Question

Why is RNA more vulnerable to alkaline hydrolysis than DNA?

Short answer

RNA is more vulnerable to alkaline hydrolysis because it has a 2' hydroxyl group that can react and break the phosphodiester bond under alkaline conditions.

Step-by-step solution

Identify the structural difference

Both RNA and DNA are nucleic acids, but they differ in their sugar components. RNA contains ribose sugar, while DNA contains deoxyribose sugar.

Analyze the presence of the hydroxyl group

Ribose in RNA has a hydroxyl group (-OH) attached to the 2' carbon atom, whereas deoxyribose in DNA lacks this hydroxyl group at the same position (it has only a hydrogen atom instead).

Understand the reaction with alkaline conditions

The 2' hydroxyl group in RNA makes it more reactive under alkaline conditions. When the environment becomes alkaline, the -OH group can act as a nucleophile and lead to the breaking of the phosphodiester bond in the RNA strand, resulting in hydrolysis.

Compare the stability

In DNA, the 2' hydrogen does not participate in such reactions, making DNA more stable and less susceptible to alkaline hydrolysis compared to RNA.

Conclude the reason

Thus, the presence of the 2' hydroxyl group in the ribose sugar of RNA is the main reason for its higher vulnerability to alkaline hydrolysis compared to DNA.

Key concepts

RNA structure

RNA, or ribonucleic acid, plays crucial roles in the coding, decoding, regulation, and expression of genes. It typically forms a single-stranded nucleotide chain. Each nucleotide in RNA is composed of a ribose sugar, nitrogenous bases (adenine, uracil, cytosine, and guanine), and a phosphate group. The ribose sugar is notable for its hydroxyl group (-OH) on the 2' carbon atom. This feature makes RNA more chemically active and less stable when compared to DNA. Additionally, RNA structures can form various shapes, such as loops and helices, due to intra-molecular base pairing.

DNA structure

DNA, or deoxyribonucleic acid, is the molecule responsible for storing and transmitting genetic information in living organisms. Unlike RNA, DNA is typically double-stranded, forming a double helix shape. Each nucleotide in DNA includes a deoxyribose sugar, nitrogenous bases (adenine, thymine, cytosine, and guanine), and a phosphate group. The deoxyribose sugar lacks a hydroxyl group at the 2' carbon position, having only a hydrogen atom instead. This absence of the 2' -OH group helps to stabilize DNA, making it less reactive and more resistant to chemical degradation. The complementary base pairing (adenine with thymine, cytosine with guanine) across the two strands makes the DNA molecule very stable.

Alkaline hydrolysis

Alkaline hydrolysis is a reaction where RNA breaks down in the presence of a basic (alkaline) environment. Alkaline substances have a high pH and a surplus of hydroxide ions (OH-). In RNA, the 2' hydroxyl group on the ribose sugar becomes more reactive in these conditions. This -OH group can attack and break the phosphodiester bonds between nucleotides, leading to the cleavage of the RNA chain. As a result, RNA degrades rapidly in alkaline environments. In contrast, DNA, which lacks the 2' -OH group, remains stable under the same conditions.

2' hydroxyl group

The 2' hydroxyl group is a chemical group (-OH) attached to the second carbon atom of the ribose sugar in RNA. This hydroxyl group is not present in the deoxyribose sugar of DNA, which instead has a hydrogen atom (H) at the same position. The presence of the 2' hydroxyl group makes RNA more susceptible to chemical reactions, particularly under alkaline conditions. The hydroxyl group can act as a nucleophile, attacking the phosphodiester bond within RNA and causing it to break. This reactivity is a key reason why RNA is less stable and more prone to degradation than DNA.

Phosphodiester bond stability

Phosphodiester bonds are the linkages between nucleotides in DNA and RNA. In RNA, these bonds are more vulnerable to breaking under alkaline conditions due to the presence of the 2' hydroxyl group. When the hydroxyl group attacks the phosphodiester bond, it leads to cleavage and fragmentation of the RNA strand. In DNA, the absence of the 2' -OH group makes these bonds significantly more stable and less prone to hydrolysis. This stability is crucial for the long-term storage of genetic information in DNA, ensuring it can withstand various chemical environments without degrading.