Kim goes to Tanzania with the Peace Corps and while there decides to take a brea
ID: 178912 • Letter: K
Question
Kim goes to Tanzania with the Peace Corps and while there decides to take a break and climb Mt Kilimanjaro (the highest mountain in Africa). Although Kim is extremely fit and the climb requires him to do nothing more than walk at a leisurely pace up a gently sloping path, he finds that as the altitude gets higher he and his companions are all breathing much faster than normal. As Kim continues up the mountain he finds that he tires much faster than normal, that some of his fellow climbers can barely walk and that some are becoming irrational.
How does the prolonged rapid breathing associated with being at high altitude affect blood CO2 levels and blood pH?
How do the changes in blood CO2 and/or blood pH affect O2 – Hemoglobin binding affinity?
Why do the changes in O2 – Hemoglobin binding affinity affect the climbers in the way that they do?
Why would increasing the concentration of a ligand such as DPG (also known as BPG) in the blood counteract this effect to some extent?
Explanation / Answer
Ques-1: How does the prolonged rapid breathing associated with being at high altitude affect blood CO2 levels and blood pH?
Kim has experienced prolonged rapid breathing associated with being at high altitude affect and the follwoing are factors affected Kim for his blood CO2 levels & blood pH. At higher altitudes, oxygen levels reduced leading to hypoxia and hypocapnia result "reduction in PaO2".
According to the Bohr's principle, the oxygen binding affinity of the hemoglobin is inversely proportional to the concentration of carbon dioxide and acidity.
The right shift of the oxygen-hemoglobin curve indicates the less affinity of the hemoglobin towards oxygen, in this state, the hemoglobin releases more oxygen to the tissues.
The oxygen levels are generally lower at higher altitudes. This increases the rate of respiration to get enough oxygen to meet the metabolic demands. This decreases the blood CO2 levels and causes respiratory alkalosis.
Ques-2: How do the changes in blood CO2 and/or blood pH affect O2 – Hemoglobin binding affinity?
According to the Bohr's principle, the oxygen binding affinity of the hemoglobin is inversely proportional to the concentration of carbon dioxide and acidity.
The right shift of the oxygen-hemoglobin curve indicates the less affinity of the hemoglobin towards oxygen, in this state, the hemoglobin releases more oxygen to the tissues.
Ques-3:
The changes in O2 – Hemoglobin binding affinity is going to affect the climbers. Kim is going to higher altitudes result in lowering blood pressure, difficulty in breathing and thereby insufficient oxygen-Hb capacity further leads to lower supply of oxygen to the living cells such as cardiac muscle cells. At higher altitudes, oxygen levels reduced leading to hypoxia and hypocapnia result "reduction in PaO2".
Ques-4:
The atmospheric pressure of oxygen decreases at high altitudes. People climbing to higher altitudes are adapted to lower PO2 levels. One of the key change observed in this adaptation is increased 2, 3-BPG (2, 3- bisphosphoglycerate), which shift P50 to higher values.
2, 3-BPG decreases the oxygen binding affinity of hemoglobin by decreasing its affinity for oxygen due to alteration in conformational changes, oxygen is loosely bound to hemoglobin in the presence of BPG. So, increased levels of 2, 3-BPG makes more oxygen available to cells.
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