I think what is neat is that red blood cells are anaerobic. That RBC perform all the task of transporting oxygen using hemoglobin. Within the hemoglobin are 2 alphas and 2 betas which is where you will also find iron. the red blood cells pick up oxygen in the capillary beds of the lungs and are transported to throughout the body, usually toward areas of lower concentrated oxygen levels. Remember the red blood cells aren't using the oxygen their carrying for energy, Red blood cells are powered by ATP. Quick note; when oxygen binds to iron it is known as oxhemoglobin and when oxygen departs from iron it is known as deoxyhemoglobin.