Follow the red blood cell as it travels from the lungs to typical body cells (e.g. muscle).

• The oxygen rich, high pH environment of the lungs, causes Hemoglobin to release 4 CO2 molecules and pick up 4 O2 molecules.
• The CO2 produced by the muscle cell during metabolism lowers the blood pH, the blood becomes more acidic.
• The high CO2 content and low pH causes Hemoglobin to release the 4 O2s, which diffuses into the cell.
• The 4 CO2s now binds with the Hemoglobin and rides it back to the lungs and out of the body.