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': 'On consumption of which aminoacid, requirement of methionine is reduced because of sparing effect? \nSelect and explain. \nA. Homocysteine, B. Cysteine, C. Lysine, D. Arginine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., Cysteine"Adequate dietary source of cysteine \'spares\' methionine".* Methionine is an essential amino acid.* Methionine is required for synthesis of cysteine (thus cysteine is non-essential amino acid)* Thus, cysteine can spare the requirment of methionine in diet.', 'role': 'assistant'}]