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
At physiological pH, which of these amino acids has a positive charge? 
Select and explain. 
A. Valine, B. Aspaic acid, C. Arginine, D. Isoleucine
C: Arginine
Answer: C: Arginine 
Explanation: Ans: C. ArginineAt physiological pH, arginine has a positive charge.Negative Charged (Acidic Side Chains) - Aspaic acid & glutamic acid.Positive Charged (Basic Side Chains) - Histidine, arginine & lysine.