How many types of cells are known

Options

A. One
B. Two
C. Three
D. Four

Answer

### Step-by-Step Solution:

1. **Identify the Types of Cells**: There are three main types of cells recognized in biology: prokaryotic cells, mesokaryotic cells, and eukaryotic cells.

2. **Prokaryotic Cells**:
- Definition: Prokaryotic cells are primitive cells that do not have a true nucleus.
- Characteristics: The nuclear material is not enclosed by a nuclear membrane.
- Examples: Bacteria and cyanobacteria are common examples of prokaryotic cells.
- Classification: Prokaryotic organisms are classified under the kingdom Monera.

3. **Mesokaryotic Cells**:
- Definition: Mesokaryotic cells exhibit intermediate characteristics between prokaryotic and eukaryotic cells.
- Characteristics: These cells have a nuclear membrane, but their DNA does not contain histone proteins.
- Examples: Dinoflagellates are an example of mesokaryotic cells.

4. **Eukaryotic Cells**:
- Definition: Eukaryotic cells are more advanced and complex than prokaryotic cells.
- Characteristics: They possess a true nucleus that is enclosed by a nuclear membrane and contain histone proteins.
- Examples: Organisms in the kingdoms Protista, Plantae, and Animalia are composed of eukaryotic cells.

5. **Conclusion**: Based on the classification, the three types of cells known are prokaryotic, mesokaryotic, and eukaryotic cells.

### Final Answer:
The known types of cells are three: prokaryotic cells, mesokaryotic cells, and eukaryotic cells.

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