This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Phenylalanine and Tyrosine metabolism Detail, Subject name: Biochemistry
Which of the following chemical reaction is involved in the conversion of noradrenaline to adrenaline? 
Select and explain. 
A. Hydroxylation, B. Carboxylation, C. Methylation, D. Dehydrogenation
C: Methylation
Answer: C: Methylation 
Explanation: Catecholamines are derivatives of phenylalanine/tyrosine. "Nor" in noradrenaline (norepinephrine) indicates the absence of methyl group. The methyl group of adrenaline (epinephrine) is derived from S-Adenosyl methionine (AdoMet)