Final answer:
The transfer of O₂ between myoglobin and hemoglobin occurs at the same O₂ pressure, with hemoglobin releasing O₂ in the tissues.
Step-by-step explanation:
The transfer of O₂ between myoglobin (Mb) and hemoglobin (Hb) occurs at the same O₂ pressure. In the lungs, hemoglobin binds with O₂ to form oxyhemoglobin (HbO₂). The high oxygen affinity of deoxyhemoglobin in the lungs allows it to be completely loaded with O₂. In the tissues, where the oxygen pressure is lower, the decreased oxygen affinity of hemoglobin allows it to release O₂, resulting in a net transfer of oxygen to myoglobin.