This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amino Acids Basics, Subject name: Biochemistry
Cysteine is synthesized from - 
Select and explain. 
A. Methionine, B. Arginine, C. Histidine, D. Lysine
A: Methionine
Answer: A: Methionine 
Explanation: Ans. is 'a' i.e., Methionine o The question is very simple.o One sulfur containing amino acid can be synthesized from other sulfur containing amino acid only,o Methionine and cysteine are sulfur containing amino acid.