Approximately what percentage of bound oxygen is released to the cells for metabolism during an erythrocyte's journey through the circulatory system?

25%

Explanation:

Oxygen taken in the lungs have to circulate to the tissues through the blood. The erythrocytes contains hemoglobin which has a heme part that binds to 4 molecules of Oxygen. As it begins to circulate around the body, the heme portion begins to release oxygen. And it releases approximately 25% as it circulates through the circulatory system