This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
Acidic amino acids are 
Select and explain. 
A. Asparagine, B. Arginine, C. Glutamine, D. None
D: None
Answer: D: None 
Explanation: aspaic acid and glutamic acid are proton donors. At physiologic pH, the side chains of these amino acids are fully ionized, containing a negatively charged carboxylate group (-COO-). They are, therefore, called aspaate or glutamate to emphasize that these amino acids are negatively charged at physiologic pH Asparagine and Glutamine are neutral amino acids. Ref: LIPPINCOTT's Biochemistry 6th Edition Pg No. 5.