Amino acids tend to be localized either in the interior or on the exterior of a globular protein molecule, depending on their relative affinities for water. For each of the following pairs of amino acids, choose the one that is more likely to be found in the interior of a protein molecule, and explain why: Explain why cysteine residues with free sulfhydryl groups tend to be localized on the exterior of a protein molecule, whereas those involved in disulfide bonds are more likely to be buried in the interior of the molecule.