Osmosis and active transportIB MYP Biology: Subtopic test

1. 1
   The lungs contain millions of tiny air sacs called alveoli. Oxygen in the air inside each alveolus moves into the blood in the capillaries that surround it. During a race a runner in Nairobi breathes deeper and faster and her heart beats faster.

   (a)

   Which term describes the net movement of oxygen from the air in the alveoli into the blood?

   [1 mark]

   • AOsmosis
   • BActive transport
   • CFiltration
   • DDiffusion

   (b)

   Which feature of the alveoli increases the rate of diffusion of oxygen?

   [1 mark]

   • AA thick wall of several layers of cells
   • BA very large total surface area
   • CA poor blood supply
   • DAir that contains no oxygen

   (c)

   Explain why deeper breathing and a faster heartbeat increase the rate at which oxygen enters her blood.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Cape Town investigates osmosis in potato. She cuts five potato cylinders of the same length, each with a mass of 3.0 g. She places one cylinder in each of five beakers containing sugar solution of concentration 0.0, 0.2, 0.4, 0.6 and 0.8 mol dm⁻³. After 24 hours she blots each cylinder dry and weighs it again. The changes in mass were +0.4 g, +0.2 g, 0.0 g, −0.3 g and −0.5 g, in the same order as the concentrations.

   (a)

   What is the independent variable in this investigation?

   [1 mark]

   • AThe concentration of the sugar solution
   • BThe change in mass of the cylinder
   • CThe length of the cylinder
   • DThe time left in the solution

   (b)

   Which concentration of sugar solution is closest to the concentration of the liquid inside the potato cells?

   [1 mark]

   • A0.0 mol dm⁻³
   • B0.2 mol dm⁻³
   • C0.4 mol dm⁻³
   • D0.8 mol dm⁻³

   (c)

   Explain why the potato cylinder in the 0.8 mol dm⁻³ solution lost mass.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Tomato plants grown on a farm in southern Spain begin to wilt after the irrigation water becomes very salty. The farmer also finds that the root hair cells of healthy plants take up nitrate ions from the soil, even though the concentration of nitrate in the soil is lower than the concentration inside the root hair cells.

   (a)

   Explain why the tomato plants wilt when watered with very salty water.

   [3 marks]

   (b)

   Explain how the root hair cells take up nitrate ions from the soil even though the nitrate concentration in the soil is lower than inside the cells.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In countries with cold winters, such as Canada, local councils spread large amounts of salt on roads to melt ice. Rain and melting snow wash some of the salt into the soil beside the road and into nearby streams. Councils must decide how much salt to use each year.

   (a)

   Explain, using ideas about osmosis, how salt washed into the soil beside a road can damage grass and trees.

   [6 marks]

   (b)

   Discuss and evaluate the use of large amounts of road salt to keep roads clear of ice.

   [6 marks]

   Total for question 4: 12 marks

End of questions