Question

Reflect and Apply Why is RNA more vulnerable to alkaline hydrolysis than DNA?

Short answer

RNA's 2' hydroxyl group makes it prone to alkaline hydrolysis, while DNA lacks this group and is more stable.

Step-by-step solution

Identify the structural difference

Recognize that RNA has a ribose sugar, while DNA has a deoxyribose sugar. The key difference is that ribose has a hydroxyl group (-OH) on the 2' carbon.

Understand vulnerability

Alkaline hydrolysis in basic conditions can cause the hydroxyl group on the RNA's 2' carbon to attack the phosphate backbone, leading to cleavage of the RNA chain.

Compare with DNA

DNA lacks the 2' hydroxyl group, having a hydrogen instead. This absence prevents intramolecular attacks, making DNA more resistant to alkaline hydrolysis.

Conclusion

Since RNA has the 2' hydroxyl group, it is more likely to undergo alkaline hydrolysis, while DNA's structural difference makes it less vulnerable.

Key concepts

RNA structure

RNA stands for Ribonucleic Acid. It is a crucial molecule in the coding, decoding, regulation, and expression of genes.
Its structure consists of a ribose sugar, which is a five-carbon sugar contributing to its backbone.
One key structural feature of RNA is the presence of a hydroxyl group (-OH) on the 2' carbon of the ribose sugar.
This additional hydroxyl group differentiates RNA from DNA and plays a significant role in its stability and reactivity.
RNA also includes nitrogenous bases (adenine, guanine, cytosine, and uracil) that pair complementarily with DNA during processes like transcription.
However, unlike DNA, RNA is usually single-stranded and can form complex three-dimensional shapes by folding upon itself. These structures enable it to perform various functions within the cell.
While this versatility is beneficial, RNA’s structure also makes it more susceptible to certain chemical reactions, such as alkaline hydrolysis.

DNA structure

DNA stands for Deoxyribonucleic Acid. It is the hereditary material in humans and almost all other organisms.
DNA's structure consists of two strands that coil around each other to form a double helix.
The backbone of each strand is made up of a sugar-phosphate chain. The sugar in DNA is deoxyribose, which lacks a hydroxyl group on the 2' carbon, having a hydrogen atom instead.
DNA uses four nitrogenous bases (adenine, guanine, cytosine, and thymine) that pair complementarily to stabilize the double-helix structure.
This pairing is specific: adenine pairs with thymine, and cytosine pairs with guanine, forming base pairs held together by hydrogen bonds.
The double-helix configuration and the absence of the 2' hydroxyl group in DNA make it more chemically stable compared to RNA.
This stability is vital for its role in storing and transmitting genetic information across generations.

alkaline hydrolysis

Alkaline hydrolysis is a chemical reaction where a molecule is broken down by the addition of water in a basic (alkaline) environment.
In the context of RNA and DNA, alkaline hydrolysis can affect their stability and integrity.
For RNA, the hydroxyl group on the 2' carbon is highly reactive under alkaline conditions.
This -OH group can attack the adjacent phosphate backbone within the RNA chain, causing the RNA to break apart or cleave.
DNA, on the other hand, lacks this 2' hydroxyl group, making it more resistant to such reactions.
The absence of the highly reactive hydroxyl group on deoxyribose means that DNA does not undergo this type of cleavage under alkaline conditions.
Thus, DNA's structural composition contributes significantly to its chemical stability and longevity.