Overview Peptide bond formation carboxyl group on one amino acid + amino group on another amino acid results in a loss of water bond can be broken (hydrolyzed) with addition of water across the bond Orders of protein shape primary amino acid sequence determined by covalent peptide bonds secondary stable folding of individual protein domains a protein may have combinations of different secondary structures common forms α-helix, β-pleated sheet determined by amino acid-amino acid interactions via hydrogen bonds tertiary shape of protein as a whole which imparts functionality to a protein shape may be disrupted (denatured) with changes in solution common forms globular, fibular determined by h-bonding, hydrophobicity, disulfide bridges, ionic bonds quaternary combination of tertiary sub-units examples α + β subunits in hemoglobin