1.1. The alveoli are structures in the lungs that maximise the efficiency of gas exchange in mammals.

Describe the process of gas exchange that takes place in the alveoli.

1.2. An adult has a total alveolar surface area of 5.2 x 10⁷ mm². One alveolus has a surface area of 0.104 mm².

Calculate how many alveoli this person has in each lung. Give your answer as an ordinary number, not in standard form.

1.3. Allergies occur when the immune system responds to a normally non-harmful antigen known as an allergen. Some allergic reactions affect the gas exchange system and can make breathing more difficult.

Suggest the events that could occur in the gas exchange system in response to an allergen that might make breathing more difficult.

1.4. Serious allergic reactions can sometimes lead to asthma attacks which can be very dangerous.

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 every day

• Group B was given an inhaler that contained no active drug

• Group C did not receive any treatment

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 FEV for each group. Their results are shown in Figure 5.1.

Figure 5.1

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