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': 'Amino-acid substitute for tryptophan without altering proteins characteristics ? \nSelect and explain. \nA. Tyrosine, B. Phenylalanine, C. Methionine, D. Alanine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is `b\' i.e., Phenylalanine Tryptophan is an aromatic amino acid, thus it can only be replaced with other aromatic amino acid.Other two aromatic amino acids are :?PhenylalanineTyrosineAmong these two, phenylalanine can substitute tryptophan but not tyrosine becausePhenylalanine and tryptophan both are hydrophobic (non-polar).Whereas, tyrosine is hydrophilic (Polar)."The only other aromatic residue that can substitude for tryptophan is phenylalanine. Tyrosine cannot substitute since it has hydrophilic propey"', 'role': 'assistant'}]