B IO C H E M IS T R Y PE A R L S
amino acid is used to identify those amino acids
that must be taken
through the diet and cannot be
There are ten such essential amino acids for which biosynthetic
pathways do not exist in cells of the human body.
Phenylalanine is an essential amino acid that is also used to gener-
ate the nonessential amino acid tyrosine.
Marks DB, Marks AD, Smith CM. Basic Medical Biochemistry: A Clinical
Approach. Baltimore, MD: Lippincott Williams & Wilkins, 1996:569-646.