<P> The reducing end of a disaccharide is the monosaccharide with a free anomeric carbon that is not involved in a glycosidic bond and is thus capable of converting to the open - chain form . Recall that disaccharides consist of two monosaccharides and may be either reducing or nonreducing . However, even a reducing disaccharide will only have one reducing end, as disaccharides are held together by glycosidic bonds, which consist of at least one anomeric carbon . With one anomeric carbon unable to convert to the open - chain form, only the free anomeric carbon is available to reduce another compound . A nonreducing disaccharide has both anomeric carbons tied up in the glycosidic bond . </P> <P> Similarly, reducing polysaccharides have only one reducing end, assuming that there is no branching . </P> <P> All monosaccharides are reducing sugars because all monosaccharides have an aldehyde group (if they are aldoses) or can tautomerize in solution to form an aldehyde group (if they are ketoses). This includes common monosaccharides like galactose, glucose, glyceraldehyde, fructose, ribose, and xylose . </P> <P> Many disaccharides, like cellobiose, lactose and maltose, also have a reducing form, as one of the two units may have an open - chain form with an aldehyde group . However, sucrose and trehalose, in which the anomeric carbons of the two units are linked together, are nonreducing disaccharides since neither of the rings is capable of opening . </P>

What functional group in glucose has reducing properties