Which is wall -less and smallest living cell

Options

A. Algae
B. Bacteriophage
C. Cyanobacteria
D. Mycoplasma

Answer

### Step-by-Step Solution:

1. **Identify the Options**: The question provides four options: algae, bacteriophage, cyanobacteria, and mycoplasm. We need to determine which of these is wall-less and the smallest living cell.

2. **Analyze Each Option**:
- **Algae**: Algae are eukaryotic organisms that possess a cell wall. Therefore, they cannot be the answer.
- **Bacteriophage**: Bacteriophages are viruses that infect bacteria. They are not considered living cells, as they cannot reproduce independently. Thus, this option is also not valid.
- **Cyanobacteria**: Cyanobacteria, also known as blue-green algae, are prokaryotic and have a cell wall. Hence, they do not fit the criteria of being wall-less.
- **Mycoplasm**: Mycoplasm, also known as PPLO (Pleuro-Pneumonia Like Organism), is known to be the smallest living cell and is unique because it lacks a cell wall.

3. **Confirm Characteristics of Mycoplasm**:
- Mycoplasm has a size of approximately 0.0001 meters, making it extremely small.
- It is resistant to antibiotics that target cell wall synthesis, such as penicillin, due to the absence of a cell wall.

4. **Conclusion**: Based on the analysis, the smallest living cell that is wall-less is **mycoplasm**.

### Final Answer:
The smallest living cell that is wall-less is **mycoplasm**.

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