In multicullular organisms , 70 S ribosomes occur inside

Options

A. Nucleus
B. Mitochondria
C. Lysosome
D. E.R.

Answer

### Step-by-Step Solution:

1. **Understanding Ribosome Types**:
- Ribosomes are essential cellular structures responsible for protein synthesis. They are classified into two types based on their sedimentation rate: 70S and 80S ribosomes.

2. **Identifying Organism Types**:
- Multicellular organisms are typically eukaryotic, which means they have complex cells with membrane-bound organelles.

3. **Ribosome Distribution in Eukaryotes**:
- In eukaryotic cells, the predominant ribosome type found in the cytoplasm is the 80S ribosome. This is crucial for general protein synthesis in the cell.

4. **Presence of 70S Ribosomes**:
- However, 70S ribosomes are also present in eukaryotic cells, specifically within certain organelles that have their own DNA. These organelles include mitochondria and chloroplasts.

5. **Comparison with Prokaryotes**:
- Prokaryotic organisms, such as bacteria, exclusively contain 70S ribosomes. This similarity in ribosome type between mitochondria and prokaryotes supports the endosymbiotic theory, which suggests that mitochondria originated from ancestral prokaryotic cells.

6. **Conclusion**:
- Therefore, in multicellular organisms, 70S ribosomes occur inside mitochondria, which are the organelles responsible for energy production.