- Carbon Dioxide causes pH to decrease
- Higher respiration=more CO2 in tissues= lower pH= greater change in shape of haemoglobin= so oxygen is unloaded more readily= so more O2 available for respiration
CO2 Concentration Affects Oxygen Unloading.
Hb gives up oxygen more readily at a higher pCO2.
When cells respire, they produce CO2, which raises pCO2 and increases rate of O2 unloading.
This means respiring tissues are supplied with plenty of O2, at a faster rate, meaning cells respire faster.
- Alveoli have high pO2 so oxygen loads onto haemoglobin to form oxyhaemoglobin.
- Respiring cells use up oxygen, which lowers the pO2
- Red blood cells deliver oxyhaemoglobin to respiring tissues, where it unloads oxygen
- Haemoglobin returns to the lungs to pickup more oxygen.
- Fetal Hb has a higher affinity for oxygen than adult Hb.
- Fetus gets blood form mother’s blood, across the placenta.
- By the time the mother’s blood reaches the placenta, the pO2 is lower, as oxygen has already been used up around the body.
- For fetus to get enough oxygen to survive, Hb has to have a higher affinity for oxygen.
At the same pO2, fetal Hb will be more saturated than Adult Hb.
- The Bohr Shift
- At the respiring tissues, there is a high pCO2 and a low pO2.
As a result haemoglobin's affinity for oxygen is reduced, meaning oxygen readily dissociates from Hb at the respiring tissues.
THE DISSOCIATION CURVE IS SHIFTED TO THE RIGHT
- Graph S-shaped because when Hb combines with first O2 molecule, shape alters in way which makes it easier for other molecules to join too.