1. Unit Overview – pages 138-139 The Life of a Cell Cellular Transport and the Cell Cycle Cellular Transport

2. For your consideration… 1.After eating a sugary or salty snack, why are you so thirsty? 2.Why do fingers wrinkle in the bathtub?

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

4. 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 Selectively permeable membrane

5. Label each tab. To return to the chapter summary click escape or close this document. Hypertonic Solution Isotonic Solution Hypotonic Solution

6. Section 8.1 Summary – pages 195 - 200 Most cells 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 the concentration of dissolved substances is lower in the solution outside the cell than the concentration in the cell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

11. Section 8.1 Summary – pages 195 - 200 Cells in a hypotonic solution So, water enters a cell by osmosis, increasing cell pressure (called turgor pressure) and causing the cell to swell. Plant cells swell beyond their normal size as pressure increases.

12. Red Blood Cells in Hypotonic Solution

13. Section 8.1 Summary – pages 195 - 200 Cells in a hypertonic solution In a hypertonic solution the concentration of dissolved substances outside the cell is higher than the concentration inside the cell. H2OH2O H2OH2O Water Molecule Dissolved Molecule

14. Section 8.1 Summary – pages 195 - 200 Cells in a hypertonic solution So, water leaves a cell by osmosis, causing the cell to shrink. Plant cells lose pressure as the plasma membrane shrinks away from the cell wall.

15. Red Blood Cells in Hypertonic Solution

16. Section 8.1 Summary – pages 195 - 200 Passive Transport Passive transport: movement of materials through a membrane that does not require the cell to used energy Facilitated diffusion: the passive transport of materials across the membrane using transport proteins.

17. Passive Transport

18. Section 8.1 Summary – pages 195 - 200 Passive Transport Some of the proteins form channels for the molecules to flow through with the concentration gradient. Carrier proteins change shape to allow a substance to pass through with the concentration gradient.

19. Section 8.1 Summary – pages 195 - 200 Active Transport Active transport: movement of materials through a membrane against a concentration gradient that requires energy from the cell Plasma membrane Concentration gradient Carrier proteins Cellular energy Step 1Step 2

20. Active Transport

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

22. 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

23. 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

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

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

26. Endocytosis & Exocytosis