Differentiate between reducing and non-reducing sugars.

Explanation

All those carbohydrates which reduce Fehling.s solution to red ppt. of `Cu_2 O` and Tollen.s reagent to metallic silver are referred to as reducing sugars. On the other hand carbohydrates which ao not give these tests are called non-reducing sugars.
All monosaccharides, whether aldose or ketose are reducing sugars. In an aldose the-CHO group present reduces the Fehling.s solution and Tolled.s reagent. It is believed that under the reaction conditions (i.e., alkaline medium), a ketose is converted into a aldose which reduces the Fehling.s solution and Tollen.s reagent.