Question

Question 37 Which of the following increases oxygen unloading? decreased BPG e decreased pCO2 in the plasma All of these answers are correct. increased blood pH increased body temperature Question 38 What is a classic scenario, as described in class, where oxygen unloading would be increased? while eating food during exercise during tidal volume breathing while drinking water

Answer 1

You have asked multiple questions here. As per Chegg Q&A Guidelines, I am answering only the first question which is Question 37.

The question is concerned with oxygen dynamics as mediated by hemoglobin. Hemoglobin is a protein molecule comprised of four domains. The dynamics associated with this molecule can load/unload oxygen molecules depending on the various factors. Since oxygen has o be transported from the lungs where the gas exchange occurs to the tissue where the oxygen is used for metabolism, hemoglobin exhibits a high affinity for oxygen near the lungs where it is loaded and low to almost zero affinity near the tissues where it has very little affinity.

There are various factors as I mentioned earlier which determine the affinity.

1. The partial pressure of oxygen: The partial pressure of X is the pressure exerted by the molecules of X in an ensemble of gas molecules. The partial pressure of oxygen is quite high near the lungs thus allowing oxygen molecules to be loaded onto the hemoglobin. On the other hand, the partial pressure of oxygen is lower near the tissues which don't favor the loading of oxygen onto the hemoglobin. In fact, this favors the unloading of the oxygen molecules. The partial pressure of oxygen near the lungs is 100 mm Hg while that near the periphery is 40 mm Hg.

2. In addition to binding O2 molecules, hemoglobin exhibits affinity for H+ too. The binding of H+ leads to conformational changes in the protein complex which leads to the release of O2 from the binding pocket. Hence as the pH decreases, the H+ concentration in the serum increases. This leads to unfavorable conditions for the haemoglobin molecule to hold on to O2. As a result, O2 is released. Naturally as one would expect, pH is lower near the tissue samples where oxygen has a high demand. This is called the Bohr effect.

3. Temperature also exhibits role in oxygen binding. Near the tissue samples, local temperature is higher. This results in conformational changes that disfavor the oxygen binding and as a result, oxygen is unloaded for the tissues to consume it.

4. 2,3-Biphosphoglycerate (BPG) is an intermediate that is formed during glycolysis. When the oxygen available is less, the concentration of 2,3-BPG increases. This accumulation leads to an increased affinity of hemoglobin to this molecule. In turn, the affinity for O2 decreases and O2 is released out.

5. CO2 exhibits an affinity for hemoglobin too. Near the lungs, the partial pressure of CO2 is low, and as a result, the affinity of hemoglobin for O2 is high. Additionally, the partial pressure of CO2 is high near the tissues because of a high metabolism rate. Hence the affinity of hemoglobin for O2 decreases. As a result, O2 is unloaded.

Thus of the given options, all of them are crucial at ensuring oxygen unloading when and where it is required.