Human Gas Exchange (AQA A Level Biology)

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

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

Carbon monoxide is a toxic gas that is found in cigarette smoke. Carbon monoxide can be absorbed into the bloodstream where it irreversibly binds with haemoglobin.

Scientists decided to investigate the concentration of carbon monoxide inside living rooms. Some of the residents of the living rooms used in the experiment were smokers while others were non-smokers. 

The scientists measured the concentration of carbon monoxide with the doors open and closed. Figure 1 below shows the scientists’ results. A value of ± 3 standard deviations from the average includes over 95% of the data.

Figure 1

Suggest why the inhalation of carbon monoxide is harmful.

Children's rights campaigners are advocating for a law that would make it illegal to smoke in a living room with anyone under the age of 18.

Their spokesperson said:

‘It is highly dangerous to smoke in an enclosed room with a child. It allows for levels  of deadly toxins such as carbon monoxide to build up rapidly, even within a short period of time. Furthermore, children breathe at a faster rate than adults, so they are likely to inhale more of the harmful toxins.’

Use the information provided and the Figure 1 to evaluate the spokesperson’s statement.

Figure 1 below depicts a section of the human gas exchange system.

Figure 1

Name 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.

Figure 2 below shows the changes in the volume of air in a woman’s lungs while breathing.

Figure 2

Explain how Figure 2 shows that the woman was breathing out between times W and X.

At what point does the woman begin to exercise. Explain your answer.

Describe two ways in which the trachea is adapted to help protect the lungs from infection by bacteria.

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.

Figure 1 below shows the results.

Figure 1

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

Using Figure 1, calculate the percentage decrease in the FEV for group 2 compared  with group 1.

Suggest two considerations that should have been taken into account to ensure that the results of this study were reliable.

The individuals in group 2 had recently experienced an asthma attack.

Explain how an asthma attack would cause a decrease in mean FEV, as shown in Figure 1.

Explain how the volume of the thorax increases during inspiration.

Figure 1 below shows a micrograph of thinly sliced lung tissue.

Figure 1

Calculate the actual size, in micrometres, of the alveolus diameter that has been measured in Figure 1.

Explain why the alveoli in Figure 1 appear to be of varying sizes and shapes.

Smoking cigarettes is a major risk factor for developing lung cancer. The smoke produced by cigarettes contains harmful substances which can cause the build up of tar in lungs.

Describe and explain the effect of tar in a smoker’s lungs in relation to gas exchange.

Forced expiration volume (FEV) is a measurement often used to indicate lung function. When measuring the FEV of an individual, they most do the following:

1. Breathe in as deeply as they possibly can

2. Breathe out as hard as they possibly can (forced expiration)

Describe and explain the mechanism by which an individual carries out forced expiration.

Asbestos is a material that was once commonly used in construction. Inhaling asbestos fibres can be extremely harmful for your lungs. Over time and repeated  exposure a build up of these small asbestos fibres can cause disease in the lungs, such as asbestosis.

The asbestos fibres are small enough to enter the bronchioles and alveoli of the lungs where they destroy the phagocytes and surrounding tissue. The lung tissue then becomes scarred and fibrous, with a reduced elasticity. The alveolar walls can also thicken as a result. 

It has now been discovered that individuals suffering from asbestosis are at a greater risk of developing lung cancer. The time lag between prolonged exposure to asbestos and the diagnosis of lung cancer is approximately 20–30 years.

Scientists investigated the number of cases of asbestos-related lung cancer reported within a specific region of Britain between 1990 and 2020 as seen in Figure 1 below.

Figure 1

Asbestos was banned from use in construction in 1999. 

Describe and explain the number of new asbestos-related lung cancer cases after 1999.

Not including the reduced elasticity already mentioned, explain how the changes to lung tissue caused by asbestos exposure reduces the efficiency of gas exchange.

Name one factor, not including asbestos, which can increase the risk of developing lung cancer.

The greatest volume of air a person can breathe out in 1 second is known as the forced expiratory volume (FEV). The forced vital capacity (FVC) is the greatest  volume of air a person can breathe out in a single breath.

Figure 1 shows the results for the volume of air breathed out by three groups of adults, X, Y, and Z. Group X had healthy lungs and groups Y and Z had different lung conditions that affect breathing.

Figure 1

Calculate the percentage difference in FEV for those in group Y compared with those who had healthy lungs.

