Which mineral is required for oxygen transport in the blood and can act as both an electron donor and acceptor?

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

Answer: (A)

Oxygen transport in the blood relies on a metal in the heme part of hemoglobin that can switch oxidation states. In the heme group, iron is in the Fe2+ state and binds oxygen, forming oxyhemoglobin so oxygen can be carried from the lungs to tissues. When oxygen is released, the iron returns to its usable state, ready to bind more oxygen. Iron’s ability to alternate between different oxidation states also makes it a versatile electron carrier in many biochemical reactions, meaning it can both accept and donate electrons as needed by metabolic processes. Other minerals like sodium, calcium, and phosphorus are essential for many bodily functions, but they don’t play this role in oxygen transport via hemoglobin. That combination of binding oxygen and participating in redox chemistry points to iron as the mineral in question.