BioFlix Activity: Gas Exchange -- Key Events in Gas Exchange Part A - Key events in gas exchange Drag each label to the appropriate location on the flowchart. Carbon dioxide leaves the body when exhale. ? Oxygen enters red blood cells, where it binds to the protein hemoglobin. Breathing moves air in and out of the lungs. Oxygen diffuses from the blood to the body's tissues, and carbon dioxide diffuses from the tissues to the blood. 1797 Oxygen diffuses from alveoli in the lungs into capillaries. ? Reset Help