Exchange Surfaces (OCR AS Biology)

Exam Questions

3 hours38 questions
1a1 mark

Complete the following sentence. 

The size of an organism is ___________ proportional to its surface area to volume ratio.

1b1 mark

In an experiment using agar blocks immersed in a diffusion solution, the blocks are made up containing sodium hydroxide and universal indicator solution. Suggest a suitable solution to immerse these blocks in to examine diffusion.

1c2 marks

Two organisms are described in the table below.

  Organism A Organism B
Surface Area / cm2 18 970 79.8
Volume / dm3 70 0.019
SA:VOL ratio    


Complete the table
 by calculating the missing surface area to volume ratios. Do not include units. 

1d2 marks

The table from part c) shows two organisms, A and B. One of these is a mouse, the other is a human. Work out which animal is represented by A. Give a reason for your answer.

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2a2 marks

Describe and explain one example of how the human breathing system is adapted to achieve sufficient gas exchange despite humans’ low surface area-to-volume ratio.

2b2 marks

A molecule of oxygen would diffuse into a single-celled prokaryotic cell and reach the centre of the cell quicker than it would reach the centre of a single, eukaryotic cell.

Explain why.

2c1 mark

Basal Metabolic Rate (BMR) is a measure of the amount of energy expended by that organism within a given period of time when the organism is at rest.

Suggest one variable that can be measured as a way of determining BMR.

2d1 mark

Describe the relationship between Basal Metabolic Rate and the mass of an organism.

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3a3 marks

Figure 3.1 shows the parts of the breathing system of a certain species of insect. 

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Figure 3.1

Label the structures shown in Figure 3.1 with the letters A, B, C, D, E and F as follows:

 

Structure Label
Muscle tissue A
Spiracle B
Trachea C
Tracholes D
Air sac E
Exoskeleton F

3b1 mark

Referring to the diagram shown in Figure 3.2, identify the structure that provides the pressure changes required for increased breathing in an insect.

3c1 mark

All insects possess a rigid exoskeleton with a waxy coating that is impermeable to gases.

Suggest why insects do not use this outer surface for gas exchange with the air.

3d2 marks

In plants, guard cells change to cause stomata to open and close at different times of day.

Describe the nature of the change that guard cells undergo when stomata close at night.

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4a3 marks

Figure 4.1 shows the structure of the human gas exchange system.

9-1-fig-1-1
Figure 4.1

Identify structures V, W, and X in Figure 4.1.

4b3 marks

For Figure 4.1:

(i)

Identify one tissue type that is present in structures V, W, and X but not in structure Y.

[1]

(ii)

Explain the function of the tissue identified in part (i).

[2]

4c2 marks

Figure 4.2 is an image of a micrograph showing a cross section through structure Y.

9-1-fig-1-2Figure 4.2

Explain one structural adaptation visible in Figure 4.2.

4d2 marks

Identify and explain one other feature of structure Y that assists its function.

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5a
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2 marks

The table below shows some structures of the breathing system.

Structure Sequence (1st, 2nd, 3rd, 4th or 5th)
Trachea  
Alveolus  
Bronchus  
Facial airways  
Bronchioles  

Complete the table by indicating the sequence of structures that are passed through by a molecule of carbon dioxide during exhalation (from 1st to 5th).

5b1 mark

State the name of the organ that drives the processes of inhalation and exhalation in the breathing system.

5c3 marks

The exchange of oxygen occurs between the alveoli and the capillaries in the lungs.

(i)

Give the name of the process by which oxygen is transported from alveolar air into red blood cells.

[1]

(ii)

State one feature of the alveoli that increases the efficiency of gas exchange.

[1]

(iii)

Identify the gas, dissolved in the blood, with which oxygen is exchanged.

[1]

5d
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1 mark

Identify the tissue of the gas exchange system shown in Figure 5.1.

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Figure 5.1

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6a
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3 marks

The table below compares the features of the human gas exchange system. 

Complete the table by putting a tick (✓) in each box if the feature is present and a cross if the feature is absent in each structure. 

The first row has been done for you. 

Structure Structural feature present
Cartilage Elastic fibres Goblet cells Ciliated Epithelium Smooth muscle
Trachea ✓ ✓ ✓ ✓ ✓
Bronchi          
Bronchioles          
Alveoli          

6b
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3 marks

Complete the following sentences about the gas exchange system. 

Choose the correct words from the list below.

volume    airways    villi    bacteria    bronchioles   eaten   

cilia    nose    saliva    digested    throat   swallowed

Ciliated epithelial cells have projections called ............... .

The role of these projections is to sweep ............... , dust and mucus out of the ............... .

The dust and mucus are swept towards the ............... where they can be ............... and destroyed by stomach acid. 

6c
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2 marks

Figure 6.1 shows different structures in the human airways viewed in cross section under a light microscope.

9-1-fig-2-1Figure 6.1

Identify the structures labelled B in Figure 6.1 and name the process that takes place here.

