JAMB Biology 2018 Paper

Concept:A disaccharide is a carbohydrate formed by the chemical combination of two monosaccharide units.Explanation:Maltose is a disaccharide composed of exactly two glucose units linked together.The bond between them is an $\alpha(1\to4)$ glycosidic linkage, formed during the condensation of the two glucose molecules.Its molecular formula is $\mathrm{C}_{12}\mathrm{H}_{22}\mathrm{O}_{11}$.When maltose undergoes hydrolysis, it splits into two molecules of glucose:$$\mathrm{C}_{12}\mathrm{H}_{22}\mathrm{O}_{11} + \mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$Therefore, maltose is glucose + glucose.The other options are incorrect: sucrose is a combination of glucose and fructose, galactose is a single monosaccharide, and fructose is another single monosaccharide.Answer:Glucose (Option A).