Which parts of a cell contain ribosomes ?
I. Chloroplast
II. Mitochondrion
III. Nucleus
IV. Cytoplasm

Options

A. I,II , III and IV
B. I,II and III only
C. I,II and IV only
D. III and IV only

Answer

To determine which parts of a cell contain ribosomes, we will analyze each option provided in the question:

1. **Chloroplast**:
- Chloroplasts are organelles found in plant cells that are responsible for photosynthesis. They contain their own ribosomes, which are of the 70S type, similar to those found in prokaryotes. These ribosomes are involved in synthesizing proteins necessary for the chloroplast's function.
- **Conclusion**: Chloroplasts contain ribosomes.

2. **Mitochondrion**:
- Mitochondria are known as the powerhouses of the cell, generating ATP through cellular respiration. Like chloroplasts, mitochondria also contain 70S ribosomes. These ribosomes are involved in the synthesis of proteins required for the mitochondrion's function.
- **Conclusion**: Mitochondria contain ribosomes.

3. **Nucleus**:
- The nucleus is the control center of the cell, housing the cell's DNA. While ribosomes are not directly present in the nucleus, the nucleolus (a sub-structure within the nucleus) is where ribosomal RNA (rRNA) is synthesized and combined with proteins to form ribosomal subunits. These subunits are then transported to the cytoplasm where they assemble into functional ribosomes.
- **Conclusion**: The nucleus directs the synthesis of ribosomes, but does not contain functional ribosomes itself.

4. **Cytoplasm**:
- The cytoplasm is the gel-like substance within the cell membrane that contains various organelles. Ribosomes can be found freely floating in the cytoplasm or attached to the endoplasmic reticulum (ER). These ribosomes are responsible for translating mRNA into proteins.
- **Conclusion**: The cytoplasm contains ribosomes.

**Final Assessment**:
- Chloroplasts (I) contain ribosomes.
- Mitochondria (II) contain ribosomes.
- Nucleus (III) does not contain functional ribosomes but is involved in their synthesis.
- Cytoplasm (IV) contains ribosomes.

Thus, the correct answer is that ribosomes are found in **Chloroplasts, Mitochondria, and Cytoplasm**. The nucleus is involved in ribosome synthesis but does not contain ribosomes itself.

### Summary of Findings:
- **I. Chloroplast**: Yes, contains ribosomes.
- **II. Mitochondrion**: Yes, contains ribosomes.
- **III. Nucleus**: No functional ribosomes, but synthesizes them.
- **IV. Cytoplasm**: Yes, contains ribosomes.