Guanine is an example of

Options

A. a nitrogenous base
B. a nucleoside
C. a nucleotide
D. phosphate

Explanation

To determine what guanine is an example of, we can analyze its structure and classification. Here’s a step-by-step breakdown:

### Step 1: Understand the Structure of Guanine
Guanine is a chemical compound that belongs to a class of molecules known as nitrogenous bases. It contains nitrogen atoms and has a specific molecular structure that includes rings and functional groups.

### Step 2: Identify the Classification of Guanine
Guanine is classified as a nitrogenous base. Nitrogenous bases are the building blocks of nucleic acids (DNA and RNA) and are essential for the storage and transmission of genetic information.

### Step 3: Distinguish Between Related Terms
- **Nucleoside**: A nucleoside consists of a nitrogenous base (like guanine) attached to a sugar molecule (ribose or deoxyribose). Guanine alone does not include the sugar, so it is not a nucleoside.
- **Nucleotide**: A nucleotide includes a nitrogenous base (like guanine), a sugar, and one or more phosphate groups. Guanine by itself does not contain these additional components, so it is not a nucleotide.
- **Phosphate**: Phosphate refers to a specific chemical group (PO4) and is not related to the classification of guanine.

### Conclusion
Based on the analysis, guanine is classified as a nitrogenous base. Therefore, the correct answer to the question "Guanine is an example of" is:

**Answer: Nitrogenous base**

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