Gas Exchange (DP IB Biology: SL)

The diagram below shows a cross section of an alveolus and associated structures.

Describe the route taken by an oxygen molecule from an alveolus to the blood.

Explain how the fluid secreted by the epithelial cells of the alveolus helps to reduce surface tension and prevent adhesion of the alveolar surface.

State the mode of molecular transport by which oxygen from air in the alveoli enters the blood in capillaries.

Explain how the volume of the thorax increases during inspiration.

The diagram below shows a micrograph of thinly sliced lung tissue.

Calculate the actual size, in micrometres, of the alveolus diameter that has been measured in the diagram.

The diagram below shows the structure of the human gas exchange system

 Identify structures E and F

Explain how the downward movement of the diaphragm leads to air entering the lungs

Describe and explain two adaptations of alveoli that enable rapid gas exchange.

Describe the route taken by a carbon dioxide molecule from the blood to the outside air.

Two groups of people were asked to take part in a study. The individuals in group 1 were healthy and the individuals in group 2 had recently recovered from an asthma attack.

In the experiment each individual was asked to breathe in as deeply as they could. They then breathed out via forced expiration.

A study coordinator measured the volume of air that each individual breathed out during forced expiration.

The graph below shows the results.

The FEV (forced expiration volume) is the volume of air that an individual can breathe out within a single second.

Using the graph, calculate the percentage difference in the FEV for group 2 compared with group 1.

 The diagram below depicts a section of the human gas exchange system.

 Figure 1

State the name of Organ 1 and describe its role in breathing out.

In normal and healthy lungs, an oxygen concentration gradient is maintained between the alveoli and the lung capillaries. Describe and explain how this is maintained.

The graph below shows the changes in the volume of air in a woman’s lungs while breathing.

Explain how the graph shows that the woman was breathing out between times W and X.

Muscle action during ventilation is described as antagonistic.

Outline what this means with reference to one example during ventilation.

One mark is available for clarity of communication throughout this question.

Emphysema is an example of a Chronic Obstructive Pulmonary Disease (COPD).

Explain the consequences smoking has on lung tissue and the increase of symptoms of emphysema.

Lung cancer is another disease that affects the respiratory system. Many scientific studies have shown a link between smoking and lung cancer.

Describe other factors that may cause lung cancer.

Doctors investigated the effect of the smoking habits of men on their non-smoking partners.

The doctors recruited 640 non-smoking partners, all of which were women aged 30 or older. They divided these women into groups according to the smoking habits of their husbands. After 15 years, the doctors recorded how many of the partners had died and their cause of death.

They used these data to determine the relative risk of a partner dying from a particular disease according to her husband’s smoking habit.

 In this comparison, they gave the relative risk to the partner of a non-smoker as 1.00. A value greater than 1.00 shows an increased risk compared to the partner of a non-smoker.

The results are shown in the table below.

The scientists concluded from these data that if a husband smoked, it greatly increased the risk of his partner dying of certain diseases.

Evaluate this statement.

Describe the pathway taken by a molecule of oxygen from the outside air to the blood of a human.

Premature babies can suffer from a deficiency of a substance referred to here as substance X. This can lead to a condition known as respiratory distress syndrome (RDS). The image below shows the possible appearance of the lung tissue of an RDS patient (left) and the appearance of normal lung tissue (right).

Image courtesy of Atlas of Pulmonary Pathology, licensed under the Creative Commons Attribution-ShareAlike 2.0 Generic license, and adapted and redistributed under conditions found at https://creativecommons.org/licenses/by-sa/2.0/ 

Suggest the identity of substance X.

[1]

[2]

RDS can be treated by the administration of an alternative form of substance X to the lungs. The graph below shows the effect of different variations of substance X on the lung volume of rabbits at different pressures. The variations include substance X isolated from sheep lungs, as well as synthetic versions of substance X that contain its separate lipid and protein components. Note that cm H₂O is a unit of pressure.

Use the information provided to explain why each of the following statements is incorrect:

Substance X is essential for lung expansion.

[1]

(ii)

Phospholipids are the active component of substance X.

[1]

(iii)

Substance X from sheep is the most effective treatment for RDS in premature babies.

[2]

The form of substance X produced in mammalian lungs contains proteins known as SP-A and SP-D, which are known to be involved with the activation of phagocytes.

Suggest, with a reason, a symptom that would result from a deficiency of SP-A and SP-D proteins.

A study was carried out that looked at the movement of the diaphragm during normal breathing. The graph below shows the diaphragm movement in a healthy 55-year-old male.

Calculate the breathing rate of the individual shown in the graph.

[1]

For the stage marked Y on the graph, name a muscle other than the diaphragm involved at this stage and identify its state. 

[2]

The graph below shows the results of another participant in the study. This individual is a 57-year-old male with emphysema.

Contrast the graph shown here with the graph in part a).

[2]

Suggest an explanation for the differences between the graphs.

[2]

Events such as surgical trauma or nerve degeneration can lead to weakness or even paralysis of the diaphragm.

Suggest the effect that this would have on ventilation.

The graphs below show smoking prevalence and lung cancer deaths in men and women in the UK between 1950 - 2000.

Calculate the percentage decrease in smoking prevalence between 1950 - 1990 for:

Men

[1]

Compare and contrast the trends in smoking prevalence and lung cancer deaths between men and women in the graphs shown in part a).

A student looked at the graphs in part a) and concluded that cigarette smoking causes lung cancer.

Evaluate this conclusion from the graphs shown.

Data from other studies provide support for the student's conclusion in part c) and scientists now accept that smoking can cause lung cancer.

Explain the link between smoking and lung cancer.

Certain types of lung disease can be categorised as either obstructive or restrictive. The effect of obstructive and restrictive lung diseases on ventilation can be seen in the graph below, where:

• Tidal volume (TV) = the volume of air breathed in and out with each normal breath
• Inspiratory reserve volume (IRV) = the additional volume of air that can be drawn into the lungs during a large inward breath
• Expiratory reserve volume (ERV) = the additional volume of air that can be expelled from the lungs during forced expiration
• Residual volume (RV) = the volume of air that remains in the lungs after forced expiration

Compare and contrast the effects of obstructive and restrictive lung disease.

An example of an obstructive lung disease is emphysema.

Suggest how emphysema causes the features of an obstructive lung disease shown in the graph in part a).

Explain why sufferers of both obstructive and restrictive lung disease find exercise difficult.

Use the graph in part a) to suggest what might be happening to the lungs in a restrictive lung disease.

One mark is available for clarity of communication throughout this question.

Outline the need for a ventilation system in mammals.

Draw an annotated diagram to explain the process of inspiration.

Explain how the lungs are adapted to their function.