Formation of zwitterion in amino acids

Formation of most of the amino acids as well as adenine and other uncleic bases from inorganic moleciles was wxperimentally shown by :

Which of the two groups of the given formula is involved in peptide bond formation between different amino acids ?

Which of the two groups of the given formula is involved in peptide bond formation between different amino acids ?

Which of the two groups of the given formula is involved in peptide bond formation between different amino acids ?

An acidic amino acid is

An acidic amino acid is

An acidic amino acid is

Name two facts in support of zwitterion structure ofa-amino acids.