Respiratory System: Hemoglobin’s Affinity for Oxygen Questions
1. The questions that follow pertain to the oxygen-hemoglobin dissociation curves below. For each
question, the middle line represents the normal oxygen-hemoglobin dissociation curve.
(a) Wow, you make it to the top of Mt Everest (30,000 ft)! On the basis of temperature, how would
the affinity of Hb for O2 change? In which direction would the normal curve shift (Left or
Right)?
(b) Still at the top of Mt Everest. . . On the basis of arterial CO2, how would the affinity of Hb for
O2 change? In which direction would the normal curve shift (Left or Right)?
(c) Back at sea level. . . You are seeing a patient (not at the top of Mt Everest) with emphysema
who has chronically elevated P CO2 How does your patient’s pH compare to normal? As a result
of this change in pH, how would the affinity of Hb for O2 change? In which direction would the
normal curve shift (Left or Right)?
(d) Cardiac and skeletal muscle contain a protein called myoglobin, which serves the same function as hemoglobin. In fact, the presence of myoglobin in the blood is sometimes used to confirm if a person is having a heart attack. Its main role is to serve as an O2 store for muscle in cases of severe oxygen deprivation. Which curve (Left/Right/Middle) would represent the expected affinity for oxygen of myoglobin compared to hemoglobin? Please defend your answer.
2. For the next 4 situations (a-d), please choose how the affinity of hemoglobin for oxygen would change
in each situation:
A. increase
B. decrease
(a) increased temperature
(b) increased pH
(c) increased P CO2
(d) increased 2, 3 ? DP G
3. Please draw a flow chart that shows the components of the reflex in which an increase in blood
P aCO2 leads to increased ventilation. Note which specific structure matches with each of the seven
general steps of a reflex arc.
4. Please write the chemical equation catalyzed by the enzyme carbonic anhydrase. Suppose the
concentration of H+ is increased by an outside force in a solution that had been at equilibrium. After
this occurs, how will the equation shift? What must happen to the CO2 concentration to reestablish
equilibrium after this disturbance? What must happen to the concentration of bicarbonate?
Expert Solution Preview
Introduction:
The questions provided are aimed at testing the understanding of the respiratory system and the affinity of hemoglobin for oxygen. These questions cover various factors that can affect hemoglobin’s affinity for oxygen and its implications in different scenarios. In addition, there are questions regarding the reflex arc involved in increased ventilation due to increased blood P aCO2 and the chemical equation catalyzed by carbonic anhydrase. Let’s go through each question separately to provide the answers.
Answer for question 1:
(a) At high altitudes like the top of Mt Everest, the temperature decreases. Based on the temperature, the affinity of Hb for O2 would increase. The normal oxygen-hemoglobin dissociation curve would shift to the left.
(b) Similarly, at high altitudes, the arterial CO2 levels decrease. A decrease in arterial CO2 would increase the affinity of Hb for O2. Therefore, the normal curve would shift to the left.
(c) In a patient with emphysema who has chronically elevated P CO2, the pH would be lower than normal (acidic). This change in pH would decrease the affinity of Hb for O2. As a result, the normal curve would shift to the right.
(d) Myoglobin has a higher affinity for oxygen compared to hemoglobin. Therefore, the curve representing myoglobin’s affinity for oxygen would shift to the left compared to the normal hemoglobin curve.
Answer for question 2:
(a) Increased temperature would decrease the affinity of hemoglobin for oxygen.
(b) Increased pH (alkaline conditions) would increase the affinity of hemoglobin for oxygen.
(c) Increased P CO2 would decrease the affinity of hemoglobin for oxygen.
(d) Increased 2,3-DPG concentration would decrease the affinity of hemoglobin for oxygen.
Answer for question 3:
A flow chart showing the components of the reflex where an increase in blood P aCO2 leads to increased ventilation would be as follows:
1. Stimulus: Increase in blood P aCO2
2. Receptor: Central and peripheral chemoreceptors
3. Afferent pathway: Sensory neurons
4. Integration center: Medulla oblongata (respiratory control centers)
5. Efferent pathway: Motor neurons
6. Effector: Diaphragm and intercostal muscles
7. Response: Increased ventilation
Answer for question 4:
The chemical equation catalyzed by the enzyme carbonic anhydrase is:
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
If the concentration of H+ is increased by an outside force in a solution that was at equilibrium, the equation would shift to the left, consuming H+ and forming more CO2 and H2O. To reestablish equilibrium after this disturbance, the concentration of CO2 would need to increase, and the concentration of bicarbonate (HCO3-) would decrease.
