Question

describe the structure of a molecule of hemoglobin and explain the role played by iron in the transport of oxygen

Answer 1

Hemoglobin:

Hemoglobin is iron - containing protein in the red blood cells and each red blood cell contains around 200-300 million molecules of hemoglobin.

Hemoglobin is made up of four polypeptide chains(Alpha1, Alpha2, Beta1, Beta2) arranged tetrahedrally.  The alpha and beta subunit is covered by a large, folded, polypeptide called Globin.

Between each subunits of the globin folds there is a hydrophobic pocket that contains heme group and two histidine molecules which are associated with each heme group.  

The two identical alpha chains and two identical beta chains are held together by hydrophobic interaction, hydrogen bonding and ion pairs between oppositely charged amino acid side chains.

The heme group consists of porphyrin ring attached to an atom called ferrous ion. These iron-porphyrin complexes coordinate oxygen molecules reversibly, an ability directly related to the role of hemoglobin in oxygen transport in the blood.

Role Played By Iron in the Transport of oxygen :

Iron is an essential element for human beings as it is participating in wide variety of metabolic processes including oxygen transport, DNA synthesis and electron transport.

Iron is the central atom of the heme group, a metal complex that binds molecular oxygen in the lungs and carries it to all other cells in the body that need oxygen to perform their activities.

Without iron in the heme group, the oxygen would not bind and thus no oxygen would be delivered to the cells.

In addition to hemoglobin, myoglobin also contains iron which helps to diffuse oxygen throughout the muscle cells and the cytochromes which supply the body with its energy currency.

After the iron has been delivered from the oxygen as a part of hemoglobin ,it binds to the carbon dioxide which is then transported back to the lungs which is then exhaled.