There is an accompanying passage to this, but the question is pretty much a discrete.
"If a native of the peruvian andes came down to sea level for the first time, what would be the net effect on his blood PCO2 levels?"
A. It would decrease B. It would increase C. It would increase and acidify the blood D. There would be no net effect
No one I've asked this question to has given me a reasonable expalantion for Kaplan's answer.
The correct answer to this question is D (no change).
Also, please mention what happened to respiratory rate upon descent, and mention why/how the Bohr and Haldane effects might affect this. Thanks.
I really don't think the Bohr or Haldane effect is necessary to answer this question. This is how I reasoned it: If I'm not mistaken, people who live in upper elevations where PO2 is considerably lower are able to acquire sufficient oxygen supply due to increase production in RBC's. By increasing RBC's, these individuals have more hemoglobin readily available, which in turn allows for more oxygen to be captured at a lower PO2. Compare this to someone at lower elevations with a smaller amount of hemoglobin. At higher elevations, these individuals would have to increase respiration to achieve adequate oxygen supply.
At lower elevations, where PO2 is higher, the peruvian (due to more Hb) would attain higher blood 02 levels (compared to the normal population). However, O2 is essentially a nutrient and so there's no need to adjust the body's metabolic rate to dispose of it. Oxygen diffuses from hemoglobin to tissues (where myoglobin is readily available); because there is a fixed amount of myoglobin, I suppose at some point myoglobin will be saturated and thus, the remaining O2 will remain bound to hemoglobin. The rate of respiration for this individual should remain the same and therefore, CO2 blood levels should remain constant as well.
By contrast, this is entirely different when comparing an individual who consciously (or unconsciously) alters their rate of respiration. For example, breathing rapidly causes more CO2 to be expelled from the blood. This displaces the equilibrium achieved in our body. If you recall the equilibrium between CO2 dissolved in water (CO2 + H2O --> H2CO3 --> HCO3- + H+), a reduction in CO2 levels will shift the equilibrium causing both HCO3- and H+ to be consumed; higher pH blood levels (alkalosis). If the individual inhaled less, CO2 levels would build up (excess) and result in the accumulation of H+ (acidosis).
The Haldane and Bohr effect play an important role in regulating hemoglobin affinity for O2. In a nut shell, near tissues, where H+, CO2, and O2 is low, Hemoglobin has low affinity for O2 (tense state) and thus O2 bound to hemoglobin is readily released to metabolically active tissues where it's needed. In the lungs where O2 is freely available and CO2 is low, hemoglobin has high affinity for O2 (relaxed state; more O2 to Hb) and CO2 is able to readily diffuse down its concentration gradient (exhalation).