3.1.2 Animal transport – Carriage of Oxygen Flashcards
(13 cards)
Describe the structure of haemoglobin.
- It is made from 4 polypeptide chains (2 alpha and 2 beta).
- A haem group is associated with each polypeptide chain.
- Each haem group contains an iron ion (Fe2+) which can combine with one O2 molecule.
At what part of the body does haemoglobin have a high affinity for oxygen?
The gas exchange surface (alveoli).
At what part of the body does haemoglobin have a low affinity for oxygen?
At respiring tissues.
State the conditions that cause haemoglobin to have a high affinity for oxygen.
High oxygen partial pressure and low carbon dioxide partial pressure.
State the conditions that cause haemoglobin to have a low affinity for oxygen.
Low oxygen partial pressure and high carbon dioxide partial pressure.
What shape is an oxygen dissociation curve?
It is a sigmoid curve.
Why is it difficult for oxygen to bind to haemoglobin at low concentrations of oxygen?
At low oxygen partial pressures, the polypeptide chains are closely united so it is difficult to absorb the first oxygen molecule.
What happens once the first oxygen molecule binds to haemoglobin?
The polypeptide chains loosen so it is easier to load subsequent oxygen molecules.
Which way does the oxygen curve move for haemoglobin that has a higher affinity for oxygen?
It moves to the left.
Where is fetal haemoglobin produced?
The liver.
Where does gas exchange take place for a foetus?
The placenta.
How is fetal haemoglobin different to maternal haemoglobin?
Fetal haemoglobin has a higher affinity for oxygen than maternal haemoglobin (its curve is further to the left).
Why is it important that fetal haemoglobin has a higher affinity for oxygen than maternal haemoglobin?
- Because the placenta has a low partial pressure of oxygen.
- So the maternal haemoglobin dissociates from oxygen under the conditions of the placenta.
- The fetal haemoglobin has a higher affinity for oxygen so it is still able to associate with the oxygen at the placenta.
