| Date | May 2019 | Marks available | 3 | Reference code | 19M.2.SL.TZ1.4 |
| Level | Standard level | Paper | Paper 2 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 4 | Adapted from | N/A |
Question
The diagram shows the structure of an alveolus and an adjacent capillary.
[Source: © International Baccalaureate Organization 2019]
Outline the functions of type I and type II pneumocytes.
Explain how gases are exchanged between the air in the alveolus and the blood in the capillaries.
Markscheme
type I:
a. carry out gas exchange
OR
diffusion of gases/CO2/O2 ✔
type II:
b. secrete fluid/surfactant ✔
a. O2 concentration in alveolar air greater than in capillary/blood «prior to gas exchange»
OR
hemoglobin in blood binds oxygen maintaining the concentration gradient ✔
b. O2 gas dissolves in water lining the alveolus ✔
c. O2 diffuses through wall of alveolus and capillary into blood ✔
d. CO2 concentration in blood greater than in alveolar air «prior to gas exchange» ✔
e. CO2 diffuses through wall of capillary and alveolus into alveolar airspace ✔
Examiners report
Weak knowledge of pneumocytes from many candidates and whilst many showed an understanding of gas exchange they failed to articulate it properly using the correct phrasing and terminology.
The command term was “explain”. Only a few candidates actually explained the process. Candidates gave very general responses without reference to diffusion or the correct concentration gradients. Very often diffusion was referred to in general for gas exchange and it was not linked to concentration gradients. Some students got max 2 for correct references to diffusion with reference to both gases. Students getting max 3 were able to include references to correct concentration gradients as well.
Syllabus sections
- 22M.1.SL.TZ2.27: Pressure changes inside the thorax cause the movement of air in and out of the lung alveoli...
- 17N.2.SL.TZ0.01c: State the disease severity group that has the highest range of plasma desmosines.
-
18M.3.HL.TZ1.2b:
Calculate the total volume of air inhaled during one minute during the highest velocity of the treadmill in this test, giving the units.
- 17N.2.SL.TZ0.01f: State the relationship between diffusion capacity and urine desmosines.
- 17N.2.HL.TZ0.01a: Outline the effect of hypoxia on body mass and erythrocyte percentage.
- 18N.3.HL.TZ0.1c: Suggest how the total lung volume at rest would differ for a patient with emphysema.
- 19M.1.HL.TZ1.23: What is produced by type II pneumocytes? A. Epinephrine B. Elastase C. Pulmonary...
- 18M.1.SL.TZ2.28: What is the role of type II pneumocytes? A. To carry out gas exchange B. To keep the...
- 18N.2.SL.TZ0.1f: Among 75-year-old lifelong non-smokers the percentage incidence of lung cancer was 0.01 %....
- 17M.1.HL.TZ2.34: The graph shows the ventilation rate and the oxygen consumption of a subject before, during...
- 17N.2.SL.TZ0.01a: State the level of COPD that has the lowest FEV.
- 16N.1.SL.TZ0.27: What is the purpose of pulmonary surfactant? A. Promotes capillary growthB. Decreases...
- 16N.1.SL.TZ0.28: Which conditions are correct for inspiration?
- 18M.3.SL.TZ2.3b: Describe how the mean tidal volume after exercise could be determined using the graph.
- 18N.3.SL.TZ0.2c: Suggest how the total lung volume at rest would differ for a patient with emphysema.
-
18M.2.SL.TZ1.6a:
Outline the role of the parts of an alveolus in a human lung.
-
17N.2.SL.TZ0.01d:
Evaluate which of the two biomarkers would be the most useful indicator of COPD severity.
- 22M.1.SL.TZ1.27: A cell from the lungs, observed under the microscope, contains a large number of secretory...
- 18N.2.SL.TZ0.1g: State two respiratory diseases, other than lung cancer, caused by smoking.
- 18M.3.HL.TZ1.2c: Compare and contrast the effect of increasing treadmill speed on the ventilation rate and...
- 17M.3.SL.TZ1.3a: Calculate the difference in ventilation rate between resting and exercising.
-
17N.2.HL.TZ0.01c:
Using the data presented in this question, explain the effect of hypoxia on the body.
- 21N.2.SL.TZ0.2c: Outline the action taken by the diaphragm during inhalation.
- 18N.3.SL.TZ0.2b: Explain the changes in ventilation after 35 seconds.
- 18N.2.SL.TZ0.1c: Evaluate the evidence provided by the data in the graphs for smoking as a cause of lung cancer.
- 18N.3.HL.TZ0.1a: Calculate the ventilation rate at rest, giving the units.
- 17M.3.SL.TZ1.3b: Explain the change in the tidal volume during exercise.
-
21M.2.SL.TZ1.7a:
Outline the process of inhalation.
- 18M.3.HL.TZ1.2a : State the apparatus used to measure the tidal volume.
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 17M.1.SL.TZ2.28: Where does gas exchange occur in the lungs? A. In type I pneumocytes B. In the...
- 18M.3.SL.TZ2.3c: Predict, with a reason, the effect of exercise on the rate of cell respiration.
- 18M.3.SL.TZ2.3a: Determine the ventilation rate after exercise.
