1. Cell Membranes and Transport Go to Section:

2. About Cell Membranes 1.All cells have a cell membrane 2.Functions: a.Regulates what enters and exits the cell b.Provides protection for the cell c.Supports the cell Slide # 2 TEM picture of a real cell membrane.

3. 1. phospholipid bi-layer (2 membranes) a.Phosphate head is polar (water loving) b.Fatty acid tails non-polar (water fearing) c.Proteins embedded in membrane Structure of cell membrane Slide # 3

4. Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Slide # 4 Structure of the Cell Membrane Cell membrane has pores (holes) in it a.Selectively permeable: Allows some molecules in and keeps other molecules out b.Structure is related to its function!

5. Types of Passive Transport 1. Diffusion: molecules move from area of high concentration to area of lower concentration a.Occurs in living & non- living things b.Passive transport c.Does not use energy for it to occur Slide # 6 Diffusion continues until all molecules are evenly spaced

6. Types of Passive Transport 2. Facilitated diffusion: movement of specific molecules (glucose) across cell membranes through protein channels a.Protein channels are specific – only allow certain molecules across b.Passive – does not use energy to move glucose c.Movement occurs from high to lower concentration Slide # 7 Facilitated diffusion Diffusion

7. High Concentration Low Concentration Glucose molecules Cell Membrane Protein channel Slide # 7 Facilitated Diffusion Go to Section: Molecules move through a protein channel from high to lower concentration

8. Types of Passive Transport 3.Osmosis: movement of water from area of high concentration to area of lower concentration a.Diffusion of water b.Occurs in living & non- living things c.Passive – does not use energy Slide # 9 Water moves freely through pores. Solute (green) too large to move across.

9. Hypotonic Solution Slide # 10 Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (lyses)!

10. Hypertonic Solution Slide # 11 Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. Result: Water moves from inside the cell into the solution: Cell shrinks! (Plasmolysis)

11. Isotonic Solution Slide # 12 Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size!

12. Protecting Against Osmotic Pressure 1. Bacteria and plant cells have cell walls to prevent the cell from expanding and bursting when placed in a hypotonic solution. Plants use osmotic pressure turgor pressure to keep from wilting. 2. Single celled eukaryotes (paramecium, amoeba) use a contractile vacuole to pump excess water out of their cells to keep from bursting open. 3. Salt water fish have specialized salt-pumping cells so they will not dehydrate in their salt water ocean, which is hypertonic to their cells. 4. Our cells are constantly bathed in blood (isotonic). Our lungs and kidneys get rid of excess water in our body so our blood can always be isotonic to the rest of our cells.

13. Types of Active Transport 1. Active transport: movement of molecules from area of lower to higher concentration a.Movement against a concentration gradient b.Requires energy from the cell Slide # 13 Protein changes shape to move molecules: this requires energy!

14. Types of Active Transport 2. Endocytosis: taking material into a cell a.Cell membrane in-folds around food particle b.“cell eating” c.forms food vacuole & digests food d.This is how white blood cells eat bacteria! e.Uses energy Slide # 14

15. Types of Active Transport 3. Exocytosis: membrane surrounding the material fuses with cell membrane a.Forces material out of cell b.Cell changes shape – requires energy c.EX: Hormones exported from cell Slide # 15

16. Cell Membrane: Just Passing Through Slide # 13