Role of haemoglobin in the transport of respiratory gases?????

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Hemoglobin is the oxygen binding protein present in the blood of many animals. It is present in the red blood cells. When the blood passes through the lungs, hemoglobin takes up oxygen from the lungs and bind to it. One molecule of hemoglobin binds to four molecules of oxygen. Oxygen-hemoglobin complex is then transported to various parts of the body.and oxygen is released into the tissues. 

Apart from oxygen transportation, hemoglobin has some role in transportation of carbon dioxide from body parts to lungs. About 10% of carbon dioxide transportation occurs through hemoglobin.