Question

The graph below shows the hemoglobin dissociation curves (also called equilibrium curves) for normal blood pH (the blue curve) and two other conditions.

Given what you know about the Bohr shift, what is the difference in O2 saturation of hemoglobin in the lungs versus hemoglobin in exercising tissues, as represented on this graph? Keep in mind that the pH of blood in the lungs is not the same as the pH of blood in exercising tissues.
Express your answer in percent, but do not include the percent sign in your answer.

Answer 1

The right answer is 57 (%)

The Bohr effect is the decrease of the oxygen attached to the hemoglobin when the pH decreases or when the CO2 level increases.

at the level of the lungs, one tends to find slightly alkaline pH due to the reduced CO2 pressure compared to the blood level, therefore the affinity of the oxygen with the hemoglobin is high and corresponds to the green curve. or the saturation of oxygen is 100% to 100mmHg of oxygen.

At the tissue level, there is more CO2 (waste) and less O2 (since it is consumed) and the pH is more acidic than that of blood pH (due to CO2 and the decrease of bicarbonate at this level) . This causes a deviation of the curve to the right as shown in the diagram with the red color curve. A saturation coefficient of 43% at 30 mmHg of the oxygen can be observed.

When subtracting between the two values: 100 - 43 = 57%