A unit composed of a sugar and base linked by `beta` glycosidic bond is known as a

Options

A. Nucleotide
B. Nucleoside
C. Glycoside
D. Purine

Answer

To solve the question, "A unit composed of a sugar and base linked by a beta glycosidic bond is known as a?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- We need to identify what a unit composed of a sugar and a base means. In biochemistry, a sugar can refer to a pentose sugar, which is commonly found in nucleic acids like DNA and RNA.

2. **Identifying the Bond Type**:
- The question specifies that the sugar and base are linked by a beta glycosidic bond. This type of bond is crucial in the structure of nucleic acids.

3. **Defining the Terms**:
- A sugar (pentose) linked to a nitrogenous base (which can be either a purine or a pyrimidine) forms a specific unit. This unit is known as a **nucleoside**.

4. **Differentiating Between Nucleoside and Nucleotide**:
- It’s important to note that when a phosphate group is added to a nucleoside, it becomes a **nucleotide**. However, since the question only asks for the unit composed of sugar and base, we will focus on the nucleoside.

5. **Final Answer**:
- Therefore, the answer to the question is that a unit composed of a sugar and base linked by a beta glycosidic bond is known as a **nucleoside**.