Question

How does pH affect oxygen dissociation curve?

Answer 1

Effect of pH on oxygen dissociation curve:

1. On the vertical axis, the oxygen–haemoglobin dissociation curve (ODC) displays the fraction of saturated (oxygen-laden) haemoglobin against the oxygen tension on the horizontal axis.
2. The oxyhaemoglobin dissociation curve is a graph that shows the relationship between oxygen saturation and blood oxygen partial pressure (PO₂) determined by "haemoglobin affinity for oxygen," or how easily haemoglobin collects and releases oxygen molecules into the fluid that surrounds it.
3. The standard curve moves to the right with a fall in pH (increase in H+ ion concentration) as it happens in tissues, while it shifts to the left with an increase, as it happens in the alveoli of lungs.
4. This happens because specific amino acid residues, such as Histidine-146, reside mainly in their protonated form at higher H+ ion concentrations, allowing them to form ion pairs that stabilize deoxyhaemoglobin in the T (Taut) state.
5. Lower pH causes haemoglobin to bind less O₂ for a given PO₂ because the T state has a lower affinity for oxygen than the R (Relaxed) state. Bohr effect is the name for this phenomenon.