<prompt> Keratin in skin is softer than keratin in nail because keratin in skin has -Less number of disulphide bondsLess number of salt bridgesHigh sodium contentDifferent affinity for water  <response>: The extent of keratin hardness depends on the number of disulfide bondssulfur content. The more the number of disulfate bonds, the harder the keratin is.Keratin in skin is softer than keratin in nails because it has less number of disulfide bonds. 