Biomolecules - Result Question 5
####5. Which one of the following statements is not true regarding $(+)$ Lactose?
[2011]
(a) On hydrolysis (+) Lactose gives equal amount of $D(+)$ glucose and $D(+)$ galactose.
(b) (+) Lactose is a $\beta$-glycoside formed by the union of a molecule of $D(+)$ glucose and a molecule of $D(+)$ galactose.
(c) (+) Lactose is a reducing sugar and does not exhibit mutarotation.
(d) (+) Lactose, $C _{12} H _{22} O _{11}$ contains $8-OH$ groups.
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Solution:
- (c) All reducing sugar shows mutarotation.
Reducing sugars have hydroxyl group at the anomeric $C 1$ position. In solution, a carbohydrate can open up to its aldehyde form. Hence, it can switch configuration between $\alpha-$ and $\beta-$ forms.
