Hemoglobin is a protein that facilitates the transport of oxygen in red blood cells.
Hemoglobin has an oxygen-binding capacity of 1.34 ml of per gram.
In mammals, hemoglobin makes up 96% of a red blood cell’s dry weight and around 35% of the total weight. It also carries off about 25% of the carbon dioxide in the respiratory system
The mammalian hemoglobin molecule can bind to up to 4 oxygen molecules.