This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Methionine and Cysteine details, Subject name: Biochemistry
[{'content': 'Which of the following dietarily non-essential amino acid becomes dietarily essential in patients of homocystinuria? \nSelect and explain. \nA. Cysteine, B. Methionine, C. Homocysteine, D. Phenylalanine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cysteine is dietarily not essential since it can be synthesised from the essential amino acid methionine In homocystinuria, methionine to cysteine conversion is affected So,Cysteine becomes essential in diet. Extra edge:- Tyrosine becomes dietarily essential in patients of phenylketonuria.', 'role': 'assistant'}]