What is nucleoside? When does it become nucleotide?

Explanation

### Step-by-Step Solution:

1. **Definition of Nucleoside**:
A nucleoside is a molecular structure that consists of two main components: a nitrogenous base and a five-carbon sugar (carbohydrate). The nitrogenous base can be one of the following: adenine, guanine, cytosine, or thymine (in DNA) or uracil (in RNA). The sugar can be either ribose (in RNA) or deoxyribose (in DNA).

2. **Components of Nucleoside**:
- **Nitrogenous Base**: This can be purines (adenine and guanine) or pyrimidines (cytosine, thymine, and uracil).
- **Five-Carbon Sugar**: This is either ribose (with an -OH group on the 2' carbon) or deoxyribose (with an -H on the 2' carbon).
...