How many O2 molecules can be bound by each hemoglobin tetramer?
How many O2 molecules can be bound by each hemoglobin tetramer?
Hemoglobin is a red pigment present in the blood. This helps in the delivery of oxygen from the lungs to the tissues in the body and also helps to transport the carbon dioxide and protons from the tissues to lung for excretion.
Hemoglobin is a tetrameric protein means it contains four monomeric units. This hemoglobin has two parts, the apoprotein part called globin and the non-protein part called the heme. Together these two form the tetrameric protein. The globin contains four polypeptide or monomeric units - 2 and 2 chains. The alpha chain contains nearly 141 amino acids and the beta chain contains 146 amino acids. These four subunits are held together with the help of ionic bond, hydrogen bond, and hydrophobic interactions. Each of these subunits will have a heme group. Heme gives the blood its red color and each heme contains an iron ion at the center of a heterocyclic porphyrin ring. This iron ion in its Fe2+ redox state is responsible for reversible binding of oxygen. Thus, each subunit will hold one oxygen molecule and the entire hemoglobin or tetramer will therefore hold 4 oxygen molecules.
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