2. 8.1 Section Objectives – page 195 Explain how the processes of diffusion, passive transport, and active transport occur and why they are important to cells. Section Objectives: Predict the effect of a hypotonic, hypertonic, or isotonic solution on a cell.

3. Section 8.1 Summary – pages 195 - 200 Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Osmosis: Diffusion of Water In a cell, water always moves to reach an equal concentration on both sides of the membrane.

4. Section 8.1 Summary – pages 195 - 200 The diffusion of water across a selectively permeable membrane is called osmosis. Osmosis: Diffusion of Water Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell.

5. Section 8.1 Summary – pages 195 - 200 Unequal distribution of particles, called a concentration gradient, is one factor that controls osmosis. What controls osmosis? Before Osmosis After Osmosis Water molecule Sugar molecule Selectivel y permeable membran e

6. Section 8.1 Summary – pages 195 - 200 Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions. Cells in an isotonic solution H2OH2O H2OH2O Water Molecule Dissolved Molecule

7. Section 8.1 Summary – pages 195 - 200 Cells in an isotonic solution In an isotonic solution, the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

8. Section 8.1 Summary – pages 195 - 200 Cells in an isotonic solution In an isotonic solution, water molecules move into and out of the cell at the same rate, and cells retain their normal shape. H2OH2O H2OH2O Water Molecule Dissolved Molecule

9. Section 8.1 Summary – pages 195 - 200 Cells in an isotonic solution A plant cell has its normal shape and pressure in an isotonic solution.

10. Section 8.1 Summary – pages 195 - 200 Cells in a hypotonic solution In a hypotonic solution, water enters a cell by osmosis, causing the cell to swell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

11. Section 8.1 Summary – pages 195 - 200 Cells in a hypotonic solution Plant cells swell beyond their normal size as pressure increases.

12. Section 8.1 Summary – pages 195 - 200 Cells in a hypertonic solution In a hypertonic solution, water leaves a cell by osmosis, causing the cell to shrink. H2OH2O H2OH2O Water Molecule Dissolved Molecule

13. Section 8.1 Summary – pages 195 - 200 Cells in a hypertonic solution Plant cells lose pressure as the plasma membrane shrinks away from the cell wall.

14. Section 8.1 Summary – pages 195 - 200 Passive Transport When a cell uses no energy to move particles across a membrane passive transport occurs. Concentration gradient Plasma membrane

15. Section 8.1 Summary – pages 195 - 200 Passive Transport by proteins Passive transport of materials across the membrane using transport proteins is called facilitated diffusion. Plasma membrane Channel proteins Concentration gradient

16. Section 8.1 Summary – pages 195 - 200 Passive Transport by proteins Some transport proteins, called channel proteins, form channels that allow specific molecules to flow through. Plasma membrane Channel proteins Concentration gradient

17. Section 8.1 Summary – pages 195 - 200 Passive transport by proteins The movement is with the concentration gradient, and requires no energy input from the cell. Concentration gradient Plasma membrane Step 1Step 2 Carrier proteins

18. Section 8.1 Summary – pages 195 - 200 Passive transport by proteins Carrier proteins change shape to allow a substance to pass through the plasma membrane. Concentration gradient Plasma membrane Step 1Step 2 Carrier proteins

19. Section 8.1 Summary – pages 195 - 200 Passive transport by proteins In facilitated diffusion by carrier protein, the movement is with the concentration gradient and requires no energy input from the cell. Plasma membrane Step 1Step 2 Carrier proteins Concentration gradient

20. Section 8.1 Summary – pages 195 - 200 Active Transport Movement of materials through a membrane against a concentration gradient is called active transport and requires energy from the cell. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

21. Section 8.1 Summary – pages 195 - 200 How active transport occurs In active transport, a transport protein called a carrier protein first binds with a particle of the substance to be transported. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

