Which of the statements about peptide bonds are true?
A. Peptide bonds are ester linkages.
B. Peptides are polymers of amino acids.
C. A tetrapeptide contains five amino acid residues.
D. Peptide bond formation is a hydrolysis reaction.
E. Peptide bonds form from nucleophilic attack by an electron pair on an ??amino nitrogen atom on an ??carboxyl carbon atom of another amino acid.