Question

In which state iron is present in haemoglobin?
A) Fe
B) $Fe^{2+}$
C) $Fe^{2+}$
D) None of the above.

Answer 1

Hint: RBC is a biconcave cell that transports oxygen to different parts of the body. Mature RBCs are devoid of cell organelles and contain the cytoplasm only, which gives more surface area for oxygen to bind. Haemoglobin is a red coloured iron-containing complex protein.

Complete answer: Erythrocytes or RBCs are blood cells formed in the red bone marrow in adults. They are biconcave, circular and devoid of the nucleus. Mature mammalian RBCs are devoid of cell organelles and almost the entire cytoplasm is filled with haemoglobin. Haemoglobin is a red coloured iron-containing complex protein. Iron in haemoglobin is $Fe^{2+}$. Haemoglobin in blood conveys oxygen from the lungs to the remainder of the body. In the cells, it releases oxygen and thereby aerobic respiration takes place( required for energy production). Haemoglobin has a quaternary structure, containing four globular protein subunits. Each subunit has a protein chain tightly associated with a non-protein prosthetic heme group. Heme consists of iron ions held in a heterocyclic ring, called porphyrin. This porphyrin has four pyrrole molecules, cyclically linked together with iron ions bound in the centre.
So, the correct answer is option B.

Note: Myoglobin is an iron and oxygen restricting protein found in the skeletal muscle tissue of vertebrates and practically all warm-blooded animals. Myoglobin has only one globulin group, whereas haemoglobin has four. The heme group is identical in both haemoglobin and myoglobin. Myoglobin has a higher affinity for oxygen than haemoglobin. Haemoglobin transports oxygen, myoglobin function is to store oxygen.