- 21N.1.SL.TZ0.27: What occurs during inhalation?
-
20N.1.SL.TZ0.28:
The graph shows a spirometer trace of oxygen consumption when breathing at rest and during exercise.
[Source: Courtesy of Dr. Dafang Wang for his work at University of Utah.]
What explains the difference between the traces at regions X and Y on the graph?
A. At X, the internal intercostal muscles contract more than the external intercostal muscles.
B. At Y, the ribcage moves up and out more than at X.
C. At X, the diaphragm flattens more per breath than at Y.
D. At Y, the intercostal muscles contract more slowly than at X.
-
17N.2.HL.TZ0.01b:
Using the data in the graph, deduce whether hypoxia increases or decreases the endurance of the rats’ diaphragm muscle.
-
19M.3.SL.TZ2.3c:
Outline how ventilation rate could have been monitored in this study.
-
17N.2.SL.TZ0.01g:
Other studies on pulmonary diseases have shown a wide variety of results. Apart from age, sex and severity of COPD, list two other factors that may explain the inconsistent results between studies.
- 18M.3.SL.TZ2.3d: Identify a muscle responsible for increasing the volume of the chest cavity.
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
- 21M.1.HL.TZ1.21: Which process results in the exchange of gases across the membrane of pneumocytes? A. Active...
-
17N.2.SL.TZ0.01e:
Elastin is also an important component of other tissues such as arteries and ligaments. Evaluate how these other sources of elastin could affect the interpretation of the biomarker as an indicator of COPD.
- 21M.1.SL.TZ2.27: Which is an adaptation to increase rates of gas exchange in the lung? A. Small surface...
- 18N.3.HL.TZ0.1d: Outline the function of pneumocytes in the lungs.
- 19M.3.SL.TZ2.3b: Compare and contrast the effect of increasing exercise intensity at sea level and at an...
-
17N.2.SL.TZ0.01b:
Explain how a low FEV can be used to indicate emphysema.
- 17N.2.HL.TZ0.01e.i: Outline the effect of hypoxia on the force of contraction of the diaphragm.
-
17N.2.HL.TZ0.01f:
Using all relevant data in the question, evaluate the effectiveness of the rats’ adaptation to hypoxia.
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
- 19M.1.SL.TZ2.26: In premature babies born earlier than the 30th week of pregnancy, type II pneumocytes are...
-
21M.2.SL.TZ1.7b:
Explain the process of gas exchange taking place in the alveoli.
- 17N.1.HL.TZ0.23: Which type of cell is specialized to facilitate gas exchange? A. Type I pneumocytes B. Type...
- 18M.2.HL.TZ2.6b: Outline how ventilation in humans ensures a supply of oxygen.
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
-
17N.2.HL.TZ0.01e.ii:
Hypoxia caused a 13 % increase in the surface area to volume ratio of the diaphragm. Suggest a reason for this change.
- 18M.1.SL.TZ1.28: How are the insides of alveoli prevented from sticking together?
- 18N.2.SL.TZ0.1a: Calculate the change in the percentage of the male population that smoked from 1950 to 2000.
- 18N.2.SL.TZ0.1d: Describe the relationship between the incidence of lung cancer and stopping smoking.
- 18N.2.SL.TZ0.1b: Compare and contrast the trends in smoking behaviour between males and females between 1950...
- 18N.2.SL.TZ0.1e: Explain evidence from the data in the table that could be used to persuade a smoker to give...
- 18N.2.HL.TZ0.6c: Adult humans may absorb more than five hundred litres of oxygen per day. Explain how gas...
- 18N.3.HL.TZ0.1b: Explain the changes in ventilation after 35 seconds.
- 18N.3.SL.TZ0.2a: Calculate the ventilation rate at rest, giving the units.
- 19M.2.SL.TZ1.4a: Outline the functions of type I and type II pneumocytes.
-
17N.2.HL.TZ0.01d.ii:
Muscle fibres are stimulated to contract by the binding of acetylcholine to receptors in their membranes and the subsequent depolarization.
Suggest a reason for increasing the concentration of sodium–potassium pumps in the membranes of diaphragm muscle fibres.
-
17N.2.HL.TZ0.01g:
Discuss the advantages and disadvantages of using rats as models in this investigation.
- 19M.2.HL.TZ1.6a: Outline the process of inspiration in humans.
- 19M.3.SL.TZ2.3a: State one other variable that should have been controlled in this study.
- 19N.2.SL.TZ0.6c: Explain how ventilation and lung structure contribute to passive gas exchange.
- 21N.2.HL.TZ0.4c: Outline the action taken by the diaphragm during inhalation.
- 16N.2.SL.TZ0.6c: Describe what happens in alveoli.
- 19N.1.HL.TZ0.23: Which factors could cause emphysema? I. Air pollution II. Genetic predisposition III....
-
17N.2.HL.TZ0.01d.i:
Analyse the graph to obtain two conclusions about the concentration of sodium–potassium pumps.
-
17N.2.SL.TZ0.01h:
Discuss whether measurements of desmosine concentration would be useful for monitoring changes in the health of a patient.
- 21M.1.SL.TZ2.28: Where in the body are type I pneumocytes found? A. Alveoli B. Nephrons C. Capillaries D....
