Q. How many molecules of oxygen can associate with a molecule of haemoglobin in man?

NTA AbhyasNTA Abhyas 2020 Report Error

A

One

B

Two

C

Three

D

Four

Solution:

The erythrocytes contain a red-coloured respiratory pigment called haemoglobin. It is an oligomeric globin which consists of 4 polypeptide chains joined to each other through non-covalent bonds. It contains a prosthetic group called haeme group. It is the main oxygen-carrying substance in RBCs. Each haemoglobin molecule contains four iron-containing haeme groups. Each haeme can bind to one molecule of oxygen, so each haemoglobin molecule can transport up to four oxygen molecules as oxyhaemoglobin. Approx 97% of oxygen is carried by haemoglobin. Only 3% of oxygen is transported in plasma in a dissolved state. The oxygen molecules bind to the haeme group through coordination bonds in a reversible manner. The bidirectional reaction is as follows:
$Hb+4O_{2}\rightleftharpoons_{T i s s u e s}^{L u n g s}Hb\left(\right.O_{2}\left(\left.\right)_{4}\left(\right.Fe^{+ 2}\left.\right)\left(\right.Fe^{+ 3}\left.\right)$

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