Question 1
What is the function of the pleural membranes?
- They make mucus to trap dust
- They allow the lungs to move with little friction
- They carry oxygen to the alveoli
- They keep the trachea open
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Answer: B (1)
Question 2
Name the structure of the thorax that: (a) is a sheet of muscle under the lungs; (b) carries air from the trachea into each lung; (c) are the tiny air sacs where gas exchange takes place.
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- (a) diaphragm (1)
- (b) bronchus / bronchi (1)
- (c) alveoli (1)
Question 3
Explain how the intercostal muscles and the diaphragm cause air to enter the lungs.
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- intercostal muscles contract, so ribs move up and out (1)
- diaphragm contracts and flattens (1)
- volume of the thorax increases (1)
- pressure in the thorax decreases (below atmospheric pressure) so air moves in (1)
Question 4
Explain how two features of the alveoli make gas exchange efficient.
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- walls one cell thick (1) giving a short diffusion distance (1)
- many alveoli (1) giving a large surface area (1)
- good blood supply / many capillaries (1) maintains a steep concentration gradient (1)
- moist lining (1) so gases can dissolve (1)
- Max 4
Question 5
A student counts 15 breaths in one minute at rest. Straight after exercise she counts 42 breaths in two minutes. Calculate the percentage increase in her breathing rate after exercise.
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- breathing rate after exercise = 42 ÷ 2 = 21 breaths per minute (1)
- increase = 21 − 15 = 6 (1)
- percentage increase = 6 ÷ 15 × 100 = 40% (1)
- allow full marks for the correct answer with no working
Question 6
A student breathes out through limewater before and after exercise. The limewater turns cloudy faster after exercise. Explain this result.
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- limewater turns cloudy when carbon dioxide is present (1)
- exercising muscles respire faster / more respiration (1)
- so more carbon dioxide is produced and breathed out (1)
Question 7
Describe and explain the effects of smoking on the lungs and the circulatory system.
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| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | Describes and explains effects on both the lungs and the circulatory system, naming the harmful substances and linking each to its effect, including coronary heart disease. |
| 2 | 3–4 | Describes effects on both systems with some explanation, or explains several effects on one system, with some named substances. |
| 1 | 1–2 | Gives simple statements, such as smoking causes lung cancer or heart disease, with little explanation. |
Indicative content
- tar damages / destroys cilia, so mucus and bacteria are not removed, causing infections and bronchitis
- tar contains carcinogens that cause lung cancer
- emphysema: alveoli walls break down, reducing the surface area for gas exchange, so breathlessness
- carbon monoxide combines with haemoglobin, so red blood cells carry less oxygen
- heart has to work harder to deliver oxygen
- nicotine increases heart rate and blood pressure
- chemicals in smoke damage artery walls, so fatty deposits build up / blood clots form more easily
- coronary arteries become narrowed by fatty deposits, so less blood to the heart muscle, causing coronary heart disease and heart attack