Haemoglobin Flashcards
Haemoglobin
It is a protein. It has 4 polypeptides, each associated with a haem group. Each can carry an oxygen molecule, so haemoglobin carries 4 oxygen molecules. It has a quaternary structure because it has more than 2 polypeptide chains. Different animals have different types of haemoglobin. This is because they have a different order of amino acids (primary structure).
Haemoglobin loading and unloading process
Haemoglobin carries oxygen which has a high affinity for oxygen.
This forms oxyhaemoglobin in the red blood cells. Loading happens in the lungs at a high partial pressure of oxygen.
Oxygen dissociates into the respiring tissue at a low partial pressure of oxygen.
Unloading is linked to a higher concentration of carbon dioxide.
The reason for the S-shaped (sigmoid) dissociation curve
The first oxygen binds to the haemoglobin causing a change in haemoglobins shape.
This change in shape allows more oxygen to bind easily therefore it as a greater saturation of oxygen.
If the oxygen dissociation curve is shifted to the right
Usually occurs with smaller animals with a large surface area to volume ratio. This is because they lose heat rapidly as respiration is faster.
Haemoglobin has a lower affinity for oxygen.
Oxygen dissociates to respiring tissues more readily at a higher partial pressure of oxygen.
This means the animal gets more oxygen to the cells for more respiration to generate heat.
If the dissociation curve is shifted to the left
Occurs with animals in environments with less oxygen.
Haemoglobin has a higher affinity for oxygen.
Haemoglobin is saturated with oxygen and dissociates at a low partial pressure of oxygen.
Link to the animal.
How the curve shifts to the right
If there is more respiration, there is more CO2. This lowers the pH (more acidic). Therefore this reduces the affinity for oxygen by the shape of the haemoglobin. The curve shifts to the right.
How people load more oxygen
They have more red blood cells. Therefore they have more haemoglobin. They can then load more oxygen. Usually in places with less oxygen.