Asthma affects the bronchioles and reduces airflow in and out of the lungs while fibrosis reduces the volume of the lungs but does not affect the bronchioles. 

Which group, Y or Z, contained people with asthma? Use the information provided and evidence from Figure 1 to explain your answer.

One of the symptoms of fibrosis is that small physical exertion such as walking 100 yards become difficult. 

Use information from Figure 1 to explain why. 

The diaphragm is a muscular barrier between the chest and abdominal cavity. When the phrenic nerve is injured, one or both sides of the diaphragm can become paralyzed causing reduced lung function. 

Describe and explain how the paralysis of the diaphragm can lead to reduced lung function. 

Scientists investigated the effect of a drug called albuterol which can be used to treat asthma. They divided a large number of asthma patients into three groups, A, B and C. The groups were treated as follows:

• Group A inhaled a fixed volume of spray containing albuterol everyday

• Group B was a placebo group

• Group C did not receive any treatment 

Suggest how group B should have been treated. 

The scientists measured the forced expiratory volume (FEV) of each patient at regular intervals. The FEV is the volume of air forced out of the lungs in the first second when breathing out. The scientists recorded each patient’s FEV before treatment started and after 30 days of treatment. They then calculated the mean increase in FEV1 for each group. Their results are shown in Figure 1 with the standard deviation.

Figure 1

Suggest why each measurement taken by the investigators was repeated several times.

Evaluate the effectiveness of albuterol in the treatment of patients with asthma. 

Suggest two ways the scientists could improve the validity of their investigation.  

Vehicles often emit many types of harmful chemicals such as carbon monoxide and sulfur compounds which contribute to pollution. Scientists wanted to investigate the link between pollution from vehicle exhausts and the number of cases of asthma   between 1991 and 2011. Figure 1 shows their results with standard deviations shown. 

Figure 1

Describe and explain the data from Figure 1. 

Pollution is partly made up of particulate matter which consists of tiny particles known as PM2.5. These particles have a diameter of less than 2.5 micrometres. The WHO guidelines suggest keeping an average concentration of PM2.5 under 10 micrograms per cubic metre of air (µg/m³), to prevent increased deaths.

These particles are so small that they can lodge in the lungs. Suggest two other ways in which particulate matter may contribute to health concerns. 

In 2013 a London student died, the cause of death was stated as air pollution which exacerbated the student’s asthma. Asthma is a condition in which the bronchioles become restricted. 

Explain how asthma may lead to serious health conditions.

Doctors did not make a link between air pollution on heavily used roads and the severity of asthma for many years. Suggest why.

Figure 1 shows a spirometer that can be used to investigate breathing. 

Figure 1 

i) Identify chemical T.

ii) Describe what happens to the chamber lid when a person breathes in and out.

State one precaution that should be taken to ensure accuracy when breathing through a spirometer. 

Figure 2 shows a spirometer trace from a 25-year-old. 

Figure 2

i) Label Figure 2 with an X to indicate a point at which the person was breathing in. 

ii) Calculate the volume of air breathed in during the first 60 seconds. 

Fibrosis of the lungs is a condition that reduces the volume of air that can be taken into the lungs per single breath. Sketch on Figure 3 below what you would expect the spirometer trace to look like if the 25-year-old had fibrosis. 

Figure 3

Figure 1 shows a tissue sample taken from a human lung. Two cells are labelled A and B.  

Figure 1

Identify cell A and tissue B and state their function

Doctors can determine the lung function of adults by measuring the Forced Expiratory Volume (FEV) which represents the maximum volume of air expelled in 1 second. 

Figure 2 shows the different ranges for FEV for adults in the UK. 

Figure 2

Suggest why the data is compared to the percentage of FEV at 25 years of age.

A journalist claimed that giving up cigarette smoking improves your quality of life and prevents smoking-related death. Use information from Figure 2 to evaluate this claim. 

A doctor stated that the data in Figure 2 could not be used to accurately predict lung function for individual smokers. Suggest two reasons why. 

Figure 1 shows how the lungs look at two different points of ventilation, A and B.  

Figure 1

State and explain which diagram represents the lungs during inhalation. 

Explain how the lungs are adapted to allow the rapid exchange of oxygen. You must include a description of how oxygen is exchanged into the bloodstream. 

Explain why the walls of the alveoli contain elastic fibers.

Describe and explain the mechanism by which air is taken into the lungs.