Exchange Surfaces (OCR A Level Biology)

Figure 2.1 below shows some of the events taking place in the gas exchange system of an insect over time. 

Figure 2.1

Explain the changes to gas concentration and spiracles shown in Figure 2.1.

In some insects the interval between spiracle opening can be a long time. Suggest why this discontinuous method of breathing might be advantageous to these insects.

There are several mechanisms used by aquatic insects to allow them to continue breathing oxygen while underwater. Two of these methods are shown in Figure 2.2 below. Method A uses an air bubble, while method B uses a layer of air called a plastron which forms around a series of incompressible hairs. Note that both oxygen and nitrogen can diffuse across the air-water interface.

Figure 2.2

The bubble shown in method A in Figure 2.2 is sometimes known as a ‘compressible gill’ and only allows insects to dive for a short period of time.

Use Figure 2.2 to suggest why this is the case.

Method B in Figure 2.2 is a plastron, or an incompressible gill, and allows insects to dive indefinitely.

Suggest how the plastron enables this. 

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. 3.1 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 3.1

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 3.1 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 3.1 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. 

Figure 4.1 shows a spirometer that can be used to investigate breathing. 

Figure 4.1

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

Figure 4.2 shows a spirometer trace from a 25-year-old. 

Figure 4.2

 [1]

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 4.3 below what you would expect the spirometer trace to look like if the 25-year-old had fibrosis. 

  Figure 4.3

Figure 5.1 shows how the lungs look at two different points of ventilation, A and B.  

Figure 5.1

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. 

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). Figure 6.1 below shows the possible appearance of the lung tissue of an RDS patient and the appearance of normal lung tissue.

Figure 6.1

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 Figure 6.1 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 Figure 6.2 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.

Figure 6.2

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.

When walking, the abdomen of caterpillars expands and contracts slowly. Air is taken into the tiny holes along the side of the body.

One of these holes is labelled in Figure 2.1.

Figure 2.1

Name these holes.

[1]

(ii)

Fluid is found in the tubes responsible for gaseous exchange in insects.

Name this fluid.

[1]

Outline the reasons why insects and other animals need well-developed transport systems.

A student planned to carry out a dissection of insect and fish gaseous exchange systems.The student planned to complete diagrams of the different tissues. They were advised to observe the following guidelines:

• use a sharp pencil
• use ruled label lines
• include a scale bar.

Suggest two further guidelines for the student to follow to ensure they present their diagrams clearly and accurately.

Many organisms have evolved specialised gas exchange surfaces. One feature of these structures is their large surface area to volume ratio.

Describe how the structures of the insect tracheal system and fish gills provide a large surface area for gas exchange.

[2]

(ii)

The lugworm, Arenicola marina, is a species of segmented worm that lives in burrows in damp sand. They have hair-like external gills that increase the surface area available for gas exchange.

Many other species of segmented worm do not have external gills.

Suggest why lugworms have evolved external gills

[1]

Mammals use lungs for gas exchange. The following passage describes how gases are moved in and out of the lungs.

Complete the passage using the most appropriate words or phrases.

When air enters the trachea, mucus secreted by .................................... cells traps dust and microorganisms. Air diffuses through the bronchi and the bronchioles. Smooth muscle in the bronchioles relaxes during the ‘fight or flight’ response. This response is produced by the sympathetic nervous system, which contains neurones that secrete the neurotransmitter .................................... . During inspiration, both the .................................... and external intercostal muscles contract. The internal intercostal muscles only contract when expiration is .................................... 

Figure 4.1 shows different structures in the human airways viewed in cross section under a light microscope.

Figure 4.1

Identify the tissues or structures labelled A-C in Figure 4.1.

Give one difference in the composition of C between the trachea/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.

Figure 4.2 shows two microscope images of the structures labelled B in Figure 4.1; 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.

Figure 4.2

The line marked X in Figure 4.2 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 Figure 4.2 suggest why individuals with emphysema might experience cyanosis. Note that deoxygenated blood is darker in colour than oxygenated blood. 

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 Figure 5.1.

Figure 5.1

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