1. 4.1 Cell Membranes and Transport
KEY Concepts
How Does the Cell Membrane Help Maintain Homeostasis?
What is osmosis and how does it affect living organisms?
What is Difference between Passive and Active Transport?
Language/Vocab
Homeostasis
Diffusion
Osmosis
Active transport
Passive transport
Facilitated Diffusion

2. Homeostasis
Balance all organisms must maintain with their surrounding environment
What factors do humans have to regulate to maintain homeostasis?

3. Homeostasis
Individual cells maintain homeostasis by controlling what enters and exits the cell
What structure controls what enters and exits the cell?

4. The Cell Membrane Made of a bilayer of phospholipids
Phospholipids have a hydrophobic tail (water fearing) and hydrophilic head (water loving).
Proteins are embedded in the membrane to help move materials in-and-out of the cell.

5. The Cell Membrane
Why is the cell membrane called a fluid-mosiac?

6. The Cell Membrane
Cell membranes are SELECTIVELY PERMEABLE – what does this mean?
How is the strainer selectively permeable?

7. Passive vs. Active Transport
Passive transport:
Movement across a cell membrane that DOES NOT USE ENERGY
Moves molecules where they naturally want to go
Active transport:
Movement across a cell membrane that USES ENERGY
Forces molecules to move where they do not want to go

8. Diffusion
Movement of molecules through the cell membrane
Molecules move from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION
Passive transport
Why is this passive transport?

9. Diffusion What direction will the molecules move?
EQUILIBRIUM is reached when concentrations are equal on both sides of the cell membrane

10. Osmosis Diffusion of WATER molecules through the cell membrane
Water always diffuses from an area of LOW SOLUTE CONCENTRATION to an area of HIGH SOLUTE CONCENTRATION
Passive transport
What is a solute? A solvent?

11. Osmosis

12. Osmosis Hypotonic solution:
Solute concentration is lower on the outside of the cell than inside the cell.
Which direction will water move?

13. Osmosis Hypertonic solution:
Solute concentration is higher on the outside of the cell than inside the cell.
Which direction will water move?

14. Osmosis Isotonic solution:
Solute concentration is equal on both sides of the cell membrane.
Which direction will water move?

15. Osmosis and Plant Cells
Plant cells require a hypotonic environment so water moves into the cell and the cell swells
Swelling of the cell builds up turgor pressure
Why is turgor pressure important?

16. Osmosis and Plant Cells
Plant cells in hypertonic environments lose water and the cell shrivels up
Shriveling of the cell is called plasmolysis
Why is it important for plant cells to prevent plasmolysis?

17. Osmosis and Plant Cells
Which plant has plasmolysized cells and which as turgid cells?

18. Osmosis and Animal Cells
What would happen to animal cells in hypotonic and hypertonic environments?

19. Summary of Osmosis

20. Facilitated Diffusion
Movement of molecules in and out of the cell using a carrier protein
Molecules move from an area of HIGH CONCENTRATION to and area of LOW CONCENTRATION
Why would molecules need help from a carrier protein?

21. Facilitated Diffusion
How is facilitated diffusion different from simple diffusion?
How are they the same?

22. Active Transport
Movement of molecules across the cell membrane that requires energy.
Molecules move from an area of LOW CONCENTRATION to an area of HIGH CONCENTRATION.
Why does this require energy?

23. Active Transport
Which way will the molecules move in active transport?

24. Endocytosis Movement of large molecules into a cell by engulfment
Pinocytosis - engulfing a liquid (“Cell drinking”)
Phagocytosis - engulfing a solid (“Cell eating”)

25. Summary of Cell Transport