The amino group of one amino acid can be condensed with the carboxyl group of another amino acid to form a peptide, and the resulting amide group is called a peptide bond in protein chemistry. The molecule of amino acid is the smallest, and the protein is the largest. Two or more amino acids are dehydrated and condensed to form a number of peptide bonds to form a peptide chain. Multiple peptide chains are folded at multiple levels to form a protein molecule.