Final answer:
The steep region of the %saturation vs PO₂ curve is vital for oxygen release from hemoglobin, allowing rapid oxygen unloading to tissues needing it, especially under low oxygen conditions like those found at high altitudes.
Step-by-step explanation:
The steep region of the %saturation vs PO₂ curve is crucial for the efficient release of O₂ from hemoglobin as it permits rapid oxygen unloading to tissues that require it, such as those undergoing high metabolic activity. As the partial pressure of oxygen (PO₂) rises, hemoglobin increases its oxygen saturation; however, once it reaches around 60 mmHg, the curve begins to level off as hemoglobin approaches full saturation. This characteristic S-shaped, or sigmoid, curve facilitates partial unloading of oxygen where it is needed, allowing tissues to maintain sufficient oxygenation, particularly during conditions where oxygen levels are lower, such as at high altitudes or during periods of intense physical activity.
At higher altitudes, hemoglobin's oxygen saturation is reduced due to the lower partial pressure of atmospheric oxygen, which challenges the body's ability to maintain optimal oxygen saturation. Nevertheless, mechanisms like the production of BPG by erythrocytes enhance the release of oxygen from hemoglobin, ensuring sufficient tissue oxygenation even in these conditions. Under such circumstances, the ability of hemoglobin to readily release oxygen when the PO₂ drops becomes vitally important, highlighting the utility of the steep portion of the curve.