This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Tryptophan is: \nSelect and explain. \nA. Non polar, essential and pure glucogenic, B. Polar, essential and both glucogenic & ketogenic, C. Polar, non-essential, both glucogenic & ketogenic, D. Non polar, essential, both glucogenic & ketogenic', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D. Non polar, essential, both glucogenic & ketogenicTryptophan is a non-polar, heterocyclic amino acid. It acts as glucogenic as well as ketogenic amino acid. It is an essential amino acid as it helps in the formation of Niacin (active form NAD) and serotonin and melatonin.', 'role': 'assistant'}]