Final answer:
Oxyhemoglobin (HbO2) is the term for hemoglobin bound to oxygen, occurring when hemoglobin in the lungs binds with O2 to reach an oxygen saturation level of 95-96%. Binding capacity increases after initial oxygen molecules are bound, depicted by the sigmoidal oxygen dissociation curve.
Step-by-step explanation:
When hemoglobin is bound to oxygen, the complex is referred to as oxyhemoglobin (HbO2). Hemoglobin (Hb) alone refers to reduced hemoglobin, which means it is not currently bound to oxygen. The formula representing this binding is Hb + O2 → HbO2. In the lungs, hemoglobin becomes sarurated with oxygen—typically 95-96%—forming oxyhemoglobin as it binds with O2 at the heme iron centers. The ability for hemoglobin to bind to O2 increases with the number of oxygen molecules already bound, which means that it is easier to bind a second and third oxygen molecule than the first. However, the fourth molecule binds with more difficulty, leading to the sigmoidal shape of the oxygen dissociation curve. Factors such as partial pressure of oxygen and disease states can affect this oxygen-binding capability.