Which metal ion is a constituent of chlorophyll?

Options

A. Iron
B. Copper
C. Magnesium
D. Zinc

Answer

To determine which metal ion is a constituent of chlorophyll, let's analyze the options provided step by step:

1. **Understanding Chlorophyll**:
- Chlorophyll is a green pigment found in plants that is essential for photosynthesis. It captures light energy, which is then used to convert carbon dioxide and water into glucose and oxygen.

2. **Evaluating the Options**:
- **Option 1: Iron (Fe)**:
- Iron is an important element in many biological processes, especially in hemoglobin in blood. However, it is not a component of chlorophyll.
- **Option 2: Copper (Cu)**:
- Copper plays a role in various plant functions, including lignin synthesis and enzyme activity, but it is not a constituent of chlorophyll.
- **Option 3: Magnesium (Mg)**:
- Magnesium is a crucial component of chlorophyll. It is located at the center of the chlorophyll molecule and is essential for its function in photosynthesis.
- **Option 4: Zinc (Zn)**:
- Zinc is necessary for various plant processes and is involved in the synthesis of certain proteins. However, it is not a part of the chlorophyll molecule.

3. **Conclusion**:
- Based on the analysis of the options, the correct answer is **Magnesium (Mg)**, as it is the metal ion that constitutes chlorophyll.

### Final Answer:
The metal ion that is a constituent of chlorophyll is **Magnesium (Mg)**.