# DBT JRF 2020 — Question 2

Exam: DBT JRF 2020 · Section: A · Topic: Biochemistry · Difficulty: Easy

## Question

Which of the following is a non-reducing sugar?

## Options

- **A.** fructose
- **B.** sucrose
- **C.** ribose
- **D.** galactose

## Answer

Option B

## Explanation

A reducing sugar is one that can reduce an oxidising agent (e.g. Fehling's or Benedict's reagent) due to a free anomeric carbon bearing a free aldehyde or ketone group. Sucrose is a NON-reducing sugar because the glycosidic bond links the anomeric C1 of glucose to the anomeric C2 of fructose — both anomeric hydroxyl groups are used in bond formation, so neither reducing end is free. In contrast, fructose (ketone at C2), ribose (aldehyde at C1), and galactose (aldehyde at C1) all retain free anomeric carbons and are reducing sugars.

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