Getting More out of Hemoglobin Your body has increased the flow of oxygen-rich blood to your muscles, but your muscles still need to get the oxygen out of the blood. An exchange of oxygen and carbon dioxide is the key to this. A protein called hemoglobin , which is found in red blood cells, carries most of the oxygen in the blood. Hemoglobin in red blood cells entering the lungs has carbon dioxide bound to it. In the lungs, oxygen concentration is high and carbon dioxide concentration is low due to breathing.
Hemoglobin binds oxygen and releases carbon dioxide.
Hemoglobin gets transported through the heart and blood vessels to the muscle. In muscle, the carbon dioxide concentration is high and the oxygen concentration is low due to metabolism. Hemoglobin releases oxygen and binds carbon dioxide. Hemoglobin gets transported back to the lungs and the cycle repeats. The low pH reduces the attraction between oxygen and hemoglobin and causes the hemoglobin to release more oxygen than usual.