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
[{'content': 'Source of norepinephrine is? \nSelect and explain. \nA. Phenylalanine, B. Alanine, C. Tyrosine, D. Tryptophan', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Tyrosine REF: Lehninger Principles of Biochemistry 4th Edition page 440, 678, and 859 "Tyrosine gives rise to a family of catecholamines that includes dopamine, norepinephrine, and epinephrine" "Norepinephrine is synthesized by a series of enzymatic steps in the adrenal medulla and postganglionic neurons of the sympathetic nervous system from the amino acid tyrosine"', 'role': 'assistant'}]