Answer:
The correct answer would be oxygen and carbon dioxide.
The main function of Red Blood Cells (RBCs) or erythrocytes is to transport oxygen from the lungs to all cells of the body. In addition, it transports carbon dioxide from cells to the lungs from where it is exhaled out.
RBCs contain iron containing biomolecule termed as hemoglobin. It can bind to oxygen as well as carbon dioxide in a reversible manner. It depends upon the partial pressure of the gases in a cell.
For example, at the alveolar site, the partial pressure of oxygen is high which increases the efficiency of hemoglobin towards oxygen. Oxygen then binds with hemoglobin in a reversible manner to form oxyhemoglobin.
At the cellular site, the partial pressure of carbon dioxide is higher as compared to that of oxygen. Consequently, oxygen is released and hemoglobin binds with carbon dioxide to form carbamino-hemoglobin.
