The element that is not very mobile and remains fixed to mitochondria and chloroplasts is

Options

A. potassium
B. calcium
C. sulphur
D. iron

Answer

To determine which element is not very mobile and remains fixed to mitochondria and chloroplasts, we can analyze the given options: potassium, calcium, sulfur, and iron.

### Step-by-Step Solution:

1. **Understanding Element Mobility**:
- In plants, certain elements are more mobile than others. Mobile elements can move easily within the plant, while immobile elements tend to stay fixed in specific locations.

2. **Analyzing Each Option**:
- **Potassium**: This element is known to be mobile in plants, as it can move to areas where it is needed.
- **Calcium**: Calcium is often found in the form of calcium pectate in cell walls and is tightly bound to the middle lamella, making it immobile.
- **Sulfur**: Sulfur is also relatively mobile and can move within the plant.
- **Iron**: Iron is generally less mobile than potassium and sulfur but can still move to some extent.

3. **Identifying the Immobile Element**:
- From the analysis, calcium is the element that is not very mobile. It remains fixed to structures like mitochondria and chloroplasts due to its role in forming calcium pectate in cell walls.

4. **Conclusion**:
- Therefore, the element that is not very mobile and remains fixed to mitochondria and chloroplasts is **calcium**.

### Final Answer:
The element that is not very mobile and remains fixed to mitochondria and chloroplasts is **calcium**.

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