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SIMON’S GUIDE TO PROTEINS
Some foods containing protein
FUNCTIONS OF PROTEINS
Protein has a range of essential functions in the body,
including the following:
• Required for building and repair of body tissues
(including muscle)
• Enzymes, hormones, and many immune molecules are
proteins
• Essential body processes such as water balancing,
nutrient transport, and muscle contractions require
protein to function.
• Protein is a source of energy.
• Protein helps keep skin, hair, and nails healthy.
• Protein, like most other essential nutrients, is absolutely
crucial for overall good health.
PROTEINS AND YOUR DIET
Proteins are therefore an essential component of
your daily diet.
The Recommended Daily Allowance (RDA) of
protein according to U.S. government standards
is 0.8 gram per kilogram (2.2 pounds) of ideal
body weight for the adult. A person weighing 10
stone (about 64 kg) therefore needs about 50 g
of protein per day
WHAT ARE PROTEINS?
Proteins are condensation polymers made
from amino acids. The structure, and
therefore the function, of a protein
depends entirely on the amino acid
sequence. During digestion, proteins
undergo hydrolysis and are split up into
their component amino acids. The body
can then use these as building blocks to
make the proteins it needs.
This structure is known
as a zwitterion. Amino
acids are therefore
solids that are soluble in
water, like other ionic
compounds.
Which is the only amino acid that does not show optical isomerism?
IONISATION OF AMINO ACIDS
• In solution at pH 7, amino acids occur as zwitterions.
• Below pH 7 the carboxyl group will become increasingly less ionised
(like any carboxylic acid) , whilst the amino group remains ionised:
+
H3NCHRCOO- + H+ = +H3NCHRCOOH
If the R group contains carboxyl groups or amino groups then these
will be affected similarly.
• Above pH 7, the amino group will become increasingly less ionised
(like any amine), whilst the carboxyl group remains ionised:
+
H3NCHRCOO- + OH- = H2NCHRCOO- + H2O
If the R group contains carboxyl groups or amino groups then these
will be affected similarly.
These properties affect the separation of amino acids by a process
called electrophoresis which you will learn about later.
LEVELS OF PROTEIN STRUCTURE
• Primary: the sequence of amino acids in the
chain
• Secondary: folding of the chain caused by
hydrogen bonding between different peptide
bonds
• Tertiary: folding of the chain caused by
interactions between the R groups
• Quaternary: interactions between different
chains (subunits) of the same protein
PRIMARY PROTEIN
STRUCTURE
SECONDARY PROTEIN
STRUCTURE
TERTIARY PROTEIN
STRUCTURE
QUATERNARY PROTEIN STRUCTURE
OVERALL PROTEIN STRUCTURE
And now for something completely
different …
About time,
too!
• One of Simon’s holiday pictures
• Where was this picture taken?
• (Answer on final slide )
Where are Simon and Dee sheltering from the
rain?
Answer
Hiroshima, Japan
The “A bomb dome”
THE END