Which metal ion is central in chlorophyll?

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

Answer: (B)

Chlorophyll contains a porphyrin-like ring that binds a metal ion at its center. That central ion stabilizes the ring’s shape and keeps the extended conjugated system intact, which is essential for absorbing visible light efficiently. In chlorophyll, the metal is magnesium. It sits in the middle of the ring coordinated by the four nitrogen atoms of the ring, helping to maintain planarity and the electron-delocalized structure needed for light capture and energy transfer in photosynthesis. Iron is the metal central to heme in hemoproteins, not chlorophyll, which is why it isn’t the correct central ion here. Zinc and copper serve different roles in biology and are not the central ion in chlorophyll either.