Proteins obtained by eating plants or
animals are broken up during digestion
by a process called hydrolysis to
produce amino acids.
• You can work out the structural formulae of
the amino acids obtained from hydrolysis by
looking at the structure of a section of the
• Example 1
Work out the structures of the 3 amino acids
which would be obtained from hydrolysis of
the following Tri - peptide molecule
Lab analysis: chromatography
• Hydrolyse the protein using acid or alkali and
then use chromatography
• Using known amino acids alongside the
hydrolysed protein allows identification of
the amino acids in the protein.
• A, B, C, D and E - five known amino acids.
• P - hydrolysed protein.
• P contains four amino acids because 4 spots are
• The hydrolysed protein also contains another
unknown amino acid.
• This can be identified by running another
chromatogram with different known samples of
pure amino acids.