Oxygen transport

Question 1

What is the purpose of oxygen transport in the blood?

Answer 1

1. Production of ATP through aerobic respiration (38 ATP molecules produced per glucose molecule compared to 2 in anaerobic respiration)
2. Oxygen carried to tissues bound to haemoglobin (travels down “oxygen cascade”)

Question 2

How is oxygen transported in the blood?

Answer 2

Bound to Haemoglobin in RBCs

Question 3

What is the oxygen-dissociation curve and how does it get its shape (in healthy adults)?

Answer 3

The curve is plotted on axis representing the amount of oxygen bound to haemoglobin (% saturation) and the partial pressure of oxygen (pO2).

The curve is a sigmoidal shape which depicts a delay until the threshold minimum pO2 is reached before a steep incline as oxygen binds rapidly to haemoglobin. The curve then plateaus when haemoglobin is fully saturated and no more oxygen can bind.

Question 4

How is haemoglobin’s affinity for oxygen affected?

Answer 4

Unbound haemoglobin is in a “tense” state which has a low affinity for haemoglobin - the initial binding of the first oxygen molecule requires a threshold minimum pO2.

Once the first oxygen has been bound, the quaternary structure becomes “relaxed” and more receptive to oxygen, hugely increasing affinity

Question 5

What is the Bohr effect?

Answer 5

The Bohr effect refers to the shifting of the oxygen-dissociation curve to the right in acidic conditions due to haemoglobin having a lower affinity to oxygen in these conditions.

Factors shifting curve to the right are:
Low pH
Increased CO2 
Increased temperature 
Increased 2,3 DPG concentration (released in anaerobic respiration)

Question 6

What is the Haldane effect?

Answer 6

The Haldane effect refers to the shifting of the oxygen-dissociation curve to the left caused by increased oxygenation of blood in the lungs displacing CO2 (thus increasing removal of CO2)

Question 7

What are the physiological effects of chronic hypoxia?

Answer 7

1. Increased EPO (erythropoietin) production (which leads to increased red blood cell production)
2. Increased tissue capillary density
3. Increased 2,3 DPG levels
4. Increased ventilation

Question 8

What factors cause a shift to the right (Bohr effect) in the dissociation curve?

Answer 8

Low pH
Increased CO2
Increased temperature
Increased 2,3 DPG concentration (released in anaerobic respiration)

Question 9

What is haem?

Answer 9

Porphyrin compound coordinated to a single iron atom (in its ferrous form, Fe2+)

Question 10

What is the structure of haemoglobin?

Answer 10

Tetramer made up of 2 alpha and 2 beta globin chains in a variable quaternary structure (which is influenced by various inputs and its modification varies its affinity to oxygen)
Each coiled polypeptide chain has one haem and one globin component