Question

Which one of the following statements regarding pyrimidine nucleotide is TRUE?

• A. The base of the nucleotide is joined covalently at N-3 of pyrimidine to the first carbon of the Pentose.
• B. The base of the nucleotide is joined covalently at N-3 of purine to the first carbon of the pentose.
• C. The base of the nucleotide is joined covalently at N-1 of pyrimidine to the first carbon of the pentose.
• D. The base of the nucleotide is joined covalently at N-1 of purine to the first carbon of the pentose.

Hint:

To remember glycosidic bond linkages:
- Pyrimidines: N-1 connected to C-1' of the sugar.
- Purines: N-9 connected to C-1' of the sugar.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Nucleotides are the structural subunits of nucleic acids (DNA and RNA). They consist of a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Step 2: Detailed Explanation:
1. The linkage between the nitrogenous base and the pentose sugar is a covalent \(\beta\)-N-glycosidic bond.
2. In pyrimidine nucleotides (cytosine, thymine, and uracil), this glycosidic bond forms between the N-1 nitrogen of the single-ring pyrimidine base and the C-1' carbon of the pentose sugar.
3. In purine nucleotides (adenine and guanine), the glycosidic bond forms between the N-9 nitrogen of the double-ring purine base and the C-1' carbon of the sugar.
4. Therefore, statement C is the correct description of a pyrimidine nucleotide.

Step 3: Final Answer:
The pyrimidine base is covalently linked to the C-1' carbon of the pentose sugar via its N-1 nitrogen.