Nucleic Acid Pentose—Identify the Sugar (RNA Focus) Within nucleic acids, which pentose sugar is characteristic of RNA and forms a major component of its backbone (contrast with DNA, which contains deoxyribose)?

Introduction / Context:Nucleic acids are polymers of nucleotides composed of a nitrogenous base, a pentose sugar, and phosphate. RNA uses ribose, whereas DNA uses 2′-deoxyribose. Identifying the correct sugar clarifies structural differences that influence stability, catalysis, and function (e.g., RNA’s 2′-OH enables diverse structures and ribozyme activity).

Given Data / Assumptions:

• RNA = ribonucleic acid → ribose sugar.
• DNA = deoxyribonucleic acid → 2′-deoxyribose sugar.
• Other listed sugars are not pentoses used in nucleic acid backbones.

Concept / Approach:Map names to sugars: “ribo-” and “deoxyribo-” denote ribose and deoxyribose. Ribose’s additional 2′-OH affects backbone chemistry (greater susceptibility to alkaline hydrolysis and increased conformational freedom), explaining many biological differences between DNA and RNA. Therefore, for RNA specifically, the pentose is ribose.

Step-by-Step Solution:

Verification / Alternative check:Chemical analysis and classic hydrolysis reactions differentiate RNA (sensitive to base due to 2′-OH) from DNA, confirming the sugar identity.

Why Other Options Are Wrong:

• Galactose/mannose: hexoses used in glycans, not nucleic acids.
• Maltose: a disaccharide, not a nucleotide sugar.
• Deoxyribose: correct for DNA, not RNA.

Common Pitfalls:Assuming “nucleic acids” implies only DNA; the question specifies RNA to avoid ambiguity.

Final Answer:Ribose