Question

The carbohydrates “Ribose” present in DNA is 
A. A pentose sugar 
B. Present in pyranose form 
C. In “D” configuration 
D. A reducing sugar, when free 
E. In \( \alpha \)-anomeric form

• A. A, C and D Only
• B. A, B and E Only
• C. B, D and E Only
• D. A, D and E Only

Hint:

Ribose in DNA exists in the D-configuration and as a pentose sugar. It is a reducing sugar when free and typically forms a furanose ring, not a pyranose ring.

Answer 1

The Correct Option is A

Let's analyze each statement: 
- A: A pentose sugar Ribose is indeed a pentose sugar, as it contains five carbon atoms. So, A is true.
- B: Present in pyranose form Ribose in DNA exists primarily in its furanose form (a 5-membered ring) rather than the pyranose form (a 6-membered ring). Therefore, B is false.
- C: In “D” configuration Ribose is found in the D-configuration, as it is derived from D-galactose. So, C is true.
- D: A reducing sugar, when free Ribose is a reducing sugar when it is not part of a nucleotide or when it is in its free form. Therefore, D is true.
- E: In \( \alpha \)-anomeric form Ribose can exist in both \( \alpha \)- and \( \beta \)-anomeric forms, depending on the position of the hydroxyl group at the anomeric carbon. Thus, E is not always true.
Therefore, the correct answer is (1) A, C, and D only.