Gas exchange and breathingIB MYP Sciences: Subtopic test

1. 1
   A museum in Cape Town has an interactive display that follows the path of air as a visitor breathes in. The display labels the structures that air passes through and the muscles and bones that move when we breathe.

   (a)

   Which row shows the correct order of the structures that air passes through when a person breathes in?

   [1 mark]

   • ABronchi, trachea, bronchioles, alveoli
   • BTrachea, bronchi, bronchioles, alveoli
   • CTrachea, bronchioles, bronchi, alveoli
   • DBronchioles, bronchi, trachea, alveoli

   (b)

   Which structure is a dome-shaped sheet of muscle that flattens and moves downwards when a person breathes in?

   [1 mark]

   • AIntercostal muscles
   • BBronchus
   • CAlveolus
   • DDiaphragm

   (c)

   Describe two functions of the ribcage in the respiratory system.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In the lungs, oxygen moves from the air into the blood and carbon dioxide moves from the blood into the air. This happens in the alveoli, tiny air sacs that are each surrounded by a network of capillaries.

   (a)

   Which process moves oxygen from the air in an alveolus into the blood?

   [1 mark]

   • ADiffusion
   • BOsmosis
   • CDigestion
   • DVentilation

   (b)

   Compared with the air in the alveoli, how is the blood that arrives at the lungs different?

   [1 mark]

   • AIt has more oxygen and more carbon dioxide
   • BIt has more oxygen and less carbon dioxide
   • CIt has less oxygen and more carbon dioxide
   • DIt has less oxygen and less carbon dioxide

   (c)

   Explain why oxygen diffuses from the alveoli into the blood.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student in Mumbai wants to find out how surface area affects how quickly substances diffuse, as a model of the alveoli. She cuts three identical 2 cm cubes of agar jelly containing alkali and a pink indicator. She leaves one cube whole, cuts one into 8 equal pieces and cuts one into 27 equal pieces. She places each set in the same volume of dilute hydrochloric acid at 20 °C and times how long it takes for all the pink colour to disappear as the acid diffuses in. The whole cube took 420 s, the 8 pieces took 200 s and the 27 pieces took 135 s.

   (a)

   Identify the independent variable, the dependent variable and one control variable in the student's investigation.

   [3 marks]

   (b)

   Describe the trend in the results and explain how the investigation helps to explain why the lungs contain millions of alveoli.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   At the summit of Mount Everest the air still contains about 21% oxygen, but the air pressure is only about one third of that at sea level, so each breath delivers much less oxygen to the lungs. Many climbers breathe oxygen from cylinders. Thousands of empty cylinders have been left on the mountain, and local guides carry the heavy cylinders at great personal risk.

   (a)

   Describe the pathway taken by oxygen from the air to the blood of a climber, and explain how the alveoli are adapted for gas exchange.

   [6 marks]

   (b)

   Discuss the social, economic and environmental implications of climbers using supplementary oxygen on Mount Everest, and justify a conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions