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
[{'content': 'Catecholamine hormones are synthesized in the: \nSelect and explain. \nA. Chromaffin cells of adrenal medulla, B. Zona glomerulosa of adrenal cortex, C. Zona fasciculate of adrenal cortex, D. Zona reticularis of adrenal cortex', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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.', 'role': 'assistant'}]