This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
Catecholamine hormones are synthesized in the: 
Select and explain. 
A. Chromaffin cells of adrenal medulla, B. Zona glomerulosa of adrenal cortex, C. Zona fasciculate of adrenal cortex, D. Zona reticularis of adrenal cortex
A: Chromaffin cells of adrenal medulla
Answer: A: Chromaffin cells of adrenal medulla 
Explanation: Ans. A. Chromaffin cells of adrenal medullaCatecholamines are synthesized by tyrosine. DOPA forms Dopamine in the cytosol which by Dopamine oxidase (Cu containing) forms Nor-epinephrine in the Chromaffin granules of pheochromocyte. This reaction requires copper and Vitamin C. Nor-epinephrine then enters cytoplasm and undergoes methylation by methionine to form Epinephrine. Both after synthesis enters in the chromaffin granules for storage.