Lactose

lactose
    n 1: a sugar comprising one glucose molecule linked to a
         galactose molecule; occurs only in milk; "cow's milk
         contains about 4.7% lactose" [syn: {lactose}, {milk sugar}]
    

Galactose \Ga*lac"tose\, n. (Chem.)
   A white, crystalline sugar, {C6H12O6}, isomeric with
   dextrose, obtained by the decomposition of milk sugar, and
   also from certain gums. When oxidized it forms mucic acid.
   Called also {lactose} (though it is not lactose proper).
   [1913 Webster]
    

lactose \lac"tose`\ (l[a^]k"t[=o]s`), n.
   1. (Physiol. Chem.) The main sugar present in milk, called
      also {sugar of milk} or {milk sugar}. When isolated pure
      it is obtained crystalline; it is separable from the whey
      by evaporation and crystallization. It is a disaccharide
      with the formula {C12H22O11}, being chemically
      4-([beta]-D-galactosido)-D-glucose. It has a slightly
      sweet taste, is dextrorotary, and is much less soluble in
      water than either cane sugar or glucose. Formerly called
      {lactin}. When hydrolyzed it yields glucose and galactose.
      In cells it may be hydrolyzed by the enzyme
      [beta]-galactosidase.
      [1913 Webster +PJC]

   2. (Chem.) See {Galactose}.
      [1913 Webster]