The iron in hemoglobin and myoglobincan exist in either the Fe2 or the Fe3 oxidation state.forms 4 coordination bonds with the 4 nitrogen atoms

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Answer

Iron in Hemoglobin and Myoglobin

Iron in Hemoglobin and Myoglobin – Detailed Analysis

✔ Statement 1: Iron is in the Fe²⁺ (ferrous) oxidation state.

This is correct. In both hemoglobin and myoglobin, iron exists in the ferrous (Fe²⁺) state, which is essential for binding oxygen reversibly. Oxidation to Fe³⁺ (ferric state) renders it unable to bind O₂ effectively (as seen in methemoglobin).

✔ Statement 2: Protein coordination bonds with the histidine residues alter the primary structure of the heme and the magnetic field around the iron.

Correct. The proximal histidinedistal histidine

✔ Statement 3: Cellular oxygen delivery is affected by the Fe²⁺ oxidation state.

Absolutely correct. Only Fe²⁺ can bind and release O₂ reversibly. If iron is oxidized to Fe³⁺, as in methemoglobin, it loses its oxygen-carrying ability, severely affecting tissue oxygenation.

✔ Statement 4: Stabilization of the Fe²⁺ state is key to proper environment of the heme-binding site.

Correct. The protein environment (including histidine coordination and the hydrophobic pocket of the heme) stabilizes the Fe²⁺ state. This ensures iron remains in the active oxidation state and prevents autoxidation to Fe³⁺, preserving hemoglobin/myoglobin function.

✅ Correct Answer:

All 1 through 4 are correct.

  • Each statement accurately reflects essential biochemical and structural features of iron in hemoglobin and myoglobin.
  • Iron’s oxidation state and its coordination with histidine residues are fundamental to oxygen transport and delivery.

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