Question

The amino acid tyrosine is the precursor for the synthesis of
(i) Melatonin
(ii) Triiodothyronine
(iii) Thyroxine
(iv) Calcitonin

• A. ii and iii
• B. i and iv
• C. iii and iv
• D. i and ii

Answer 1

The correct option is A ii and iii

The amino acid tyrosine is a precursor of the thyroid hormones triiodothyronine or $T_3$ and tetraiodothyronine or thyroxine or $T_4$.

The precursor of melatonin is the amino acid tryptophan. Melatonin, triiodothyronine, and thyroxine are small organic molecules.

Calcitonin is a much larger molecule. It is a peptide of 32 amino acids.