Question

Which of the following statement is not true?

• A. Lactose contains $\mathrm{\alpha }-$glycosidic linkage between ${\mathrm{C}}_1$of galactose and ${\mathrm{C}}_4$of glucose
• B. Lactose is a reducing sugar and give fehling's test
• C. On acid hydrolysis, Lactose give one molecule of $\mathrm{D}(+)$ Glucose and one molecule of $\mathrm{D}(+)$ Galactose
• D. Lactose $\left({\mathrm{C}}_{11}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$is a disaccharide and it contains $8$hydroxyl groups.

Answer 1

The correct option is A

Lactose contains $\mathrm{\alpha }-$glycosidic linkage between ${\mathrm{C}}_1$of galactose and ${\mathrm{C}}_4$of glucose

The correct option is option A

The explanation for the correct option:

1. Lactose is a disaccharide and it naturally occurs in both cow's milk and human milk.
2. It has units of galactose and glucose.
3. These units are joined together by $1-4,$ beta-oriented glycosidic linkages.
4. Since Lactose contains an aldehyde group ($-\mathrm{CHO}$) that is oxidized into ($-\mathrm{COOH}$) when it reacts with an oxidant like Fehling's or Benedict's reagent, and hence Lactose is referred to as a "reducing sugar".
5. One equivalent of D-Glucose and one equivalent of D-Galactose are produced by the acidic hydrolysis of Lactose.
6. Some people are unable to digest Lactose and this condition is referred to as lactose intolerance.

Lactose contains $\mathrm{\alpha }-$glycosidic linkage between ${\mathrm{C}}_1$of galactose and ${\mathrm{C}}_4$of glucose is the incorrect statement.