Oxygen Transport

Question 1

List the factors which affect oxygen-haemoglobin binding

Answer 1

PCO2
pH
Temperature
[2,3-DPG]

Question 2

what do the factors affecting oxygen-haemoglobin binding also affect? What is this effect called?

Answer 2

The number of oxygen molecules bound to haemoglobin by altering the structural conformation of the Hb molecule and changing O2-Hb affinity. This has the effect of shifting the oxygen-haemoglobin dissociation curve to the right or to the left - known as the “Bohr Effect”

Question 3

How is O2-Hb affinity decreased?

Answer 3

increased CO2
increased temperature
decreased pH
increased [2,3-DPG]
......causes the dissociation curve to shift to the left

Question 4

How is O2-Hb affinity increased?

Answer 4

decreased CO2
decreased temperature
increased pH
decreased [2,3-DPG]
......causes the dissociation curve to shift to the right

Question 5

How does the Bohr shift help Haemoglobin with its function?

Answer 5

Allows oxygen to be stored at respiratory surfaces but allows oxygen to be released in respiring tissues.
Also helps to prioritise oxygen release to the tissues with the greatest demand as the conditions that reflect the greatest need for oxygen are where pO2 and pH are lowest and pCO2 is highest. e.g. working tissues would reflect a greater need for O2 than resting tissue.

Question 6

List the impacts of anaemia on blood oxygen transport

Answer 6

O2 content (total arterial [O2]) is decreased
PaCO2 is normal
Hb SaO2 (%saturation) is normal
[Hb] decreased
[Hb-O2] decreased

Question 7

List impacts of carbon monoxide poisoning on blood oxygen transport

Answer 7

O2 content (total arterial[O2]) is decreased
PaO2 is normal
Hb SaO2 (%saturation) is decreased
[Hb] is normal
[Hb-O2] is decreased

Question 8

What is anaemia?

Answer 8

Anaemia is a decrease in the number of red blood cells per unit of blood volume. This is usually due to:

• decreased production of RBCs
• rapid and excessive loss of RBCs

Question 9

How does anaemia affect blood oxygen transport?

Answer 9

Decrease in RBC density =
Reduction in [Hb], total O2 binding sites and O2 carrying capacity
BUT affinity of Hb is unchanged.
% of Hb binding sites that are occupied by O2 will remain the same - there are just fewer in total.
Therefore, Hb-O2 saturation and oxygen partial pressure within the plasma will be normal whereas the total O2 content of the blood will decrease

Question 10

How does carbon monoxide poisoning affect blood oxygen transport?

Answer 10

It decreases total O2 carrying capacity due to a decrease in the number of Hb binding sites available
[Hb] remains constant
Total O2 content of blood will decrease as less O2 is transported as binding sites are occupied with CO
SaO2 will fall as they compare the [oxyhaemoglobin] to total haemoglobin