Which one of the following structures is an organelle within an organelle
" " Or
Which of the following cell organelle lacks DNA and bounding membrane

Options

A. ER
B. Mesosome
C. Ribosome
D. Peroxisome

Answer

### Step-by-Step Solution

1. **Understanding the Question**: The question asks for a structure that is considered an "organelle within an organelle." This means we are looking for a smaller organelle that exists inside a larger organelle.

2. **Identifying Organelles**: We need to recall the different types of cell organelles. Common organelles include:
- Nucleus
- Mitochondria
- Chloroplasts
- Ribosomes
- Endoplasmic Reticulum (ER)

3. **Analyzing the Options**: Since the question does not provide specific options, we will analyze the known organelles:
- **Ribosomes**: These are small structures that synthesize proteins and can be found either free in the cytoplasm or attached to the endoplasmic reticulum (forming rough ER). They do not have a membrane.
- **Mitochondria and Chloroplasts**: These are organelles that contain their own DNA and have double membranes.
- **Endoplasmic Reticulum**: This is a membranous organelle that serves as a site for protein and lipid synthesis.

4. **Conclusion**: Ribosomes are the only structures that can be considered organelles within organelles, as they are found within the endoplasmic reticulum and do not possess a membrane or DNA.

5. **Final Answer**: Therefore, the correct answer to the question is that ribosomes are organelles within organelles.