Mass Transport Flashcards
Describe the structure of haemoglobin
A globular protein with a quaternary structure:
-4 coiled polypeptide chains
-4 heam groups
What to heam groups contain, and why are they known as a ‘prosthetic group’?
-Contains an iron ion that combines with oxygen molecules
-Prosthetic as they are not actually made out of amino acids, although a globular protein.
What is the role of haemoglobin?
Binds to O2 and transports it
What is ‘affinity’?
Ability of haemoglobin to bind or attract to O2
What is saturation?
When haemoglobin is holding the maximum amount of O2 it can bind to.
What is loading/association?
The binding of oxygen to haemoglobin
What is unloading/dissociation?
When oxygen detaches, or unbinds, from heamoglobin
Haemoglobin + Oxygen =?
Oxyhaemoglobin
What is the shape of an ‘Oxyheamoglobin dissociation curve’ and why?
S/sigmoid curve
Due to cooperative binding of O2 to the haem groups, e.g 1st one is the hardest, knock on effect, 4th is the easiest
How many oxygen molecules can heamoglobin hold?
4
What does the ‘oxyheamoglobin dissociation curve’ show?
-O2 is loaded in regions with a high partial pressure of O2 (e.g alveoli)
-O2 is unloaded in regions of low partial pressure of O2 (e.g respiring tissues)
What is ‘cooperative binding’?
When haemoglobin changes shape when the 1st O2 binds, which then makes it easier for further O2 molecules to bind.
-Always hardest for the first O2 to bind
What is the ‘Bohr Effect’?
When a high conc of CO2 causes the oxyhaemoglobin curve to shift right.
The affinity for O2 decreases because the acidic CO2 changes the shape of haemoglobin slightly.
What happens to the curve when there is a low pressure of CO2 in the alveoli? (Bohr shift)
Curve shifts left, increased affinity, loads more O2.
What happen when there is a high partial pressure of CO2 at respiring tissues? (Bohr shift)
Curve shifts right, decreased affinity, unloads more O2.
