Which pairing is correct?

• A. Iron — Immune function
• B. Magnesium — Oxygen delivery
• C. Magnesium — ATP production
• D. Iron — ATP production

Answer: (C)

Energy production in cells relies on mineral cofactors that enable ATP formation. Magnesium is essential because ATP actually functions in cells as a complex with Mg2+. The magnesium ion stabilizes the negative charges on the phosphate groups and enables the phosphorylation steps that enzymes perform in glycolysis, the Krebs cycle, and the electron transport chain. Without enough magnesium, many ATP‑dependent reactions slow down, so energy production drops. That direct role makes magnesium paired with ATP production the best match.

Iron is crucial for oxygen transport in hemoglobin and also serves in some components of the electron transport chain, but its most direct, widely taught link is to oxygen delivery, not to ATP production.