Transport of Oxygen 2

The Bohr effect

Fetal haemoglobin

Myoglobin

Transport of Oxygen 2

Hb is even more efficient that suggested by the dissociation curve

The amount of O2 carried by Hb depends not only on the p O2 but also the partial pressure of carbon dioxide.

Transport of Oxygen 2

At the tissues there is high [carbon dioxide] this reduces Hb affinity for oxygen so it gives it up.

Conversely at lungs there is low [carbon dioxide] so the Hb has a greater affinity for oxygen – so picks up more.

The result is thus, that under the same blood pO2 conditions, high levels of CO2 (acidic

conditions) will unload more O2 from the Hb

Oxyhaemoglobin releases its oxygen where it is most needed: to the actively respiring tissues.

Transport of Oxygen 2

Transport of Oxygen 2

The further the dissociation curve moves to the right, the more readily Hb gives up its oxygen.

Transport of Oxygen 2

The further the dissociation curve moves to the left, the more readily Hb picks up oxygen.

Fetal haemoglobin

The developing fetus obtains oxygen from its mum

Fetal and maternal blood run close together but never mix

This allows materials to diffuse from the blood of mum into the fetus and vice versa..

Fetal haemoglobin

Fetal haemoglobin

The dissociation curve of fetal Hb is to the left of adult Hb

This means fetal Hb combines with oxygen more readily than adult Hb

Fetal Hb has a higher affinity for oxygen.

Fetal haemoglobin

At the placenta the fetal haemoglobin can ‘steal’ oxygen form the maternal haemoglobin.

Myoglobin

In muscle there is another oxygen binding molecule called myoglobin.

Oxymyoglobin is much more stable than oxyhaemoglobin

Myoglobin

Myoglobin will only give up its oxygen at very low oxygen partial pressures.

Myoglobin

The myoglobin dissociation curve is a long way to the left of Hb.

At each partial pressure of oxygen, myoglobin holds onto much more oxygen than Hb.

Myoglobin

This enables myoglobin to act as an oxygen store.

Usually respiring muscle will get its oxygen from oxyhaemoglobin

Only if the partial pressure of oxygen falls very low will oxymyoglobin release its oxygen