Respiratory - Transport and exchange

Question 1

What is Dalton’s law of gas pressure?

Answer 1

The total pressure of a gas is the sum of the pressures exerted by each individual constituent, P_total = ∑P_individual_gases

Question 2

What is the partial pressure?

Answer 2

The contribution of an individual gas to the total pressure

Question 3

What is Henry’s law?

Answer 3

C = ∂P, Concentration of a dissolved gas is the solubility (constant of proportionality) times the partial pressure

Question 4

How can oxygen get transported in the blood?

Answer 4

In the plasma or bound to oxygen-haemoglobin

Question 5

How does O2 transport between plasma and haemoglobin?

Answer 5

In plasma it can only transport up to 3mlL-1 while haemoglobin can transport 200mlL-1

Question 6

How many oxygens can bind per haemoglobin molecule? What is this property called? What does this form?

Answer 6

0, 1, 2, 3 or 3 per haemoglobin molecule

Stoichiometry, the relationship between relative amounts of a substance

This forms oxyhaemoglobin (Hb + nO

Question 7

What kind of binding does haemoglobin have? Explain this

Answer 7

Co-operative binding

Getting the first oxygen molecule attached is hard but for each new molecule attached, attaching a new one gets easier

Question 8

How is the saturation of oxygen in the blood correlated to the partial pressure of blood?

Answer 8

It is sigmoidal (i.e. S-shaped graph)

Question 9

What is the benefit of the sigmoidal shaped relationship between partial pressure and oxygen saturation?

Answer 9

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

Question 10

Label the diagram, what is it showing? Explain

Answer 10

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

Question 11

How is the pH of the blood and the concentration of CO2 related?

Answer 11

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

Question 12

How does the amount of CO2 change when doing exercise? How does this affect O2 saturation?

Answer 12

When doing exercise the amount of CO2 increases

This causes the O2 saturation to decrease resulting in more O2 being released

Question 13

Besides the partial pressure of CO2, what else affects the oxyhaemoglobin equilibrium? How does it affect this equilibrium? When do these occur?

Answer 13

• 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)

Question 14

What does a shift to the right on the oxyhaemoglobin equilibrium mean?

Answer 14

It means that for the a given partial pressure of oxygen, a shift to the right will cause more oxygen to be dropped

Question 15

What does the oxyhaemoglobin equilibrium allow in terms of oxygen offload?

Answer 15

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)

Question 16

What are some factors that reduce the HbO2 (oxyhaemoglobin) equilibrium?

Answer 16

CO poisoning and anaemia

Question 17

How does CO poisoning affect HbO2 equilibrium?

Answer 17

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.

Question 18

How does anaemia affect HbO2 equilibrium?

Answer 18

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

Question 19

How is CO2 transported?

Answer 19

• ~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)

Question 20

How does the bicarbonate ion for CO2 transport form (what is the equations for it)?

Answer 20

Question 21

What enzyme causes the bicarbonate to turn back into CO2?

Answer 21

Carbonic anhydrase

Question 22

How can CO2 be removed from the body?

Answer 22

• Exhalation as CO2
• Urination as HCO3-

Question 23

What are the CO2/O2 disassociation relations?

Answer 23

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)

Question 24

What dictates the direction of this reaction? Explain

Answer 24

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

Question 25

How does carboxyhaemoglobin form?

Answer 25

It forms when the partial pressure of carbon dioxide is high (i.e. in the tissues)

Question 26

How does the partial pressure of oxygen and CO2 change in the arteries and veins? Why?

Answer 26

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