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
Which amino acid migrates fastest on chromatography on carboxy methylcellulose medium? 
Select and explain. 
A. Aspaic acid, B. Valine, C. Lysine, D. Glycine
A: Aspaic acid
Answer: A: Aspaic acid 
Explanation: Ai.e. Aspaic acidIn cation exchange chromatography solid stationary matrix has negatively charged groups (i.e. -ve charged carboxy methyl cellulose, 0 - CH2 - COO- is used as cation exchanger). So in the mobile phase, proteins with a net positive charge (i.e. cations) move slowly than those with net negative charge (anion)Q. Hence aspaate (aspaic acid) being a negatively charged amino acid will move fastest in carboxymethyl cellulose or methanol chloroform (cation exchanger) ion exchange chromatography.