Hb Structure, Function and Gas Transport Flashcards
What determines how much oxygen can be carried in the blood (5)?

What can causethe amount of O2 dissolved in the blood to increase?
With high levels of inhaled oxygen the amount dissolved in the blood can become more significant.
What drives the movement of gases between the alveoli and the blood?
Partial pressures of CO2 and O2 in the respective environments. The gases will move from one environment to the other based on their respective pressure gradients.
When can perfusion limited gas exchange be transformed to diffusion limited?
During heavy exercise (with increase in cardiac output) or with a diffusion barrier the normal perfusion limitation can transform to diffusion limitation.
What are the ways that CO2 can be carried in the blood?
CO2 leaves tissues and enters blood. 5% of it remains dissolved and unchanged in the blood. 95% of it is taken up into the RBC and then 5% of it binds to Hb in the RBC. The remaining 90% of it is converted to H2CO3, which then rapidly decomposes to H+ + HCO3-. The proton can bind to Hb, making it have lower affinity for O2 so it will release more O2 to the tissues. The HCO3- is then pumped out of the RBC by a transporter that uses Cl-.

What does a pulse oximeter measure?
Whether or not hemoglobin has something bound to it. It DOES NOT distinguish between what is bound to hemoglobin. Thus, if a person has things other than oxygen bound to Hb, their pulse ox can appear normal and their arterial blood gas can reveal hypoxemia.
Concentration of a gas in solution depends on its […] in the solution
Partial pressure and solubility
What is the Bohr Effect?
Shift in oxyhemoglobin dissociation curve to left or right
What is the haldane effect?
The less O2 that is bound to Hb, the higher the affinity the Hb molecule has for CO2 and vice versa.

CO2 is able to diffuse across the alveolar/capillary membrane 20x faster than O2. However, these gases take the same amount of time to reach equilibrium with regards to gas exchange across this membrane. Why is this?
Although CO2 diffuses faster, the pressure gradient for O2 is larger so there is a larger driving force for O2 to cross the membrane. As such, they diffuse in about the same amount of time due to different driving factors.
If CO enters the blood, will it expert a partial pressure?
NO - Carbon monoxide has very high affinity for hemoglobin. If CO is introduced into the blood, very little exists in the plasma exerting a partial pressure and virtually all of the CO is bound to the hemoglobin.
How do you determine the partial pressure of a gas?
Each gas contributes to the total pressure in proportion to its concentration. I.e. if the total pressure of the gas is 760mmHg and the gas is 21% oxygen, then oxygen’s partial pressure is (760*0.21) = ~160mmHg
What does the CO2 dissociation curve look like?

What are the various forms that a gas can take in solution?
Dissolved gas
Bound to carrier (hemoglobin)
Chemically modified (CO2 being converted to HCO3-)
CO2 is […] more soluble in aqueous phase then O2
20 x
How many mL of O2 are “unloaded” to tissues during gas exchange in capillary beds of tissues?
5mL
In fully oxygenated blood there is about 20mL of O2 per 100mL of blood, in fully deoxygenated blood there is about 15mL of O2 per 100mL of blood

How do oxygen and carbon dioxide move from the alveoli into the blood?
Via diffusion - they are freely soluble in membranes
What things decrease the P50 of the oxyhemoglobin dissociation curve (i.e. increase affinity of hemoglobin for oxygen)?
Decreasing temp
Decreasing partial pressure CO2
Decreasing concentration of 2,3 BPG
Decreasing [H+]

What is the equation that describes alveolar respiratory membrane diffusion?

Why is an O2 sat of 90, 91, 92 concerning?
A patient with those levels of % oxygen has a partial pressure of about 60mmHg in their blood. If their blood saturation drops further, they are approaching an area of the dissociation curve where further deoxygenation can trigger a massive loss of oxygen binding due to the cooperative nature of oxygen binding to hemoglobin. This would put them at risk for becoming hypoxic and suffering tissue damage.

What is the PO2 and PCO2 in tissues before gas exchange occurs with oxygenated blood?
23mmHg
46mmHg
Why is the partial pressure of oxygen in the systemic arterial blood supply 100mmHg and the partial pressure of CO2 in the systemic arterial blood is 40mmHg?
Because these are the partial pressures of oxygen and carbon dioxide respectively in the alveoli. Gas exchange occurs until the partial pressures in the alveoli and the capillaries are equal, so that’s why the pressures are the same





