Respiratory - Transport and exchange Flashcards
What is Dalton’s law of gas pressure?
The total pressure of a gas is the sum of the pressures exerted by each individual constituent, P_total = ∑P_individual_gases
What is the partial pressure?
The contribution of an individual gas to the total pressure
What is Henry’s law?
C = ∂P, Concentration of a dissolved gas is the solubility (constant of proportionality) times the partial pressure
How can oxygen get transported in the blood?
In the plasma or bound to oxygen-haemoglobin
How does O2 transport between plasma and haemoglobin?
In plasma it can only transport up to 3mlL-1 while haemoglobin can transport 200mlL-1
How many oxygens can bind per haemoglobin molecule? What is this property called? What does this form?
0, 1, 2, 3 or 3 per haemoglobin molecule
Stoichiometry, the relationship between relative amounts of a substance
This forms oxyhaemoglobin (Hb + nO
What kind of binding does haemoglobin have? Explain this
Co-operative binding
Getting the first oxygen molecule attached is hard but for each new molecule attached, attaching a new one gets easier
How is the saturation of oxygen in the blood correlated to the partial pressure of blood?
It is sigmoidal (i.e. S-shaped graph)
What is the benefit of the sigmoidal shaped relationship between partial pressure and oxygen saturation?
For a large range of high partial pressures, there is also a high oxygen saturation. However once passed a critical point (~70mmHg) there is a steep drop off in saturation of haemoglobin which is a large reservoir of oxygen to be accessed during exercise
Label the diagram, what is it showing? Explain
It is showing the Oxyhaemoglobin equilibrium (HbO2) where the oxygen saturation of haemoglobin changes with partial pressure of oxygen based on varying partial pressures of carbon dioxide
How is the pH of the blood and the concentration of CO2 related?
More CO2 makes the blood more acidic (7.2 for high CO2 vs 7.6 for low CO2) and for a lower pH (i.e. high CO2) results in a lower blood saturation
How does the amount of CO2 change when doing exercise? How does this affect O2 saturation?
When doing exercise the amount of CO2 increases
This causes the O2 saturation to decrease resulting in more O2 being released
Besides the partial pressure of CO2, what else affects the oxyhaemoglobin equilibrium? How does it affect this equilibrium? When do these occur?
- Increasing the acidity/decreasing pH causes a shift to the right
- Increasing the temperature causes a shift to the right
- This all happens during exercise (i.e. an increased offload of oxygen during exercise)
What does a shift to the right on the oxyhaemoglobin equilibrium mean?
It means that for the a given partial pressure of oxygen, a shift to the right will cause more oxygen to be dropped
What does the oxyhaemoglobin equilibrium allow in terms of oxygen offload?
It means that without changing the partial pressures of oxygens in the tissues, more oxygen can be offloaded by increase the partial pressure of CO2, increasing acidity and/or increasing exercise (i.e. during exercise more O2 can be offloaded to the cells)
What are some factors that reduce the HbO2 (oxyhaemoglobin) equilibrium?
CO poisoning and anaemia
How does CO poisoning affect HbO2 equilibrium?
CO has a much higher affinity for haemoglobin which means that it saturates the haemoglobin instead of the oxygen. This means the oxyhaemoglobin equilibrium (i.e. the amount of oxygen bound to haemoglobin) is greatly reduced.
How does anaemia affect HbO2 equilibrium?
The amount of haemoglobin in the blood is greatly reduced so that even though the haemoglobin is all saturated, there is less haemoglobin to transport oxygen
How is CO2 transported?
- ~9% as CO2 in simple solution (i.e. just dissolved in the plasma)
- ~13% as HbCO2 (carboxyhaemoglobin –> where the haemoglobin binds CO2 similar to how it binds O2)
- ~78% as HCO3- (bicarbonate ion)
How does the bicarbonate ion for CO2 transport form (what is the equations for it)?
What enzyme causes the bicarbonate to turn back into CO2?
Carbonic anhydrase
How can CO2 be removed from the body?
- Exhalation as CO2
- Urination as HCO3-
What are the CO2/O2 disassociation relations?
The more oxygen that is bound to the haemoglobin (i.e. the more oxyhaemoglobin), the less CO2 that can be transported as carboxyhaemoglobin (CO2 bound to haemoglobin)
What dictates the direction of this reaction? Explain
The partial pressure of oxygen
When there is a higher partial pressure of oxygen is high (i.e. in the lungs), oxyhaemoglobin (HbO2) is formed, when there is a low partial pressure of HbO2 (i.e. in the tissue) then HbO2 disassociates
How does carboxyhaemoglobin form?
It forms when the partial pressure of carbon dioxide is high (i.e. in the tissues)
How does the partial pressure of oxygen and CO2 change in the arteries and veins? Why?
For O2 the partial pressure is much higher in the arteries than in the vein because veins return haemoglobin that have dropped their oxygen content
For the CO2 the partial pressure increases only slightly between the arteries and the vein because most of the CO2 is transported in the blood as carbonic ion and only some as carboxyhaemoglobin so doesn’t affect the partial pressure much
