Final answer:
Copper-containing enzymes facilitate the oxidation of ferrous iron, resulting in the formation of ferric iron. This involves an increase in the oxidation state of iron from +2 in ferrous iron to +3 in ferric iron.
Step-by-step explanation:
Copper-containing enzymes catalyze the oxidation of ferrous iron (Fe2+) to ferric iron (Fe3+). This is a redox reaction where the oxidation state of iron increases from +2 to +3. In chemical reactions like the reaction between iron and copper(II) sulfate (CuSO4), iron displaces copper due to its more reactive nature, forming iron(II) sulfate (FeSO4) and elemental copper. This supports the fact that in the presence of copper-containing enzymes, ferrous iron is oxidized to ferric iron, not to a compound like ferrous oxide, ferrous sulfate, or ferrous chloride.