Transport of Oxygen & Carbon Dioxide (CIE AS Biology)

Figure 1 shows the oxygen dissociation curve for the haemoglobin of adults (HbA), as well as for a special type of haemoglobin produced by the cells of foetuses prior to birth; this second type of haemoglobin is known as foetal haemoglobin (HbF).

Fig. 1

Describe and explain the shape of the curve for HbA shown in Figure 1.

Use Figure 1 to determine the percentage saturation of the following with oxygen at a partial pressure of oxygen of 4 kPa:

• HbA
• HbF

Sickle cell disease is a genetic condition in which a mutation in the gene coding for part of the haemoglobin molecule causes red blood cells to take on a sickled, or crescent, shape. This influences the ability of the red blood cells to pass easily through the capillaries.

An experimental treatment for sickle cell disease involves gene therapy to increase the expression of the gene that codes for HbF, a gene that is normally switched off in adults.

[1]

[2]

Another form of oxygen-binding protein that exists in the tissues of humans is myoglobin. Myoglobin is present in the muscles where it functions as an oxygen store. It has a higher affinity for oxygen than both HbA and HbF.

Sketch a suggested dissociation curve for myoglobin on Figure 1.

Figure 1 below shows an oxyhaemoglobin dissociation curve. 

Fig. 1

Using Figure 1 and your own knowledge describe the structure of haemoglobin and explain how it transports oxygen around the body.

Figure 2 shows the oxygen dissociation curves for myoglobin, M, and haemoglobin, H. 

Fig. 2

Using Figure 2

State the percentage saturation of myoglobin and haemoglobin when the partial pressure of oxygen is 1 kPa.

[1]

Explain the significance of the difference in percentage saturation that you have identified in part (i).

[3]

The structure of myoglobin is shown in Figure 3.

Fig. 3

Compare the structure of myoglobin with the structure of haemoglobin. 

[2]

Using Figure 3, explain the shape of the oxygen dissociation curve for myoglobin in Figure 2. 

[2]

The dissociation and binding of oxygen to and from haemoglobin in red blood cells produces a sigmoid curve. 

Explain the property of haemoglobin that causes this shaped curve. 

Fig. 1 below shows oxygen dissociation curves of haemoglobin at two different carbon dioxide concentrations. 

Fig. 1

The partial pressure of oxygen in the lungs is 100 mmHg and the partial pressure in metabolically active tissue is 40 mmHg. 

Identify the percentage saturation of haemoglobin with oxygen in the lungs and in metabolically active tissue. 

Figure 2 shows how changes in the partial pressure of oxygen (PO2) influence oxygen (O2) binding to, and dissociation from, haemoglobin alongside the oxygen content of whole blood.  

The human body contains approximately 5 litres of blood. The concentration of haemoglobin is 15 g per 100 ml of blood, when fully saturated there is 1.34 cm³ oxygen per gram of haemoglobin.

100 mmHg partial pressure of oxygen in found in arterial blood and 40 mmHg partial pressure of oxygen is found in venous blood.

Fig. 2

 [2]

A scientist comments that "venous blood is not deoxygenated". 

Use the information and your answers in part (b) to explain this.

Figure 1 shows the oxygen dissociation curve for haemoglobin.

Fig. 1

Use Figure 1 to complete the table below

During exercise, oxygen is released from haemoglobin more readily than is shown in Figure 1.

Explain why this is the case.

Figgure 2 shows the oxygen dissociation curves for the haemoglobin of three different mammal species; X, Y, and Z. 

Fig. 2

Species Z lives at sea level while species X lives at high altitude where the atmospheric partial pressure of oxygen is lower.

Suggest how the haemoglobin of species X enables it to survive at high altitudes.

Species Y lives at the same altitude as species X but is more metabolically active.

Suggest how the haemoglobin of species Y enables it to be more metabolically active.

Haemoglobin is a globular protein which is able to transport oxygen and is soluble in water.

(i)

Explain how the structure of a haemoglobin molecule makes it able to transport oxygen efficiently.

[3]

(ii)

Explain how the structure of a haemoglobin molecule allows it to be soluble in water.

Llamas are mammals that are adapted to live at high altitudes.

Figure 1 shows oxygen dissociation curves for haemoglobin of llamas and humans.

Fig. 1

i)

The partial pressure of oxygen in the lungs of mammals at 3500 m is 6.4 kPa.

Use Figure 1 to state the percentage saturation of haemoglobin of llamas and humans at an oxygen partial pressure of 6.4 kPa.

[1]

ii)

With reference to Figure 1, explain the advantage to llamas of having an oxygen dissociation curve positioned to the left of the curve for humans.

[2]

Transportation of hydrogen carbonate ions out of red blood cells results in a positive charge within the cell.

Describe the mechanism of red blood cells to prevent this electrical imbalance. 

Fig. 1 shows a red blood cell at a respiring tissue. 

Identify labels A -C on the diagram.

Fig. 1

Table 1 shows the difference in ion concentrations in arterial and venous blood. 

Table 1

Calculate the percentage change in chloride ions and suggest a reason for this difference. 

Give your answer to 3 significant figures. 

Red blood cells transport ions through a carrier protein.

Give the method of transport that this is this an example of.

Table 1 shows the partial pressure of oxygen at different saturations of haemoglobin. 

Table 1

Plot the haemoglobin saturation data from Table 1 and use these points to sketch the full oxyhaemoglobin dissociation curves for an elephant and a mouse.

Explain why the dissociation curve for the mouse is different to the dissociation curve for the elephant. 

Haemoglobin in the respiring tissues has a lower affinity for oxygen. 

Explain why.