Question

Observe the following statements.
I. Sucrose has glycosidic linkage.
II. Cellulose is present in both plants and animals.
III. Lactose contains $D$-galactose and $D$-glucose units.
Which of the following statements are correct?

• A. (I), (II) and (III)
• B. (I) and (II)
• C. (II) and (III)
• D. (I) and (III)

Answer 1

Answer: (D)

In sucrose, two monosaccharides are held together by a glycosidic linkage between $C_1$ of $\alpha$ -glucose and $C_2$ of $\beta$ -fructose. Cellulose occurs exclusively in plants and it is the most abundant organic substance in plant kingdom. Lactose is composed of $\beta$ -D-galactose and $\beta$ -D-glucose. The linkage is between $C_1$ of galactose and $C_4$ of glucose. Hence, statements (I) and (III) are correct.