Protein synthesis in an animal cell occurs

Options

A. Only on the ribosomes present in the cytosol
B. Only on ribosomes attached to the nuclear envelope and ER
C. On ribosomes present in the cytoplasm as well as in mitochondria
D. On ribosomes present in the nucleolus as well as in cytoplasm

Answer

**Step-by-Step Solution:**

1. **Understanding Protein Synthesis**: Protein synthesis is the process by which cells generate new proteins. This process occurs primarily on ribosomes, which are the cellular machinery responsible for translating messenger RNA (mRNA) into polypeptide chains (proteins).

2. **Identifying Ribosome Locations**: Ribosomes can be found in various locations within the cell:
- Free ribosomes are located in the cytosol (the fluid part of the cytoplasm).
- Bound ribosomes are attached to the endoplasmic reticulum (ER), specifically the rough ER.
- Ribosomes are also present in mitochondria, which have their own ribosomes for synthesizing some of their proteins.

3. **Evaluating the Options**:
- **Option A**: "Only on ribosomes present in cytosol" - This is incorrect because ribosomes are also found on the rough endoplasmic reticulum and in mitochondria.
- **Option B**: "Only on ribosomes attached to the nuclear envelope and endoplasmic reticulum" - This is incorrect because the nuclear envelope does not contain ribosomes.
- **Option C**: "On ribosomes present in the cytoplasm as well as in mitochondria" - This is correct because ribosomes are indeed found in both the cytoplasm (as free ribosomes or on rough ER) and in mitochondria.
- **Option D**: "On ribosomes present in the nucleus as well as in cytoplasm" - This is incorrect because ribosomes are not present in the nucleus.

4. **Conclusion**: The correct answer is **Option C**: Protein synthesis in an animal cell occurs on ribosomes present in the cytoplasm as well as in mitochondria.

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