The Liver cont…..

The Liver cont…..
• Amino acids can be deaminated or
• Deamination produces ammonia which is
dangerous to the body
• Ammonia is converted to urea via the
ornithine cycle
• Transamination (or aminotransfer) is the
reaction between an amino acid and an alphaketo acid.
• The amino group is transferred from the former
to the latter; this results in the amino acid being
converted to the corresponding α-keto acid,
while the reactant α-keto acid is converted to the
corresponding amino acid (if the amino group is
removed from an amino acid, an α-keto acid is
left behind).
• Transamination is accomplished by
enzymes called transaminases or
• The human body synthesizes the 10 nonessential amino acids and transamination
is the process by which most of these
syntheses occur.
• Deamination is the removal of an amine group
from a molecule.
• In the human body, deamination takes place in
the liver. It is the process by which amino acids
are broken down.
• The amino group is removed from the amino
acid and converted to ammonia. The rest of the
amino acid is made up of mostly carbon and
hydrogen and is recycled or burned for energy.
• Ammonia is toxic to the human system,
and enzymes convert it to urea or uric
acid by addition of carbon dioxide
molecules in Urea Cycle.
• Urea and uric acid can safely diffuse into
the blood and then be excreted in urine.
• The urea cycle or the ornithine cycle
describes the conversion reactions of
ammonia into urea.
• Since these reactions occur in the liver,
the urea is then transported to the kidneys
where it is excreted. The overall urea
formation reaction is:
• 2 Ammonia + carbon dioxide + 3ATP --->
urea + water + 3 ADP