1″ carbon of pentose sugar of nucleic acid joins –
## **Core Concept**
The question tests understanding of nucleic acid structure, specifically the linkage between the pentose sugar and other components in nucleic acids. Nucleic acids, including DNA and RNA, are composed of nucleotides, each containing a pentose sugar (**ribose** in RNA and **deoxyribose** in DNA), a phosphate group, and a nitrogenous base.
## **Why the Correct Answer is Right**
The correct answer, **B. N-glycosidic bond**, is right because the 1' carbon of the pentose sugar in a nucleotide is linked to a nitrogenous base through an **N-glycosidic bond**. This bond is formed between the 1' carbon of the pentose sugar and a nitrogen atom on the nitrogenous base. In purines (adenine and guanine), this bond forms with the N9 atom, and in pyrimidines (cytosine, thymine, and uracil), it forms with the N1 atom.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Phosphodiester bond - This is incorrect because phosphodiester bonds link the 5' carbon of one pentose sugar to the 3' carbon of another, forming the backbone of the nucleic acid, not the bond between the pentose sugar and the nitrogenous base.
- **Option C:** Hydrogen bond - This is incorrect because hydrogen bonds are responsible for holding the two strands of DNA (or RNA) together, specifically between the nitrogenous bases, not for linking the sugar to the base within a nucleotide.
- **Option D:** Peptide bond - This is incorrect because peptide bonds are found in proteins, linking amino acids together, and have no role in nucleic acid structure.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **N-glycosidic bond** is crucial for the stability and function of nucleic acids. Damage to this bond can lead to issues with DNA and RNA function, potentially leading to various diseases.
## **Correct Answer:** B. N-glycosidic bond.