Explain why chemists

refer to the joining of monosaccharides molecules to form disaccharides as a "dehydration

synthesis" reaction. (aka: condensation reaction).

It is referred to as a hydration/condensation reaction because this reaction involves the production of a water molecule as a by-product of the formation of the glycosidic bond. When two monosaccharides join, the 4' C of one monomer forms a covalent bond the 1' C of the other. One Carbon loses an - OH while the other a - H during the formation of this bond. An H + and an OH - then combine to form a water molecule.