Oxyhemoglobin formation An oxygen molecule reversibly attaches to the heme portion of hemoglobin The heme unit contains iron(+2)which provides the attractive force O+ hb Hbo7 Oxyhemoglobin Formation • An oxygen molecule reversibly attaches to the heme portion of hemoglobin. • The heme unit contains iron ( +2 ) which provides the attractive force. O2 + Hb HbO2