The haemoglobin binds with four molecules of oxygen (blue) in the lungs, and then releases them again when the blood passes through body tissues with low oxygen concentrations.

• 每个血红蛋白在肺泡中，与四个氧分子（蓝色）结合，然后在随血液经过身体中含氧量较低的组织时，将氧释放。