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Biology journal Cambridge IGCSE 0610

Pupil sheet · Diffusion and active transport

Diffusion in living things — questions

Name ______________________ Date ____________

Try every question before you use a nudge. Write in full sentences where you are asked to explain.

1. state

How does oxygen get into a respiring cell?

Circle one answer.

  • By active transport, using energy
  • Through holes in the cell wall only
  • By diffusion through the cell membrane, down its concentration gradient
  • It is made inside the cell

Nudge (only if you are stuck): The cell keeps using oxygen up. Where is the concentration higher: inside or outside?

2. state

Match each substance to where it diffuses in an organism.

Write the number of the matching option.

  1. From the air in the lungs into the blood
  2. From the air into a leaf through the stomata
  3. From the small intestine into the blood
  4. From cells into the blood
  • Oxygen: ______
  • Carbon dioxide: ______
  • Glucose: ______
  • Urea: ______

Nudge (only if you are stuck): Think about lungs, leaves, the gut and respiring cells.

3. explain

The walls of the air sacs in the lungs and of the capillaries around them are each only one cell thick. Explain how this helps gas exchange.

Nudge (only if you are stuck): Which factor from the agar cubes does a thin wall change?

4. explain

Blood flows past the air sacs all the time and carries oxygen away. Explain why this keeps oxygen diffusing into the blood.

Nudge (only if you are stuck): What happens to the concentration gradient if oxygen is carried away?

5. explain

After a meal, the concentration of glucose in the small intestine is higher than in the blood. Explain how glucose reaches the blood, and why it matters that glucose dissolves in water.

Nudge (only if you are stuck): Which way is the concentration gradient? What has to happen to a substance before its particles can move through water and membranes?

6. suggest

A fish takes in oxygen through its gills. Water flows over the gills in one direction and blood flows through them in the opposite direction. Suggest two features the gills need for fast diffusion of oxygen into the blood, using what you know about the lungs.

Nudge (only if you are stuck): Think of the four factors: surface area, distance, gradient, temperature.