A base sugar phosphate' unit in nucleic acid is known as

Options

A. nucleotide
B. nucleoside
C. phosphotide
D. polypeptide

Explanation

To solve the question "A base sugar phosphate unit in nucleic acid is known as," we need to identify the correct term that describes this unit. Let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Components**:
- A nucleic acid is made up of units that consist of three main components: a nitrogenous base, a sugar, and a phosphate group.

2. **Identifying the Units**:
- The nitrogenous base can be adenine, thymine, cytosine, or guanine (in DNA) or adenine, uracil, cytosine, or guanine (in RNA).
- The sugar can either be ribose (in RNA) or deoxyribose (in DNA).
- The phosphate group is a molecule consisting of phosphorus and oxygen.

3. **Combining the Components**:
- When these three components (nitrogenous base, sugar, and phosphate group) are combined, they form a single unit known as a nucleotide.

4. **Evaluating the Options**:
- A. Nucleotide - This is the correct answer as it refers to the base sugar phosphate unit in nucleic acids.
- B. Nucleoside - This term refers to the base and sugar only, without the phosphate group.
- C. Phosphatide - This is not a term used in the context of nucleic acids.
- D. Polypeptide - This refers to a chain of amino acids, not nucleic acids.

5. **Conclusion**:
- Therefore, the answer to the question is **A. Nucleotide**.

### Final Answer:
A base sugar phosphate unit in nucleic acid is known as a **nucleotide**.