A nitrogen base is linked to sugar by a glycosidic bond at carbon number

Options

A. 1'
B. 2'
C. 4'
D. 5'

Answer

To answer the question regarding which carbon number of the sugar is linked to the nitrogen base by a glycosidic bond, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components of a Nucleotide**:
A nucleotide consists of three main components: a nitrogenous base, a sugar (which can be ribose or deoxyribose), and a phosphate group.

2. **Understand the Structure of the Sugar**:
In this case, we are dealing with deoxyribose sugar, which is a pentose sugar (5 carbon atoms).

3. **Locate the Carbon Atoms**:
The carbon atoms in deoxyribose are numbered as follows:
- Carbon 1 (C1)
- Carbon 2 (C2)
- Carbon 3 (C3)
- Carbon 4 (C4)
- Carbon 5 (C5)

4. **Identify the Nitrogenous Base**:
The nitrogenous base can be either a purine or a pyrimidine. In the context of DNA, the nitrogenous bases are adenine, guanine, cytosine, and thymine.

5. **Determine the Bonding Position**:
The nitrogenous base is attached to the sugar through a glycosidic bond. This bond specifically forms between the nitrogen atom of the base and the carbon atom of the sugar.

6. **Identify the Specific Carbon Number**:
For deoxyribose sugar, the nitrogenous base is linked to the sugar at Carbon 1 (C1). The nitrogen atom involved in this bond is typically at the 9th position in purines (like adenine and guanine) or at the 1st position in pyrimidines (like cytosine and thymine).

7. **Conclusion**:
Therefore, the nitrogen base is linked to the sugar by a glycosidic bond at Carbon number 1.

### Final Answer:
The nitrogen base is linked to the sugar by a glycosidic bond at carbon number **1**.

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