The difference in molecular weight between Phenylalanine & Tyrosine is by :: (A) 17, (B) 16, (C) 64, (D) 32
Answer is B. Usually students tend to mark 17 as the answer. Phenylalanine gets conveed to Tyrosine by enzyme Phenylalanine Hydroxylase. Most Hydroxylases are Mono-oxygenases i.e. EC No. 1. In hydroxylation reactions, only one oxygen atom from the molecular oxygen is added because H was already present in the phenylalanine. So, change in molecular weight is by 16 and NOT 17. Extra Information: Phenylalanine is an essential amino acid and its only role in the body is to give rise to tyrosine.