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

Options

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

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 break it down step by step.

### Step 1: Understand the Components
The question mentions two components: a sugar and a nitrogenous base. In biochemistry, these components are commonly found in nucleic acids (DNA and RNA).

**Hint:** Identify the basic components of nucleic acids, which include sugars and nitrogenous bases.

### Step 2: Identify the Linkage
The question specifies that the sugar and base are linked by a "beta glycosidic bond." Glycosidic bonds are connections formed between a sugar and another molecule, which in this case is a nitrogenous base.

**Hint:** Recall the types of bonds that can form between sugars and bases in nucleic acids.

### Step 3: Define the Term
A unit that consists of a sugar (either ribose or deoxyribose) and a nitrogenous base (which can be a purine or pyrimidine) linked by a glycosidic bond is known as a **nucleoside**.

**Hint:** Think about the definitions of nucleosides, nucleotides, and other related terms.

### Step 4: Differentiate Between Nucleosides and Nucleotides
While a nucleoside consists of just the sugar and base, a nucleotide includes a phosphate group in addition to the sugar and base. Since the question only refers to the sugar and base, we conclude that it is a nucleoside.

**Hint:** Remember that nucleotides are formed when a phosphate group is added to a nucleoside.

### Conclusion
The correct answer to the question is **nucleoside**.

### Final Answer:
A unit composed of a sugar and base linked by a beta glycosidic bond is known as a **nucleoside**.