Noun
An
essential amino acid
C
<
sub
>
9
sub
>
H
<
sub
>
11
sub
>
NO
<
sub
>
2
sub
>
found
in
most
animal
proteins
;
it
is
essential
for
growth
;
the
inability
to
metabolize
it
leads
to
phenylketonuria
;
it
is
a
constituent
of
aspartame
.