Savannah, GA (near sea level) Denver, CO (6,000 ft above sea level) ambient pO2

Question

Savannah, GA (near sea level) Denver, CO (6,000 ft above sea level) ambient pO2 tracheal pO2 alveolar po2 arterial pO2 159 mm Hg 149 105 100 95 mm Hg 86 50 45 Information on oxygen pressures are provided above for Savannah and Denver. You leave Savannah for a holiday skiing trip to Denver One day after arriving in Denver, the best prediction for [2,3 bisphosphoglycerate] and Pso for your body is (The symbols, , ,andrepresent increase, decrease, and remain the same, relative to Savannah.) 2,3-diphosphoglycerate A) B) c) D)

Explanation / Answer

At high altitude like Denver, the partial pressure of oxygen is less compared to the normal sea level place like Savannah. As it is shown, the partial pressure is P50 of oxygen is 95 mmHg compared to 159 mmHg. Due to this, P50 of artery is also less and hence oxygen reaching to the tissue becomes lower and hence tissue starve of oxygen (hypoxia condition). Hence in order to compensate this, body has several mechanisms. One is 2,3-biphosphoglycerate (DPG) which is present in human RBC at a concentration of 5mmol/lt. In case of hypoxia, the blood level of DPG increases. DPG has high affinity for deoxygenated hemoglobin and hence it binds to hemoglobin in its deoxygenated state. As DPG is bound, the affinity of hemoglobin for oxygen is reduces and hence more of oxygen is present in dissolved form in the blood which ultimately increases partial pressure of arterial oxygen. This is how body counteracts hypoxic condition at higher altitude.

Hence correct option is A.

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