Magnesium is important because it is present in

Options

A. cell membranes
B. chlorophyll molecule
C. haemoglobin molecule
D. bones

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why magnesium is important and in which of the given options it is present.

2. **Evaluating the Options**:
- **Option 1: Cell Membrane**: The cell membrane is primarily composed of a lipid bilayer and proteins. It does not contain magnesium as a significant component. Therefore, this option is incorrect.

- **Option 2: Chlorophyll Molecule**: Chlorophyll is a pigment found in plants that is essential for photosynthesis. It contains a magnesium ion at its center, which is crucial for its function. This makes this option correct.

- **Option 3: Hemoglobin Molecule**: Hemoglobin is a protein in red blood cells that carries oxygen. It primarily contains iron, not magnesium. Thus, this option is also incorrect.

- **Option 4: Bones**: While bones do contain magnesium, they are predominantly composed of calcium. Therefore, this option is not the best answer when considering the importance of magnesium.

3. **Conclusion**: The most significant presence of magnesium is in the chlorophyll molecule, making it the correct answer.

**Final Answer**: Magnesium is important because it is present in the chlorophyll molecule.

---