Mass transport in animals (Hb and the circulatory system)

Haemoglobin is made up of three polypeptide chains each with their own haem group which contains an iron ion and this is where haemoglobin gets its red colour. Each molecule of haemoglobin can carry four oxygen molecules.

Haemoglobin is made up of four polypeptide chains each with their own haem group which contains an iron ion and this is where haemoglobin gets its red colour. Each molecule of haemoglobin can carry four oxygen molecules.

Near the body cells, oxygen leaves the oxyhaemoglobin reforming haemoglobin. (also known as dissociation)

In the lungs, the oxygen joins the haemoglobin forming oxyhaemoglobin. This is a reversible reaction. (also known as association)

Near the body cells, oxygen leaves the oxyhaemoglobin reforming haemoglobin. (also known as dissociation)

In the lungs, the oxygen joins the haemoglobin forming oxyhaemoglobin. This is a reversible reaction. (also known as association)

The affinity of Hb describes how easily it gives up oxygen. Different conditions can change the shape and therefore the affinity of haemoglobin for oxygen allowing it to load and unload oxygen when required. The concentrations of oxygen and carbon dioxide can cause this change.

The affinity of Hb describes how easily it takes up oxygen. Different conditions can change the shape and therefore the affinity of haemoglobin for oxygen allowing it to load and unload oxygen when required. The concentrations of oxygen and carbon dioxide can cause this change.

Partial pressure (kPa) is a measure of the concentration of a gas.

Partial pressure (Pa) is a measure of the concentration of a gas.

Partial pressure of oxygen affects the affinity of haemoglobin towards oxygen: the affinity for oxygen decreases as the pO2 increases making unloading occur in the lungs due to the high pO2 and unloading in the respiring tissues due to the low pO2.

Partial pressure of oxygen affects the affinity of haemoglobin towards oxygen: the affinity for oxygen increases as the pO2 increases making loading occur in the lungs due to the high pO2 and unloading in the respiring tissues due to the low pO2.

the affinity of Hb decreases.

the affinity of Hb increases.

When Hb combines with the first oxygen molecule, its shape alters increasing the affinity for oxygen molecules making it harder for other oxygen molecules to join. As the Hb becomes saturated it becomes easier for the oxygen molecules to join, resulting in a ‘S-shaped’ curve with a steep portion in the middle. The steep portion is the point after the binding of the first oxygen molecule where its really easy for the other oxygen molecules to join – a small increase in pO2 causes a big increase in the amount of oxygen carried by the Hb. The shallow portion of the curve on both ends is where its harder for oxygen to combine (in low pO2 and when the haemoglobin is close to being fully saturated).

When Hb combines with the first oxygen molecule, its shape alters increasing the affinity for oxygen molecules making it easier for other oxygen molecules to join. As the Hb becomes saturated it becomes harder for the oxygen molecules to join, resulting in a ‘S-shaped’ curve with a steep portion in the middle. The steep portion is the point after the binding of the first oxygen molecule where its really easy for the other oxygen molecules to join – a small increase in pO2 causes a big increase in the amount of oxygen carried by the Hb. The shallow portion of the curve on both ends is where its harder for oxygen to combine (in low pO2 and when the haemoglobin is close to being fully saturated).

During exercise heat is produced, this increase in temperature helps the Hb unload oxygen more readily. The curve in this situation is to the right of Hb at normal temperatures.

During exercise heat is produced, this increase in temperature helps the Hb load oxygen more readily. The curve in this situation is to the left of Hb at normal temperatures.

Organisms in low oxygen environments have Hb which have a higher affinity for oxygen therefore the dissociation curve for these are to the left of that of the Hb in humans.

Organisms in low oxygen environments have Hb which have a lower affinity for oxygen therefore the dissociation curve for these are to the right of that of the Hb in humans.

Hb has a lower affinity for oxygen so that it can easily unload oxygen for use and so have a dissociation curve to the right of that of the Hb for humans.

Hb has a higher affinity for oxygen so that it can easily unload oxygen for use and so have a dissociation curve to the left of that of the Hb for humans.

CO binds irreversibly to Hb to form carboxyhaemoglobin preventing Hb from loading oxygen and delivering it to the body cells. Hb has a higher affinity for CO than oxygen.

CO binds reversibly to Hb to form carboxyhaemoglobin preventing Hb from unloading oxygen and delivering it to the body cells. Hb has a lower affinity for CO than oxygen.

It has a lower affinity for oxygen so that it can obtain enough oxygen. This is necessary due to the pO2 of the foetal blood being lower to that of the mother’s blood. The oxygen needs to be unloaded by the mother’s Hb and loaded onto the foetal Hb. The dissociation curve for foetal Hb is to the left of the normal adult curve.

It has a higher affinity for oxygen so that it can obtain enough oxygen. This is necessary due to the pO2 of the foetal blood being lower to that of the mother’s blood. The oxygen needs to be unloaded by the mother’s Hb and loaded onto the foetal Hb. The dissociation curve for foetal Hb is to the left of the normal adult curve.

A red protein containing haem, which carries and stores oxygen in muscle cells.

A muscle cell

It has a higher affinity for oxygen than Hb. It will unload the oxygen when the pO2 is very low and the Hb can’t supply the muscle with enough oxygen for respiration. The dissociation curve for myoglobin is to the left of the normal adult Hb curve and the foetal haemoglobin curve.

It has a lower affinity for oxygen than Hb. It will unload the oxygen when the pO2 is very low and the Hb can’t supply the muscle with enough oxygen for respiration. The dissociation curve for myoglobin is to the right of the normal adult Hb curve and the foetal haemoglobin curve.