IGCSE Biology | Practice Test | 25 Questions
State the three features of a gas exchange surface in humans.
Name the gas that makes up approximately 78% of atmospheric air.
State the approximate percentage of oxygen in atmospheric air.
Name the tiny air sacs found at the ends of the bronchioles, where gas exchange takes place.
Name the dome-shaped muscle found below the lungs that plays a role in breathing.
State what happens to the shape of the diaphragm when it contracts during inhalation.
State one difference between inspired air and expired air in terms of carbon dioxide.
Name the specialised cells in the lining of the airways that produce mucus.
State the function of cilia on ciliated cells in the trachea and bronchi.
State two changes in breathing that occur during vigorous physical activity.
Explain why the alveoli are efficient gas exchange surfaces. Refer to two structural features in your answer.
A student blows expired air through a straw into limewater (a solution that turns milky when CO₂ is present). The limewater turns milky within a few seconds. Explain why expired air causes this reaction, but atmospheric air would take much longer to produce the same result.
Explain why expired air contains more water vapour than inspired air.
Describe what happens to the diaphragm and external intercostal muscles during inhalation, and explain how these changes cause air to move into the lungs.
During a normal resting exhalation, the diaphragm and external intercostal muscles relax. Explain how this causes air to leave the lungs. Refer to volume and pressure in your answer.
A student runs a 400 m race. After finishing, her breathing has changed compared to when she was at rest.
(a) State two changes in her breathing.
(b) Explain why each change is needed.
Explain why the alveolus wall being only one cell thick is important for efficient gas exchange.
Explain why a good blood supply around the alveoli is important for maintaining a high rate of gas exchange.
A patient has a condition where their goblet cells do not produce enough mucus. Explain the consequences of this for the gas exchange system.
The table below shows the approximate composition of inspired and expired air.
| Gas | Inspired air | Expired air |
|---|---|---|
| Oxygen | 21% | 16% |
| Carbon dioxide | 0.04% | 4% |
| Nitrogen | 78% | 78% |
(a) By how many percentage points has the oxygen content decreased from inspired to expired air?
(b) State the carbon dioxide percentage in expired air.
(c) Explain why expired air contains less oxygen than inspired air.
The alveoli are the site of gas exchange in the lungs.
(a) State three structural characteristics of the alveoli that make them an efficient gas exchange surface.
(b) Explain why oxygen diffuses from the alveolus into the blood, and not in the opposite direction.
(c) Explain why the constant flow of blood through the capillaries surrounding the alveolus is important for maintaining a high rate of diffusion.
The breathing mechanism involves changes to the thorax.
(a) Describe the role of the diaphragm, external intercostal muscles, and ribs during inhalation. Explain how these changes cause air to enter the lungs.
(b) Describe what happens during a normal resting exhalation, and explain how air leaves the lungs.
(c) During vigorous exercise, exhalation becomes more forceful. Name the muscles responsible and explain how they produce a greater pressure change.
A student investigates the differences between inspired and expired air using three tests.
(a) The student breathes expired air onto a cold glass surface, and fans atmospheric air onto a second cold glass surface of the same temperature. Predict and explain which glass surface will show more condensation.
(b) The student measures the temperature of both air samples. State which sample would be warmer and explain why.
(c) The percentage of nitrogen is approximately 78% in both inspired and expired air. Explain why nitrogen stays the same while oxygen and carbon dioxide percentages change.
The trachea and bronchi contain specialised cells that protect the gas exchange system.
(a) Name the two types of specialised cell found in the lining of the trachea and bronchi.
(b) Describe how these two cell types work together to prevent pathogens and particles from reaching the alveoli.
(c) A person develops a condition in which their ciliated cells permanently stop beating. Explain the consequences for their gas exchange system, referring to both cell types named in (a).
Explain how the structure of the human gas exchange system makes it efficient at exchanging gases between the air and the blood.
In your answer, you must refer to:
- The structure of the alveoli
- The role of breathing movements
- One other structural feature of the gas exchange system
Write your answer in full sentences.
