Transport Across The Membrane

1. Transport Across The Membrane Osmosis

2. Objectives of unit: • Explain passive transport mechanisms of diffusion and facilitated diffusion, including the role of channel and carrier proteins • Define the process of osmosis • Explain the process of active transport and the role of proteins and ATP • Explain the processes of endocytosis and exocytosis • Describe the properties of gas exchange surfaces in living organisms • Explain how the structure of the mammalian lung is adapted for rapid gaseous exchange

3. What can you remember about osmosis fro IGCSE/GCSE? (convert pointer to pen tool by right clicking) Osmosis

4. The diffusion of solvent molecules, such as water, is known as osmosis water Solvent molecules e.g. water glucose Solute molecules e.g.glucose Water is the solvent used in nature

5. The definition of osmosis is: Osmosisis the net movement of solvent molecules from a region of their high concentration to one of their low concentration across a partially permeable membrane

6. Question 1: Complete the definition Osmosisis the net movement of solvent molecules from a region of their high concentration to one of their low concentration across a partially permeable membrane answer

7. Osmotic concentration relates to the amount of dissolved solutes in a solution high osmotic concentration low osmotic concentration (concentrated) (dilute) Insoluble molecules do not affect the osmotic concentration

8. Water molecules will move down their concentration gradient

9. Partially permeable membranes only let water and very small molecules through A partially permeable membrane results in an uneven distribution across the membrane Low osmotic concentration: A dilute solution with a high water potential High osmotic concentration: A concentrated solution with a low water potential

10. Which way will osmosis occur? NET osmosis water glucose high osmotic concentration low osmotic concentration partially permeable membrane

11. Osmosis can be modelled using an osmometer Water molecules enter the tubing by osmosis Water molecules leaves the tubing by osmosis 30 minutes later 30 minutes later Sucrose solution Pure water Sucrose solution Pure water

12. Question 2: An osmometer was used to investigate the affect of temperature on osmosis: • Calculate the averages and plot a graph to illustrate the affect of temperature on the rate of osmosis. • Explain the results. answer

13. Isotonic solutions have the same osmotic concentration as the cytoplasm of the cell external solution blood cell No NET osmosis Cell just not change

14. Hypertonic solutions have a higher osmotic concentration than the cytoplasm of the cell external solution blood cell NET osmosis out of the cell Causes animal cells to shrink

15. Hypotonic solutions have a lower osmotic concentration than the cytoplasm of the cell external solution blood cell NET osmosis into the cell Can cause animal cells to burst

16. Question 3: Match the terms with the definitions isotonic lower concentration than cell cytoplasm hypotonic higher concentration than cell cytoplasm hypertonic Same concentration as cell cytoplasm answer

17. Question 4: A scientist placed some red blood cells in a solution and viewed the cells with a light microscope. After a few minutes she noticed that many of the cells burst. Explain why this may have occurred. answer

18. Osmosis in red onion cells Hypertonic solution Hypotonic solution Isotonic solution osmosis osmosis osmosis Incipient plasmolysis Full plasmolysis Turgor Causes a plant to wilt Cell wall exerts an inward pressure

19. Question 5: Match the label to the solution B A C 1. Isotonic solution 2. hypertonic solution 3. hypotonic solution answer

20. Question 6: Predict, with reasons, what will happen to the flowers in the diagram below: very salty water answer

21. Summary: • Keywords you need to know the meaning of: • Osmosis • Partially permeable membrane • Isotonic • Hypertonic • Hypotonic • Turgor • Plasmolysis

22. Activity • Read pages 106 – 107 • Make brief notes • Answer questions 1 and 2 on page 107

23. End www.clickbiology.com Answers to questions

24. Question 1 answer Osmosisis the net movement of solvent molecules from a region of their high concentration to one of their low concentration across a partially permeable membrane

25. Question 2 answer 20 18 16 14 12 10 8 6 4 2 x x x Rate of osmosis mm/min x x x 10 20 30 40 50 Temperature/oC With increasing temperature the water molecules gain kinetic energy; Increasing the rate of osmosis

26. Question 3 answer isotonic lower concentration than cell cytoplasm hypotonic higher concentration than cell cytoplasm hypertonic same concentration as cell cytoplasm

27. Question 4 answer The solution was hypertonic; So water entered the cells; By osmosis; Causing them to swell and burst

28. Question 5 answer 2 B 3 A 1 C 1. Isotonic solution 2. hypertonic solution 3. hypotonic solution

29. Question 6 answer The salty water is hypertonic; As it has a higher osmotic concentration than the cell cytoplasm; So water leaves the cells of the stems; By osmosis; Causing the cells to plasmolyse; And the flowers to wilt;

30. END www.clickbiology.com