7: Gas Exchange in Humans - Problems Flashcards
Describe how the inner wall in the human bronchus carries out its functions. (4)
The layer contains mucus-secreting cells.
These cells secrete mucus to trap dust particles and microorganisms in the inhaled air.
The layer also contains ciliated epithelial cells.
The cilia on the ciliated epithelial cells beat to sweep the mucus towards the pharynx.
In vigorous exercise, the smooth muscles of the bronchi relax. Explain the importance of this change. (3)
When the smooth muscles relax, the diameter of the lumen of the bronchus increases.
A larger volume of air can enter the lungs for gas exchange and be removed from the lungs after gas exchange,
so that more oxygen can be transported to muscle cells for respiration and more carbon dioxide produced by respiration during vigorous exercise can be removed from respiring cells.
(CE 2008 I Q3)
The following diagram shows part of the human respiratory system.
Name structure X and describe its function.
X is the pleural membrane,
it secretes pleural fluid to
reduce friction in breathing movement.
(CE 2008 I Q3)
Construct a flow chart to show the path of air passing from the atmosphere to the air sacs of the lungs.
Nasal cavity -> pharynx -> larynx -> trachea -> bronchus -> bronchiole -> air sac.
(CE 2008 I Q3)
The following diagram shows part of the human respiratory system.
In an asthma attack, structure Y constricts and the patient has breathing difficulty. Explain the effect of asthma on the rate of removal of carbon dioxide from the blood of the lungs. (4+1)
Volume of the inspired air decreases,
Less fresh air mixes with the residual air, thus concentration of carbon dioxide in the air sacs remains relatively high.
The concentration gradient of carbon dioxide between the alveolar air and the blood becomes smaller.
The rate of removal of carbon dioxide from blood decreases.
OR
Volume of the expired air decreases, carbon dioxide removed from air sacs to atmosphere decreases, thus concentration of carbon dioxide inside the lungs remains relatively high,
The concentration gradient of carbon dioxide between the alveolar air and the blood becomes smaller
The rate of removal of carbon dioxide from blood decreases.
The table below shows the change in the level of oxygen in the air at sea level and at high altitude and how it affects a person’s rate of breathing.
key: (sea level, high altitude)
Level of oxygen in air: (higher, lower)
Rate of breathing: (lower, higher)
Using information from the table, explain why the person felt tired when they travelled from sea level to high altitude. (4)
The level of oxygen in the air at high altitude was lower than that at sea level.
The concentration gradient of oxygen between the air in the air sacs and the blood in the capillaries was less steep at high altitude.
Therefore, oxygen diffused across the walls of air sacs and capillaries into the blood more slowly.
As a result, less oxygen was transported by the red blood cells to the body cells for respiration. Hence, the person felt tired.
The table below shows the change in the level of oxygen in the air at sea level and at high altitude and how it affects a person’s rate of breathing.
key: (sea level, high altitude)
Level of oxygen in air: (higher, lower)
Rate of breathing: (lower, higher)
Suggest why it is important for a person to breathe at a higher rate at high altitude. (2)
A higher rate of breathing increases the volume of air inhaled per unit time,
so that the concentration gradient of oxygen between the air sacs and the capillaries can be maintained / more oxygen is available for gas exchange.
The table below shows the change in the level of oxygen in the air at sea level and at high altitude and how it affects a person’s rate of breathing.
key: (sea level, high altitude)
Level of oxygen in air: (higher, lower)
Rate of breathing: (lower, higher)
Suggest the importance of producing more red blood cells at high altitude. (1)
The production of more red blood cells increases the oxygen-carrying capacity of blood.
(CE 2005 I Q4)
The photomicrograph below shows a section of a mammalian lung.
With reference to two features observable in the photomicrograph, explain how the lung tissue is adapted for gas exchange. (4)
(choose any 2)
1. The wall of A is very thin,
so as to reduce the distance of diffusion of respiratory gases.
2. A is richly supplied with blood capillaries, which allows a rapid transport of gas to and away the air sacs, maintaining a steep concentration gradient of gases between A and the blood.
3. The lung tissue is made up of numerous air sacs,
so there is a large surface area for diffusion of gases to take place.
(CE 2005 I Q4)
The photomicrograph below shows a section of a mammalian lung.
Oxygen moves continuously from the air in A into the capillaries. However, the oxygen content in A remains relatively high. Explain how this is achieved. (2)
During ventilation, some air in the lungs is replaced by fresh air, which contains a high oxygen content.
(CE 2005 I Q4)
Describe how to compare the oxygen content of samples of atmospheric air and exhaled air, stored in two gas jars. (2)
Put a burning candle in the two jars and compare the time the candle can burn.
(DSE 2017 IB Q5)
Briefly describe the breathing actions that bring air into the lungs. (4)
Intercostal muscle contracts to result in upward and outward movement of rib cage / raise the rib cage.
Diaphragm muscle contracts to flatten the diaphragm;
both actions increase the volume of the thoracic cavity.
As a result, the pressure inside the lungs drops below atmospheric pressure,
hence air is forced into the lungs.
(DSE 2017 IB Q5)
Diagram I shows some structures of a human lung while diagram II shows a collapsed lung ruptured at location Y.
Explain why the lung collapses if it is ruptured at location Y.
Air will leak into the pleural cavity
from outside through the lungs / the negative pressure of pleural cavity cannot be maintained.
The lung collapses due to its own elasticity.
(DSE 2019 IB Q5)
Diagram L below shows part of the lung in a patient suffering from a certain lung disease. A hardened layer of dust deposit was found on the respiratory surface of the air sacs. Photomicrograph M shows the lung tissue taken from the patient.
Compare and explain the oxygen and glucose content of the blood in vessels A and B. (4)
A contains more oxygen than B / B contains less oxygen than A
This is because gas exchange takes place at air sacs where oxygen is taken up by blood through diffusion,
so blood leaving the air sac should have more oxygen.
A contains less glucose than B / B contains more glucose than A.
This is because the cells in air sacs / lung tissues have taken up glucose from the blood for respiration,
so blood leaving air sac should have less glucose.
(DSE 2019 IB Q5)
Diagram L below shows part of the lung in a patient suffering from a certain lung disease. A hardened layer of dust deposit was found on the respiratory surface of the air sacs. Photomicrograph M shows the lung tissue taken from the patient.
With reference to the above information about the lung disease, suggest two possible ways in which the disease adversely affects gas exchange in the patient. (4)
- Dust deposits on the inner surface of the air sacs form a barrier,
which increases the diffusion distance, hence ;lowering the rate of gas diffusion from the air sacs to the blood. - The inner surface of the air sacs was covered by dust, thus the area available for diffusion was reduced.
- The hardened layer of dust deposit reduces the elasticity of the respiratory surfaces of the air sacs, hence there is a smaller maximum lung volume when the lung inflates.
