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
Beta alanine is a end product of 
Select and explain. 
A. Cysteine, B. Tyrosine, C. Serine, D. Glycine
A: Cysteine
Answer: A: Cysteine 
Explanation: β-alanine is a metabolite of cysteine.