1. Diffusion, Osmosis and Active Transport
Homeostasis
Diffusion, Osmosis and Active Transport

2. Homeostasis
The process by which an organism maintains a constant internal environment despite the variations in the external environment
Ex. Your body stays at 98.6 degrees Fahrenheit even though the temperature outside changes.

3. Interest Grabber
In or Out?
Section 7-3
How is a window screen similar to a cell membrane? Read on to find out.
1. What are some things that can pass through a window screen?
2. What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen?
3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?

4. Cell Membrane
Lipid bilayer = gives the cell a flexible structure that forms a strong barrier between the cell and its surroundings.
Proteins = form channels and pumps that help move material across the membrane.
Carbohydrate chains = chemical identifiers, help cells to indentify other cells.

5. The Structure of the Cell Membrane
Section 7-3
Outside
of cell
Inside
(cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains

6. Homeostasis, Diffusion, and Osmosis
Homeostasis is the maintenance of a stable internal state within an organism. Examples of homeostasis in our bodies are:
Regulation of water content
Regulation of body temperature
Regulation of blood glucose levels
Hopefully students will mention water content. Growth, getting nutrients, getting rid of wastes

7. Concentration The mass of solute in a given volume of solution
Which has a higher concentration?
12 grams of salt in 3 liters of water
12 grams of salt in 6 liters of water

8. Diffusion
The spontaneous movement of particles from an area of higher concentration to an area of lower concentration.

10. Transportation of molecules in plant cells: Osmosis
The diffusion of water through a selectively permeable membrane.
Right click on web site and click on Open Hyperlink. Play all three

11. Figure 7-15 Osmosis
Section 7-3

12. Types of Solutions
Isotonic = concentrations of water and solute are the same on both sides of the membrane.
Hypertonic = more concentrated solution (water moves in)
Hypotonic = less concentrated solution (water moves out)

14. Evaluation: Osmosis
Think about what happens to the skin on your hands and toes after soaking in water or going swimming.
(Osmosis)
Next slide:

15. Evaluation: answer a or b Osmosis
1. Place your hand in salt water. What happens to the cells of the skin?
A. Wrinkled hands B. Smooth hands OR
A. Wrinkled hands B. smooth hands

16. Evaluation: answer a, b, or c Osmosis
2. Cells placed in pure distilled water without any minerals will:
A. Remain normal
B. CELLS SWELL AND BURST B. C.

17. Evaluation: answer a or b Osmosis
Predict what will happen to the cells of the fish.
3. Place a salt water fish from the Gulf of Mexico into an aquarium of fresh water.
A. Fish cells swell and burst B. Fish cells lose water and dehydrate OR
A. Dead fish because the cells lysed or burst from too much water.

18. 4. Describe the transportation of molecules in these slides of onion cells.

19. Facilitated Diffusion
Molecules that cannot diffuse across the cell membrane’s lipid bilayer on their own move through protein channels instead.

20. Facilitated Diffusion
Section 7-3
Glucose
molecules
High
Concentration
Cell
Membrane
Protein
channel
Low
Concentration

21. Active Transport
Movement of materials from low concentrations to a higher concentration.
Requires energy
Carried out by transport proteins (pumps) found in the membrane.
Diffusion and osmosis are passive transport. Do not need energy.

22. Active Transport Section 7-3 Molecule to be carried Energy Molecule
being carried
Energy

24. Bulk Transport
Endocytosis = process of taking material into the cell by means of infoldings, or pockets, of the cell membrane (forms a vacuole in the cell)
Phagocytosis – cytoplasm surrounds and engulfs large particles
Pinocytosis – cell takes in liquid from the surrounding environment

25. Bulk Transport
Exocytosis = the membrane of the vacoule fuses with the cell membrane, forcing the contents out of the cell.