Overview Oxygen-hemoglobin dissociation curve sigmoidal shape is characteristic of positive cooperativity binding of 1 O2 molecule to 1 subunit of deoxyhemoglobin increases affinity for O2 in adjacent subunits P50 is PO2 at which hemoglobin is 50% saturated ↑ P50 → ↓ hemoglobin affinity for O2 login to view 1 more bullet ↓ P50 → ↑ hemoglobin affinity for O2 login to view 1 more bullet Loading and unloading of oxygen in lungs PaO2 ≈ 100 mm Hg hemoglobin % saturation ≈ 100% facilitates maximal O2 loading into arterial blood in lungs in peripheral tissues PvO2 ≈ 40 mm Hg hemoglobin % saturation ≈ 75% facilitates O2 unloading into peripheral tissues Shift to right mechanism ↑ P50 → ↓ hemoglobin affinity for O2 → ↑ O2 unloading causes ↑ PCO2, ↓ pH (Bohr Effect) login to view 8 more bullets ↑ temperature login to view 1 more bullet ↑ 2,3-bisphosphoglycerate (2,3-BPG) login to view 4 more bullets Shift to left mechanism ↓ P50→ ↑ hemoglobin affinity for O2 → ↓ O2 unloading causes ↓ PCO2, ↑ pH (Bohr Effect) login to view 4 more bullets ↓ temperature login to view 1 more bullet ↓ 2,3-bisphosphoglycerate (2,3-BPG) hemoglobin F login to view 4 more bullets