Which mineral is primarily responsible for oxygen transport in the blood?

• A. Potassium
• B. Chloride
• C. Iron
• D. Calcium

Answer: (C)

Oxygen transport in the blood is carried mainly by hemoglobin in red blood cells, which contains iron in its heme groups. The iron atom in each heme binds one molecule of oxygen, and with four heme sites on each hemoglobin, one molecule of hemoglobin can carry up to four oxygen molecules. This reversible binding allows oxygen to pick up in the lungs and release in tissues where it’s needed. Iron’s role is central because its ferrous form (Fe2+) is the state that binds oxygen.

Potassium, chloride, and calcium have important roles in other bodily processes—potassium in cellular function and nerve signaling, chloride in acid-base balance and fluid relationships, and calcium in bone structure and signaling—but they do not serve as the primary carriers for oxygen in the bloodstream.