Question: what is tyrosine and tryptophan?
Answer: Tryptophan (l ‐tryptophan) is a precursor of serotonin [5‐hydroxytryptamine (5‐HT)], while phenylalanine and tyrosine are precursors of the catecholamine neurotransmitters dopamine, norepinephrine and epinephrine. ... Tryptophan cannot be synthesized de novo and must be supplied through the diet.