Uridine present in RNA is

The correct option/answer is: nucleoside

Explanation:
To understand why uridine is classified as a nucleoside, let's break down the composition of nucleic acid components:
1. Nitrogenous Base: These are nitrogen-containing ring molecules. In RNA, the pyrimidine bases are uracil and cytosine, and the purine bases are adenine and guanine. Uracil is the base itself.
2. Nucleoside: A nucleoside is formed when a nitrogenous base is covalently linked to a pentose sugar (ribose in RNA, or deoxyribose in DNA) via a β-N-glycosidic bond. When the nitrogenous base uracil attaches to a ribose sugar, the resulting compound is called uridine. Therefore, uridine is a nucleoside.
3. Nucleotide: A nucleotide is formed when a phosphate group is added to the sugar of a nucleoside (i.e., Nucleoside + Phosphate = Nucleotide). For example, uridine monophosphate (UMP) is a nucleotide, not uridine itself.

Comparing the given options:
- purine: This is a category of nitrogenous bases (adenine and guanine), not a sugar-base compound.
- pyrimidine: This is a category of nitrogenous bases (uracil, cytosine, thymine). Uracil is a pyrimidine base, but uridine includes the sugar group.
- nucleotides: These contain a phosphate group, which uridine lacks.
- nucleoside: This correctly describes uridine, which is composed solely of the uracil base and ribose sugar.