Question

The number of oxygen molecules (O2) that can conjugate with one molecules of hemoglobin are ___

Answer 1

Haemoglobin is a red coloured iron containing pigment present in the RBCs. $O_2$ can bind with haemoglobin in a reversible manner to form oxyhaemoglobin. Hemoglobin (Hb), which is contained in red blood cells, serves as the oxygen carrier in the blood.

Each haemoglobin molecule can carry a maximum of four molecules of $O_2$. Binding of oxygen with haemoglobin is primarily related to partial pressure of $O_2$.

The mammalian hemoglobin molecule can bind (carry) up to four oxygen molecules.

So, the correct answer is "option B"