1. Transport of Molecules and Homeostasis
Cell Structure and Function
Station 3
Transport of Molecules and Homeostasis

2. Essential Question
Why should a freshwater fish never be placed in a saltwater aquarium?
Most freshwater fish do not have the mechanisms necessary to adjust to the high levels of salt, so the salt would cause their cells to shrivel and die.

3. Pre-Preview Questions
The diffusion of water molecules in and out of cells is called?
Cyclosis
Osmosis
Active transport
Homeostasis

4. Pre-Preview Questions
A red blood cell placed in distilled water will swell and burst due to the diffusion
of ?
Salts from the cell to the water.
Water into the red blood cell.
Water from the blood cell into it’s environment.
Salts from the water into the red blood cell.

5. Pre-Preview Questions
What would happen if you watered a plant with salt water?
The cells would shrivel and pull away from the cell wall.
The blood cells would lyse (burst) and break the cell wall.
The plant would be rehydrated.
The plant would grow faster.

6. Copy the table into your journal and fill in the data.

7. 2. Using the information recorded in the data tables, draw the beakers, potatoes, and arrows showing which way the water would be going.
Solution A Solution B Solution C 25 g. sugar g. sugar distilled water
3. Determine which beaker contains a hypertonic solution, which contains a hypotonic solution, and which contains an isotonic solution.

8. 2. Using the information recorded in the data tables, draw arrows on the beakers below to illustrate what happened to the potato cores in each of the different solutions.
Solution A Solution B Solution C 25 g. sugar g. sugar distilled water
Hypotonic
Hypertonic
Isotonic
3. Determine which beaker contains a hypertonic solution, which contains a hypotonic solution, and which contains an isotonic solution.

9. I need to remember………
Osmosis is the movement of water molecules across a semi-permeable membrane.
Sometimes the movement of molecules across a semipermeable membrane requires energy.
When the number of molecules inside a cell is equal to the number of molecules on the outside of the cell, homeostasis has been reached—the cell is in equilibrium.

10. True or False
If fertilizer, containing a lot of salt ions, is placed on grass, water will move into the grass cells causing them to become turgid.
False

11. True or False
Water molecules can diffuse across the cell memebrane.
True

12. True or False
If a potato is soaking in a hypotonic solution, it will lose mass.
False

13. True or False
Salt ions can passively diffuse across the cell membrane.
False