Haemoglobin, oxygen dissociation curve and the transportation of co2 Flashcards
What is the structure of haemoglobin?
-Large globular conjugated(inorganic haem group) protein.
-4 subunits, 2a 2b, each has 1 haem group. So each haemoglobin can bind to 4 oxygen
How does haemoglobin display positive co-operativity?
When the binding of one oxygen to the haem group changes the haemoglobins structure to increase its affinity for oxygen.
REVERSIBLE PROCESS
How does the shape change affect the affinity of haemoglobin?
1st bind is difficult, shape changes and increases affinity so binding sites become more receptive to o2. 2nd and 3rd are easy.
4th is hard, shape change makes it slightly less accessible for oxygen binding
What is an oxygen dissociation curve?
Percent haemoglobin saturation plotted against oxygen partial pressure.
What does it mean when the oxygen dissociation curve shifts to the right?
Bohr shift, in presence of higher co2 it shifts to the right meaning it has a lower affinity for oxygen.
Means it can release o2 more readily, harder to bind to it(seen in tissues)
Where in the body is there a higher affinity for oxygen in the haemoglobin?
In the lungs, means it can bind to o2 more easily and is less likely to release it.
Explain foetal haemoglobin.
Higher affinity for o2 due to its 2a and 2g subunits.
Allows the foetus to take o2 from mothers haemoglobin in the placenta
Explain how co2 is transported
- Co2 from respiring cells diffuses into TF then into RBC
- Co2+H2o H2Co3(carbonic acid). Catalysed by carbonic anhydrase
- H2Co3 dissociates to form H+ and HCO3-(hydrogen carbonate) ions
- H+ ions bind with HB to form HHB(haemoglobinic acid)
- Hydrogen carbonate ions leave RBC to maintain steep conc grad for Co2 diffusion, CL- ions move into RBC to restore negative charge(chloride shift)
- In the lungs the process reverses to form co2 which can be exhaled.
