is conjugate base of is conjugate acid of is substituent group from chemical entity organic group amino-acid residue amino acid residue amino-acid residues CHEBI:33708 amino acid residues chebi_ontology When two or more amino acids combine to form a peptide, the elements of water are removed, and what remains of each amino acid is called an amino-acid residue. protein amino acid cationic amino-acid residue anionic amino-acid residue