The Gas Exchange System (CIE A Level Biology)

Fig.1 shows different structures in the human airways viewed in cross section under a light microscope.

Fig. 1

Identify the tissues or structures labelled A to C in Fig. 1.

Give one difference in the composition of C between the trachea and bronchi and the bronchioles.

Emphysema is a condition that can affect the lungs of individuals frequently exposed to cigarette smoke or high levels of air pollution. Fig. 2 shows two microscope images of the structures labelled B in Fig.1; one shows the normal structure of B while the other shows the structure of B when affected by emphysema. The images are shown at x40 magnification.

Fig. 2

The line marked X in Fig. 2 is 8.5 mm in length.

Use the information provided to calculate the actual diameter of the structure measured by line X. Give your answer in µm.

Individuals suffering from emphysema can experience a symptom known as cyanosis, where the fingers and lips take on a blueish discolouration.

With reference to Fig. 2 suggest why individuals with emphysema might experience cyanosis. Note that deoxygenated blood is darker in colour than oxygenated blood. 

Fig. 1 is an image of an electron micrograph showing a cross section through the lining of part of the human gas exchange system. The magnification of Fig. 1 is x5000.

Fig. 1

The line marked Z in Fig.1 measures 3.1 cm.

Calculate the actual length of the structure measured by line Z. Give your answer in µm.

For Fig.1:

[2]

(iii)

Name one location in the gas exchange system where the structures identified in part ii) would be found.

Explain the functions of structures X and Y in Fig.1.

Certain lung conditions can lead to remodelling of the lining of the airways and an increase in the numbers of structure Y from Fig.1. This is known as cell metaplasia and can lead to damaging symptoms.

Suggest three symptoms that may result from metaplasia of structure Y from Fig.1.

Fig. 1A is a photomicrograph of healthy lung tissue.

Fig. 1B is a photomicrograph of lung tissue from a person with emphysema, a chronic obstructive pulmonary disease (COPD). The images are both at magnification ×40.

Fig. 1

Name the structure labelled H in Fig. 1A.

Calculate the actual diameter of the alveolus at X–Y.

Write down the formula and use it to make your calculation.

When measured with a ruler on the page, the image of alveolus X-Y would appear as follows:

Give your answer to the nearest whole micrometre (μm).

Gas exchange in the lungs occurs in the alveoli.

Describe the process of gas exchange in healthy lungs and suggest how this compares with gas exchange in the diseased lung shown in Fig. 1B.

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.

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.

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.

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 Fig.1.

Fig. 1

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

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 called pulmonary surfactant. This can lead to a condition known as respiratory distress syndrome (RDS). Fig. 1 below shows the possible appearance of the lung tissue of an RDS patient and the appearance of normal lung tissue.

Fig. 1

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/ 

Identify and label on Fig. 1 healthy lung tissue.

[2]

[2]

RDS can be treated by the administration of an alternative form of pulmonary surfactant to the lungs. The graph shown in Fig. 2 gives the effect of different variations of pulmonary surfactant on the lung volume of rabbits at different pressures. The variations include pulmonary surfactant isolated from sheep lungs, as well as synthetic versions of pulmonary surfactant that contain its separate lipid and protein components. Note that cm H₂O is a unit of pressure.

Fig. 2

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

Pulmonary surfactant is essential for lung expansion.

[1]

(ii)

Phospholipids are the active component of pulmonary surfactant.

[1]

(iii)

Pulmonary surfactant from sheep is the most effective treatment for RDS in premature babies.

[2]

The form of pulmonary surfactant 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.

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

Fig. 1

Identify cell A and cell B and describe their function.

Cell A is adapted for its function. 

Describe and explain one feature of cell A that makes it well adapted as part of the gas exchange system. 

Scientists grew alveolar epithelium cells in culture for 10 days. The cells were exposed to hydrogen peroxide. Hydrogen peroxide is a toxin that is found in cigarette smoke. Each day the scientists calculated the mass of cells that died each hour. Their results are shown in Table 1 below. 

Table 1

For each day, calculate the rate of cell death per minute. Record the rates in standard form and give an appropriate unit.

[2]

Plot a suitable graph of your processed data on the grid in Fig. 2.

Fig. 2

[3]

Alpha-1-antitrypsin is a protein that reduces the activity of enzymes that can damage lung tissue. Hydrogen peroxide reduces the activity of alpha-1-antitrypsin. Scientists investigated the effect of different concentrations of hydrogen peroxide on the activity of alpha-1-antitrypsin.
Fig. 3 shows their results.

Fig. 3

Use Fig. 3 and the information from part (c) to explain why long term smokers suffer with shortness of breath.