CELLS

1. CELLS Revision Questions on diffusion Write down your answer before pressing the mouse to find the correct answer.

2. Give the definition of diffusion. 1. Answer: The natural movement of particles from an area of high particle concentration to an area of low particle concentration.

3. 2. Which of the examples below show diffusion? • The smell of air freshener spreading through a room • Air being pumped into a tyre • Smoke rising upwards in a non-smoky room • Leaking gas spreading through the air in a lab • Disappearing vapour trail from a jet aircraft This is diffusion This is diffusion This is diffusion

4. 3. List 3 substances which are able to diffuse into a cell. Answer ? • Glucose • Amino acids • Oxygen

5. 4. What substances can diffuse out of a cell. Answer • Carbon dioxide • Water • Urea

6. 5. Give the definition of osmosis. Answer The movement of water molecules from an area of high water molecule concentration to an area of low water molecule concentration across a selectively permeable membrane.

7. 6.6. If plant cells are placed in a 100% water solution, in what direction will the water move by osmosis? 100% water plant cell water moves into the cell by osmosis

8. 7. What name is given to describe a plant cell which is full of water that has entered by osmosis? Answer: Turgid cell wall cell membrane

9. What happens to red blood cells if they are placed in distilled water? 8. Answer: They burst !

10. 9. Why will a plant cell not burst if it is placed in distilled water? Answer: Because it has a rigid cell wall.

11. 9. What name is given to describe a plant cell which has lost a lot of water by osmosis? Answer: Flaccid vacuole cell membrane cell wall

12. 10. Describe the appearance of a potato cell after 30 minutes in strong sucrose solution. Answer: Vacuole is small Membrane has pulled away from cell wall.

13. 11. Look at the diagram below. Do the substances below move into or out of the cell? glucose oxygen carbon dioxide

14. 12. Look at the diagram below. visking tubing water glucose and starch solution • After 15 minutes, what has happened to the: • glucose molecules ? • starch molecules ? They pass out of the visking tubing into the water They remain in the visking tubing

15. 13. Why did the glucose molecules pass through the visking tubing? Glucose molecules are small enough to diffuse through the membrane. Why did the starch molecules not pass through the visking tubing? Starch molecules are too large to diffuse through the visking tubing membrane.

16. Multicellular organisms need special organs for diffusion of gases into and out of their bodies. 14. Where does this exchange of gases take place in mammals? Air sacs of the lungs.

17. 15. The inner wall of the air sac is lined with a layer of …………… . This is to allow the gases to ………….… and allow easier …………….. moisture dissolve diffusion

18. 16. Gases are exchanged between the cells of the leaves and the air by diffusion. Name the structures in the leaf through which the gases pass. Answer: Stomata

19. To investigate osmosis in plant cells the experiment below was set up. 17. A B strong salt solution water potato potato In which apparatus will the water enter the cell ? Apparatus B

20. 18. Why did the water enter the potato? A B strong salt solution water potato potato In osmosis water moves from a high concentration (the water) to a low concentration (in the potato cells).

21. 20. What do we call a membrane which only allows certain substances to pass through? Selectively permeable.

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