Polysaccharides, polypeptides, and nucleic acids consist of chains of sugars, amino acids, and nucleotides, respectively. The subunits of a polysaccharide are simple sugars linked by covalent bonds called glycosidic bonds. In this example, the two sugars are joined by α(1→4) glycosidic bonds. The numbers refer to the carbons involved in the linkage. Two simple sugars can be joined by a dehydration reaction, in which a carbon atom of one molecule reacts with a hydroxyl oxygen atom of the other, r