Question

In which of the following is iron in the heme group in the Fe3+ (ferric) state?'

• A. Oxyhaemoglobin
• B. Methaemoglobin
• C. Carbaminohemoglobin
• D. Haemoglobin without oxygen

Answer 1

Answer: (B)

Methaemoglobin

A) Oxyhemoglobin is formed during respiration when oxygen binds to the heme component of the protein haemoglobin in red blood cells. The iron in the heme group is in the ${Fe}^{2+}$ (ferrous) state.

B) Methaemoglobin a stable oxidized form of haemoglobin which is unable to release oxygen to the tissues, produced in some inherited abnormalities and by oxidizing drugs. Iron in the heme group is in the ${Fe}^{3+}$ (ferric) state, not the ${Fe}^{2+}$ (ferrous) of normal hemoglobin.

C) Carbaminohaemoglobin is a compound of hemoglobin and carbon dioxide, and is one of the forms in which carbon dioxide exists in the blood. The iron in the heme group is in the ${Fe}^{2+}$ (ferrous) state.

D) The oxidation of haemoglobin without oxygen is in the ${Fe}^{2+}$ state.

So the correct answer is 'Methaemoglobin'.