22. Section 8.1 Summary – pages 195 - 200 How active transport occurs Click image to view movie.

23. Section 8.1 Summary – pages 195 - 200 How active transport occurs Each type of carrier protein has a shape that fits a specific molecule or ion. Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

24. Section 8.1 Summary – pages 195 - 200 How active transport occurs When the proper molecule binds with the protein, chemical energy allows the cell to change the shape of the carrier protein so that the particle to be moved is released on the other side of the membrane. Step 1Step 2 Carrier proteins Cellular energy Plasma membrane Concentration gradient

25. Section 8.1 Summary – pages 195 - 200 How active transport occurs Once the particle is released, the protein’s original shape is restored. Step 1Step 2 Carrier proteins Cellular energy Plasma membrane Concentration gradient Active transport allows particle movement into or out of a cell against a concentration gradient.

26. Section 8.1 Summary – pages 195 - 200 How active transport occurs Click image to view movie.

27. Section 8.1 Summary – pages 195 - 200 Transport of Large Particles Endocytosis is a process by which a cell surrounds and takes in material from its environment. EndocytosisExocytosis Digestion Nucleus Wastes

28. Section 8.1 Summary – pages 195 - 200 Transport of Large Particles The material is engulfed and enclosed by a portion of the cell’s plasma membrane. Exocytosis Digestion Nucleus Wastes Endocytosis

29. Section 8.1 Summary – pages 195 - 200 Transport of Large Particles The resulting vacuole with its contents moves to the inside of the cell. Exocytosis Digestion Nucleus Wastes Endocytosis

30. Section 8.1 Summary – pages 195 - 200 Transport of Large Particles Exocytosis is the expulsion or secretion of materials from a cell. Endocytosis Exocytosis Digestion Nucleus Wastes

31. Section 8.1 Summary – pages 195 - 200 Transport of Large Particles Endocytosis and exocytosis both move masses of material and both require energy. Endocytosis Exocytosis Digestion Nucleus Wastes

32. Section 1 Check Question 1 B. endocytosis A. active transport The diffusion of water across a selectively permeable membrane is called __________. Water molecule Sugar molecule Selectively permeable membrane NC: 2.03

33. Section 1 Check Question 1 D. osmosis C. exocytosis The diffusion of water across a selectively permeable membrane is called __________. Water molecule Sugar molecule Selectively permeable membrane NC: 2.03

34. Section 1 Check The answer is D, osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within the cell. Water molecule Sugar molecule Selectively permeable membrane Before osmosisAfter osmosis NC: 2.03

35. Section 1 Check What is the expected result of having an animal cell in a hypertonic solution? Question 2 D. The cell retains its normal shape. C. The cell swells up. A. The cell shrivels up. B. The plasma membrane shrinks away from the cell wall. NC: 2.03

36. Section 1 Check The answer is A. In a hypertonic solution, cells experience osmosis of water out of the cell. Animal cells shrivel because of decreased pressure in the cells. H2OH2O H2OH2O Water molecule Sugar molecule NC: 2.03

37. Section 1 Check A grocer mists the celery display with water to keep it looking fresh. What type of solution is the celery now in? Question 3 D. exotonic C. hypertonic B. hypotonic A. isotonic

38. Section 1 Check The answer is B. Plant cells contain a rigid cell wall and do not burst even in a hypotonic solution.

39. Plasma membrane Section 1 Check Transport of materials across the plasma membrane that does not require energy from the cell but does use transport proteins is called __________. Question 4 B. simple diffusion A. osmosis Concentration gradient Channel proteins NC: 2.03

40. Section 1 Check Transport of materials across the plasma membrane that does not require energy from the cell but does use transport proteins is called __________. Question 4 D. active transport C. facilitated diffusion Plasma membrane Concentration gradient Channel proteins NC: 2.03

41. Section 1 Check The answer is C. Facilitated diffusion is a type of passive transport and requires no energy from the cell. Plasma membrane Concentration gradient Channel proteins NC: 2.03