Name the element at the centre of a chlorophyll molecule.

• A. Magnesium
• B. Iron
• C. Calcium
• D. Sodium

Answer: (A)

Chlorophyll is a metalloporphyrin, a large ring structure with a metal ion sitting right at its center. In plants, that central metal is magnesium. The ring coordinates to four nitrogen atoms in the porphyrin core, which helps keep the ring flat and stabilizes the conjugated system that absorbs light for photosynthesis. This Mg center is specific to chlorophyll and different from other heme-containing molecules, where iron sits in the center. Calcium and sodium aren’t the central metals in chlorophyll, so the element at the center is magnesium.