Movement of Oxygen Flashcards
Mass Transport
What do haemoglobin molecules have? (2 points)
- A quaternary structure of 2 alpha and 2 beta polypeptide chains
- An Fe2+ ion that has affinity to combine reversibly with oxygen
Describe cooperativity. Why does it not work for the 4th oxygen?
The combination of the first haem group with an oxygen molecule increases the affinity of the second haem group for oxygen, which in turn increases the affinity of the 3rd haem group. Doesnt work for the 4th haem group as the probability of a 4th oxygen binding is low
What is the process by which haemoglobin binds to oxygen called?
Loading or associating
What is the process by which haemoglobin releases oxygen called?
Unloading or dissociating
What must haemoglobin do to transport oxygen efficiently? (two points)
- Readily associate with oxygen at gas exchange surfaces
- Readily dissociate from oxygen at tissues
When does haemoglobin change its affinity?
Under different conditions e.g. presence of carbon dioxide
What effect does having haemoglobin with a high affinity for oxygen do?
Associates oxygen more easily but is harder to dissociate
What effect does having haemoglobin with a low affinity for oxygen do?
Associates oxygen less easily but is easier to associate
What does the oxygen dissociation curve show?
Indicates haemoglobin’s affinity for oxygen as the pO2 changes
What is partial pressure?
A measure of a gas’ concentration
What can partial pressure be expressed as and it what units?
pO2 in kPa
What shape does the oxygen dissociation curve have?
An ‘s’ shape
How does a low partial pressure of oxygen affect an oxygen dissociation curve and why?
Makes the curve shallow as oxygen doesnt associate as easily because the shape of the haemoglobin makes it difficult
What effect can different conditions have on the oxygen dissociation curve?
Moves the curve on the x axis
Why do different conditions move the curve on the x axis?
Different conditions within organisms and different organisms have different types of haemoglobin which has different affinities of oxygen
What is the affinity of oxygen when the curve is shifted to the left?
Higher. It will associate with oxygen easier and dissociate less easily. Left Favours Loading
What is the affinity of oxygen when the curve is shifted to the right?
Lower. It will associate with oxygen less easily but dissociate more easily. Right Favours Release
What factors can influence the disassociation curve?
Temperature, pH, and CO2 concentration
Where does an increase in temperature, acidity and CO2 concentration displace the dissociation curve? What is this effect called?
To the right. The Bohr effect
Why is the Bohr shift significant?
It facilitates delivery of oxygen to the respiring tissues
What does a high CO2 concentration do to the haemoglobin?
Makes it less efficient at taking up oxygen but more efficient at releasing it
Why does the pH increase at the gas exchange surface?
There is low concentration of CO2 as it is being constantly removed, and a high concentration of oxygen. This increases the pH so the affinity for oxygen increases so more oxygen is associated