6d
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2 marks

Explain one function of structure A in Figure 6.2.

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1a
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3 marks

The table compares the features of airways in the lungs.

Complete the table by putting a tick (✓) in each box if the feature is present and a cross (X) if the feature is absent in each structure.

The first row has been completed for you.

Structure Structural feature present
Cartilage Elastic fibres Goblet cells
Trachea ✓ ✓ ✓
Bronchi      
Bronchioles      
Alveoli      

1b
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4 marks

Ventilation of the lungs creates air movements that can be measured and recorded.

(i)

Name the apparatus used to measure and record these air movements.

 [1]

(ii)

The trace below shows a recording of ventilation movements from an individual subject.

q21b-paper-1-nov-2020-ocr-a-level-biology

Identify the maximum tidal volume of the subject.

[1]

(iii)

After 60 seconds, the subject was told to breathe in as deeply as possible and then breathe out fully.

Use the trace to calculate the vital capacity of the subject.

[2]

1c
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6 marks

Compare and contrast the mechanism of expiration during the first 60 seconds of the trace with the mechanism of expiration when the subject was told to breathe out fully.

1d
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5 marks

Complete the following statements about exchange surfaces.

Use the correct terms selected from the list below.

circulatory system    concentration gradient    diffusion pathway

              flow of air    lung capacity    surface area

                   surface area to volume ratio    ventilation

Large organisms have a large .............................................................. but they have a small ...................................................... This means they need a specialised exchange surface and a .................................................... .

Two features of an efficient exchange surface are:

  1. A good blood supply to maintain the ...............................................
  2. A short ....................................................

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2a
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2 marks

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.

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Figure 2.1

(i)

Name these holes.

[1]

(ii)

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

Name this fluid.

[1]

2b
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3 marks

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

2c
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2 marks

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.

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3a
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3 marks

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

(i)

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]

3b
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4 marks

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 .................................... 

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4a
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3 marks

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

9-1-fig-2-1Figure 4.1

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

4b
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1 mark

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

4c
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2 marks

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.

9-1-fig-2-2Figure 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.

4d
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4 marks

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. 

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5a
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4 marks

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.

5b
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2 marks

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.

5c
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3 marks

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.

5d
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4 marks

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.

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Figure 5.1

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

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1a2 marks

Figure 1.1 below shows the relationship between body mass and gill surface area in a species of shark. 

SH90kD4V_6Figure 1.1

Explain how increasing gill surface can cause the change in body mass shown in Figure 1.1.  

1b2 marks

A theory called the gill oxygen limitation theory (GOLT) states that the surface area of fish gills increases more slowly than fish metabolic requirements as body size increases. 

State how the graph provides support for the GOLT and suggest how this might affect fish growth.

1c3 marks

Figure 1.2 shows how the concentration of dissolved oxygen in water changes with temperature. 

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Figure 1.2

Use Figure 1.2 to predict and explain how climate change is likely to affect fish growth in the future. Refer to the ideas of the GOLT described in part b) in your answer.

1d3 marks

Scientists who disagree with the GOLT have several arguments, one of which is that the largest fish in the world, the whale shark, is found in tropical waters. The whale shark is a slow-moving filter feeder that comes to the sea surface to feed while spending long periods diving to deeper waters. Male whale shark growth levels off as they reach sexual maturity, while females grow slowly throughout their lives. 

Use the information provided to suggest and explain how scientists who argue for the GOLT might respond to the argument that the whale shark provides evidence against their theory. 

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2a3 marks

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

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Figure 2.1

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

2b1 mark

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.

2c3 marks

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.

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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.

2d3 marks

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. 

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3a1 mark

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.

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Figure 3.1

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

3b3 marks

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.

3c3 marks

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. 

3d3 marks

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. 

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4a4 marks

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

 

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Figure 4.1

i
)
Identify chemical T.
[1]
 
ii)
Describe what happens to the chamber lid when a person breathes in and out.
[3]
4b1 mark

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

4c2 marks

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

xeLCYiMb_5Figure 4.2

i)
Label Figure 4.2 with an X to indicate a point at which the person was breathing in.

 [1]

ii)
Calculate the volume of air breathed in during the first 60 seconds. 
[1]
4d2 marks

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. 

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  Figure 4.3

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5a1 mark

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

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Figure 5.1

State and explain which diagram represents the lungs during inhalation. 

5b5 marks

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. 

5c2 marks

Explain why the walls of the alveoli contain elastic fibers.

5d5 marks

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

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6a
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3 marks

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

6b
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4 marks

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.

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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/ 

(i)

Identify and label on Figure 6.1 healthy lung tissue.

[2]

(ii)
Explain the effect of RDS on the lung tissue shown in Figure 6.1.

[2]

6c
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4 marks

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.yu4lonm-h-1c

Figure 6.2

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

(i)

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]

6d
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2 marks

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.

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