A 65-year-old male with a history of chronic obstructive pulmonary disease (COPD) is admitted with worsening cyanosis and shortness of breath. His arterial blood gas shows severe hypoxemia, and methemoglobinemia is suspected due to nitrate exposure from contaminated water. The physician notes that the iron in his hemoglobin is not functioning properly. What is the primary physiologic consequence of iron (Fe) oxidation from Fe²⁺ to Fe³⁺ in hemoglobin, as seen in methemoglobinemia?
