Question

Identify the monosaccharides and their linkages in the following disaccharide.

Short answer

The monomers in the given disaccharide are galactose and fructose. It contains β (1→6) glycosidic linkage.

Step-by-step solution

Identifying monosaccharides and disaccharides

The given Haworth ring structure is galactose and fructose. The monosaccharides,$\mathbf{galactose}\mathbf{,}\mathbf{}\mathbf{and}\mathbf{}\mathbf{fructose}\mathbf{}\mathbf{are}\mathbf{}\mathbf{combined}$to form a disaccharide called lactulose. Lactulose is a synthetic sugar used as a prebiotic ingredient.

Linkage formation

Galactose is an aldose, while fructose is a ketose sugar. The carbon 1 of the monosaccharide β -D-galactose is involved in the glycosidic linkage with the carbon 6 of β-D- fructose. Thus, β(1-6) glycosidic linkage is formed in lactulose.