Which of the following structures is not found in a prokaryotic cell?

Options

A. Nuclear envelope
B. ribosomes
C. Mesosome
D. Plasma membrane

Answer

To determine which structure is not found in a prokaryotic cell, we need to understand the characteristics of prokaryotic cells and their components.

### Step-by-Step Solution:

1. **Identify Prokaryotic Cells**: Prokaryotic cells are simple, unicellular organisms that lack a nucleus and membrane-bound organelles. They include bacteria and archaea.

2. **Key Features of Prokaryotic Cells**:
- **Cell Wall**: Prokaryotic cells have a rigid cell wall that provides structure and protection.
- **Plasma Membrane**: They possess a plasma membrane that controls the movement of substances in and out of the cell.
- **Cytoplasm**: The interior of the cell is filled with cytoplasm where metabolic processes occur.
- **Ribosomes**: Prokaryotic cells contain ribosomes for protein synthesis, although they are smaller than those found in eukaryotic cells.
- **DNA**: The genetic material is present as a single, circular strand of DNA that is not enclosed within a nuclear membrane (nuclear envelope).

3. **Structures Typically Absent in Prokaryotic Cells**:
- **Nuclear Envelope**: Prokaryotic cells do not have a nuclear envelope; their DNA is not enclosed in a nucleus.
- **Membrane-bound Organelles**: Structures such as mitochondria, endoplasmic reticulum, and Golgi apparatus are absent in prokaryotic cells.

4. **Conclusion**: Based on the above characteristics, the structure that is not found in prokaryotic cells is the **nuclear envelope**.

### Final Answer:
The structure that is not found in a prokaryotic cell is the **nuclear envelope**.

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