Syllabus Edition

First teaching 2020

Last exams 2024

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Transport of Oxygen & Carbon Dioxide (CIE A Level Biology)

Exam Questions

2 hours39 questions
1a
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4 marks

Describe and explain two ways in which red blood cells are adapted to oxygen transport.

1b
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2 marks

Haemoglobin is a globular protein made of two alpha polypeptides and two beta polypeptides. Each alpha polypeptide consists of 141 amino acids and each beta polypeptide consists of 146 amino acids.

Calculate the difference in the number of amino acids and DNA bases required for a single alpha polypeptide vs a single beta polypeptide.

1c
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2 marks

A scientist is looking at a red blood cell under an electron microscope and takes an electron micrograph. The actual diameter of the red blood cell is 7µm but in the micrograph image it measures 5cm. This is shown in Fig. 1.

alveolus

Fig. 1

Calculate the magnification used by the scientist in Fig 1. Give your answer to the nearest 100.

1d
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1 mark

Mammals that live at different altitudes often have different haemoglobin.

Suggest how a mammal's haemoglobin might be adapted to live at higher altitudes.

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2a
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2 marks

Describe what is meant by the chloride shift.

2b
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3 marks

Hydrogen carbonate ions are formed in a two step process

(i)

Give the two equations that represent this two step process.

[2]

(ii)

Identify the name of the enzyme involved in these reactions. 

[1]

2c
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1 mark

Describe the importance of the chloride shift for red blood cells. 

2d
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3 marks

The chloride shift can be compared to the Bohr shift. 

Use a tick () or cross (X) to assign the statements to either the chloride shift or the Bohr shift. You may choose more than one statement for each shift.

  Bohr Shift Chloride Shift
Transport of oxygen out of red blood cells    
Transport of hydrogen carbonate ions out of red blood cells    
Transport of chloride ions into red blood cells    

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3a
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3 marks

With reference to the different partial pressures of oxygen (ppO2) throughout the body explain how haemoglobin supplies oxygen to different areas of the human body.

3b
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2 marks

The oxyhaemoglobin dissociation curves for adult haemoglobin (HbA) and foetal haemoglobin (HbF) are shown in Fig. 1 below.

hb-graph

Fig. 1

Explain the steep gradient seen in the curve seen for HbA in Fig. 1

3c
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1 mark

State what can be concluded from Figure 1 about the difference between HbF and HbA.

3d
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2 marks

Haemoglobin is a quaternary protein that is broken down in the liver.

Predict what haemoglobin will be broken down into and suggest one function of this breakdown product in the body.

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1a3 marks

Fig. 1 shows the structure of haemoglobin.

8-2-fig-1-1Fig. 1

Explain how the structure of haemoglobin relates to its function.

1b3 marks

Fig. 2 shows the oxygen dissociation curve for haemoglobin.

8-2-fig-1-2
Fig. 2

Explain what Fig. 2 shows about the relationship between partial pressure of oxygen (pO2) and the affinity of haemoglobin for oxygen.

1c
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2 marks

Calculate the difference in percentage saturation of haemoglobin with oxygen between a pO2 of 2 kPa and a pO2 of 8 kPa in Fig. 2.

1d3 marks

Anaemia is a condition in which an individual's blood contains less haemoglobin than usual. Individuals with anaemia can produce chemicals in their blood which influence the haemoglobin dissociation curve, as shown in Fig. 3.

2

Fig. 3

Suggest the advantage to an anaemic individual of producing chemicals that have the effect shown in Fig.3.

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2a3 marks

Fig.1 shows the oxygen dissociation curve for haemoglobin.

8-2-fig-4-1
Fig. 1

Use Fig.1 to complete the table below

Location Partial pressure of oxygen / kPa Percentage saturation of haemoglobin / % Rate of oxyhaemoglobin dissociation ( slow / fast) 
Capillaries branching from pulmonary artery 0.6    
Capillaries in respiring tissue   45  
Capillaries leading to pulmonary vein   98  

2b4 marks

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

Explain why this is the case.

2c2 marks

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

8-2-fig-4-2
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 altitude.

2d2 marks

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.

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3a
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5 marks

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.

[2]
3b
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3 marks

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

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

fig6-1-qp-octnov-2018-9700-21

Fig. 1

i)

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

Use Fig.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 Fig.1, explain the advantage to llamas of having an oxygen dissociation curve positioned to the left of the curve for humans.

[2]

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1a2 marks

Red blood cells are a type of specialised cell with a limited life span of around 120 days; at this point their function has declined and they are destroyed by white blood cells. During their life span, red blood cells are exposed to high levels of physical stress, as well as undergoing the loss of structure of proteins both within the cell and within their cell surface membranes.

Use this information and your knowledge of red blood cells to suggest and explain one special feature of red blood cells that contributes to their short-lived nature.

1b3 marks

Fig 1 shows some of the events taking place in and around a red blood cell as it travels through actively respiring tissues.

8-2-fig-2-1Fig. 1

(i)
Write a word equation to show the process taking place at P.

[1]

(ii)
Explain what is happening at points Q and S

[2]

1c2 marks

The process marked R in Fig.1 is involved in generating the Bohr shift. The Bohr shift occurs when carbon dioxide levels are increased from low to high, as shown in Fig. 2.

8-2-fig-2-2
Fig. 2

Explain the connection between process R in Fig.1 and the Bohr shift shown in Fig. 2.

1d2 marks

Explain the importance of the Bohr shift to metabolically active tissues.

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2a5 marks

Fig. 1 shows the oxygen dissociaton 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).

m-q1

Fig. 1

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

2b1 mark

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

    • HbA
    • HbF

2c3 marks

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.

(i)
Suggest how an increase in the expression of HbF could help to treat sickle cell disease.

[1]

(ii)
Suggest why HbF may not be a perfect replacement for HbA.

[2]

2d2 marks

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 Fig.1.

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3a
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6 marks

Fig. 1 below shows an oxyhaemoglobin dissociation curve. 

oxyhaemoglobin-dissociation-curve-sq

Fig. 1

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

3b
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4 marks

Fig. 2 shows the oxygen dissociation curves for myoglobin, M, and haemoglobin, Hmyoglobin-dissociation-curve

Fig. 2

Using Fig. 2,

(i)

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

[1]

(ii)

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

[3]

3c
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4 marks

The structure of myoglobin is shown in Fig. 3.myoglobin-sq

Fig. 3

(i)

Compare the structure of myoglobin with the structure of haemoglobin. 

[2]

(ii)

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

[2]

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