Which one of the following is absent in eukaryotes

Options

A. Nucleolus
B. Plastids
C. Mesosome
D. Ribosomes

Answer

**Step-by-Step Solution:**

1. **Understand the Question**: The question asks which structure is absent in eukaryotic cells among the given options: nucleolus, plastids, mesosome, and ribosomes.

2. **Analyze the Options**:
- **Nucleolus**: This is a structure found within the nucleus of eukaryotic cells, involved in ribosome production. Therefore, it is present in eukaryotes.
- **Plastids**: These are organelles found in plant cells (which are eukaryotic) and are involved in photosynthesis and storage. Thus, plastids are present in eukaryotes.
- **Mesosome**: This structure refers to the folded invaginations of the plasma membrane found in prokaryotic cells (like bacteria). Mesosomes are not found in eukaryotic cells.
- **Ribosomes**: These are the sites of protein synthesis and are present in both prokaryotic and eukaryotic cells.

3. **Identify the Correct Answer**: Since mesosomes are specifically associated with prokaryotic cells and are absent in eukaryotic cells, the correct answer is mesosome.

4. **Conclusion**: The structure that is absent in eukaryotes is mesosome.

**Final Answer**: Mesosome

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