VIII: Hb and Gas Transport Flashcards
True or false: RBCs are as necessary for CO2 transport in the blood as they are for O2 transport.
true
Describe the Bohr effect.
As carbon dioxide is loaded into venous blood in the tissues, it helps facilitate the unloading of oxygen from the blood.
Describe the Haldane effect.
As oxygen is loaded into arterial blood in the lungs, it helps to facilitate the unloading of carbon dioxide from the blood.
How are the Bohr and Haldane effects related?
They explain the same physiological reactions in RBCs, but in reverse directions.
Why does molecular oxygen have such a low solubility in plasma but a high solubility in arterial blood?
This is due to the presence of hemoglobin in RBCs (Hemoglobin increases the effective solubility of oxygen in blood ~68x).
How does Hb increase the solubility of molecular oxygen?
As oxygen diffuses down its partial pressure gradient into pulmonary capillary blood, most of the oxygen molecules are bound to Hb as HbO2. However, bound O2 cannot contribute to the pO2 in the capillaries, so the gradient for more O2 to diffuse into the capillaries is maintained.
How is oxygen bound to hemoglobin?
covalently at the heme sites containing iron in the reduced ferrous state (Fe2+)
What is the normal value for oxygen capacity?
20.4 mL O2/dL
What does an oxyhemoglobin curve shift to the left mean, and what are some things that cause this type of shift?
It indicates increased binding affinity of oxygen to hemoglobin (therefore, less unloading to tissues). Things that cause this include a decrease in temperature, PCO2, or 2,3-DPG.
What does an oxyhemoglobin curve shift to the right mean, and what are some things that cause this type of shift?
It indicates a decreased binding affinity of oxygen to hemoglobin (therefore, easier unloading to tissues). Things that cause this include an increase in temperature, PCO2, or 2,3-DPG.
How does the concentration of 2,3-DPG change with altitude?
It is increased at higher altitudes in order to facilitate easier unloading of oxygen to the tissues.
How does the oxygen capacity change with a decrease in Hb concentration?
If hemoglobin concentration is halved, only half the number of binding sites remain, so the oxygen capacity is also halved.
How does P50 change with anemia?
It remains the same; the hemoglobin not abnormal– there’s just less of it.
How does P50 change with carbon monoxide poisoning?
It decreases, as CO binds to Hb with a much greater affinity.
Does the shape of the oxyHb curve change with carbon monoxide poisoning? How about with anemia?
With carbon monoxide poisoning, the shape becomes hyperbolic (similar to an oxymyoglobin curve). With anemia, the shape remains sigmoidal (there’s nothing wrong with the Hb– there’s just less of it).
