The shape of hair is determined in part by the pattern of disulfide bonds in keratin, its major protein. from first to last, arrange the five steps needed to induce permanent curls in hair. first step last step last step answer bank keratin's a-helices convert to b-sheets. keratin's disulfide bonds break. physically curl the hair. apply an oxidizing agent. keratin's disulfide bonds reform to hold shape. apply a thiol-containing reagent and gentle heat. keratin's amino acids rearrange into the curled conformation.