Mass Transport: Animals Flashcards
Haemoglobin
Protein molecule with 4 polypeptide chains containing 4 haem groups, that transports oxygen
Haem group
contains ferrous/ fe2+ ion, each of which can combine with a single O2 so therefore 4 O2 molecules can be carried by a single haemoglobin molecule
Loading
aka Associating- when haemoglobin binds with oxygen.
occurs in the lungs
Unloading
aka dissociating- when haemoglobin releases its oxygen .
takes place in the tissue.
High affinity
hb with high affinity takes up oxygen more easily but releases it less easily.
Low affinity
hb with low affinity for oxygen takes it up less easily but release it more easily.
How is hb efficient at transporting o2?
readily associates with oxygen at the surface where gas exchange takes place.
readily dissociates from oxygen at the tissue requiring it
Can hb change its affinity?
Yes, it is able to change shape in the presence of certain substances such as CO2.
Conditions at gas exchange surfaces
1) O2 concentration is high
2) CO2 concentration is low
3) affinity is high so oxygen is associated
Conditions at respiring tissue
1) O2 concentration is low
2) CO2 concentration is high
3) affinity is low so oxygen is dissociated
Why are there different types of hb affinity?
Different species have hb made up of different seq of amino acid, so different tertiary and quaternary structure, so different ability to bind to oxygen
Oxygen dissociation curve
show the affinity of haemoglobin for oxygen
in certain conditions
show the relationship between oxygen levels (as partial pressure) and haemoglobin saturation
Cooperative binding
1st O2 binds, chnages quarternary shape, easier for next O2 to bind, easier for next.
4th binding hard as only one empty subunit.
Behaviour of hb at gas exchange surface (lungs)
> low co2
affinity for O2 increased
high O2 in lungs
oxygen more readily loaded by hb
curve more to the left
opposite at respiring tissue/muscles
Effect of CO2 on hb
dissolved carbon dioxide is acidic and the low pH causes hb to change shape
