Question

RNA is a labile molecule due to the presence of:

• A. 3’-OH group
• B. 5’-OH group
• C. 4’-OH group
• D. 2’-OH group

Answer 1

The Correct Option is D

RNA is considered labile, or chemically unstable, largely due to the presence of the 2’-OH (hydroxyl) group in its ribose sugar. This hydroxyl group is located on the second carbon of the ribose ring, which is a crucial structural difference from DNA, where the second carbon is bonded to a hydrogen atom instead. 

The presence of this 2’-OH group makes RNA more susceptible to hydrolysis. Here's a breakdown of how this occurs:

1. Structure of RNA: RNA consists of a long chain of nucleotides, each comprising a ribose sugar, a phosphate group, and a nitrogenous base.
2. Role of the 2’-OH Group: The 2’-OH group in RNA can form a nucleophilic attack on the adjacent phosphorus atom in the phosphate backbone, which can lead to strand scission.
3. Mechanism of Hydrolysis: In physiological conditions, the 2’-OH can interact with water or other catalysts, leading to the cleavage of the phosphodiester bond. This susceptibility to hydrolysis makes the RNA molecule more unstable compared to DNA.

In conclusion, the presence of the 2’-OH group in the ribose sugar of RNA makes it a more labile molecule, thus differentiating it from DNA, which lacks this hydroxyl group.

Answer 2

RNA is a labile molecule due to the presence of the 2’-OH group. The 2'-OH group on the ribose sugar in RNA makes the molecule more susceptible to hydrolysis, especially under alkaline conditions. This makes RNA more unstable compared to DNA, which lacks the 2’-OH group (replaced by a 2’-H in deoxyribose).

(1) 3’-OH group: The 3’-OH group is necessary for RNA strand elongation during transcription but does not contribute to its instability.

(2) 5’-OH group: The 5’-OH group is involved in the attachment of nucleotides during transcription but does not significantly contribute to the instability of RNA.

(3) 4’-OH group: This does not exist in the context of the ribose sugar structure of RNA or DNA.

(4) 2’-OH group: The 2’-OH group makes RNA highly reactive and more prone to degradation, especially under alkaline conditions.

Thus, the correct answer is (4) 2’-OH group.