This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Amino acid required for formation of thyroxine? 
Select and explain. 
A. Tryptophan, B. Tyrosine, C. Glutamine, D. Cysteine
B: Tyrosine
Answer: B: Tyrosine 
Explanation: Ans. is 'b i.e., Tyrosine The term thyroid hormone denotes both thyroxine (7'4) and triodothyronine (T3). Both T4 and T3 are iodine derivatives of thyronine. Thyronine is a condensation product of two molecules of amino acid tyrosine. Thyroxine is 3, 5, 3', 5' - tetraiodothyronine and T3 is 3, 5, 3 '-triiodothyronine. Thyroid hormones are synthesized and stored in the thyroid follicles as apa of thyroglobulin molecule.