CBSE Class 10 Answered

The blood serves to transport both carbon dioxide and oxygen. Oxygen is carried to the cells whereas carbon dioxide is carried away from the cells.

In the lungs, oxygen diffuses from alveolar air into the blood because the venous blood has a lower partial pressure. The oxygen dissolves in the blood. Only a small amount is carried as a physical solution (0.31 ml per 100 ml). The remainder of the oxygen is carried in chemical combination with the hemoglobin in red blood cells.

Oxygen is bound to the iron of hemoglobin for the transport process and forms oxyhemoglobin.

Carbon dioxide produced in the tissue cells diffuses into the blood plasma. The largest fraction of carbon dioxide diffuses into the red blood cells. The carbon dioxide in the red blood cells is transported as dissolved carbon dioxide (7 per cent), combined with hemoglobin, carbaminohemoglobin (23 per cent) or as bicarbonate (70 per cent).