Question

Based on the context given below, answer the following questions:
Glycine is most often used as a buffering agent in biochemical experiments. This diprotic amino acid has a pKa value of 2.4 owing to carboxyl group and 9.6 owing to amino group. Glycine can exist as a zwitterion which can exist in either protonated form$(NH^+_3 )$ or as a free base $(-NH_2)$because of the reversible reaction: