Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO2 bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains.
Hemoglobin, the protein responsible for carrying oxygen in red blood cells, binds both oxygen and carbon dioxide.  However, carbon dioxide attaches to a different location than oxygen on the hemoglobin molecule. It joins with the N-terminal regions of the four globin chains that make up hemoglobin.