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': 'Which among the following amino acid is heterocyclic in structure? \nSelect and explain. \nA. Histidine, B. Phenylalanine, C. Hydroxyproline, D. Proline', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Histidine and tryptophan are heterocyclic amino acids. Phenylalanine and tyrosine are aromatic amino acids. Proline is an imino acid. Hydroxyproline, hydroxylysine, and ornithine are derived amino acids. Ref: Textbook of Biochemistry for Medical Students By Dm Vasudevan, 2010, Page 20.', 'role': 'assistant'}]