Which amino acid is a precursor for melanin?

The correct choice is the amino acid tyrosine, as it plays a critical role in the biosynthesis of melanin. Melanin is a pigment that gives color to skin, hair, and eyes, and it is produced through a series of enzymatic reactions that begin with the amino acid tyrosine.

Tyrosine is converted into DOPA (3,4-dihydroxyphenylalanine) through the action of the enzyme tyrosinase. Following this step, DOPA undergoes further oxidation and polymerization processes, ultimately resulting in the formation of melanin. Thus, tyrosine is not only a building block for melanin but also serves as a vital precursor that initiates the complex biochemical pathway leading to the pigmentation.

This pathway underscores the importance of tyrosine in the synthesis of key biological molecules. Other amino acids listed, while important in various metabolic processes, do not directly lead to melanin production. For instance, arginine is primarily involved in the urea cycle and nitric oxide synthesis, tryptophan is a precursor for serotonin and melatonin, and glycine is an amino acid involved in protein synthesis and the production of other biomolecules, but none serve as precursors for melanin like ty