70S type of ribosomes are found in

Options

A. prokaryotic cells only
B. prokaryotic cells, chloroplasts and mitochondria
C. mitochondria only
D. nucleus, mitochondria

Answer

**Step-by-Step Solution:**

1. **Understanding Ribosomes**: Ribosomes are cellular structures responsible for protein synthesis. They can be found in both prokaryotic and eukaryotic cells.

2. **Types of Ribosomes**: There are two main types of ribosomes based on their sedimentation coefficients:
- **70S Ribosomes**: Found in prokaryotic cells and in some organelles of eukaryotic cells (like mitochondria and chloroplasts).
- **80S Ribosomes**: Found in the cytoplasm of eukaryotic cells.

3. **Structure of 70S Ribosomes**: The 70S ribosome is composed of two subunits:
- A large subunit (50S)
- A small subunit (30S)

4. **Location of 70S Ribosomes**:
- **Prokaryotic Cells**: All prokaryotic cells (like bacteria) contain 70S ribosomes.
- **Eukaryotic Organelles**: Chloroplasts and mitochondria, which are semi-autonomous organelles in eukaryotic cells, also contain 70S ribosomes. This is because they have their own DNA and machinery for protein synthesis similar to prokaryotes.

5. **Conclusion**: Therefore, the 70S type of ribosomes can be found in:
- Prokaryotic cells
- Chloroplasts
- Mitochondria

**Final Answer**: 70S type of ribosomes are found in prokaryotic cells, chloroplasts, and mitochondria.

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