1. Osmosis in Action
Mrs. Stewart
Biology

2. Table Talk Watch this video.
As a group discuss the answers to these questions:
What organism is this?
What kind of environment do you think it’s in?
What is happening?

3. Objectives
Predict the movement of water when a cell is placed in environments with varying solute concentrations
Recognize the importance of homeostasis as a survival mechanism

4. Quick Review Solutions have: Concentration: Osmosis: Solvent:
Solute(s):
Concentration:
Osmosis:
The liquid that dissolves the solute.
The substance that gets dissolved.
the amount of a substance in a given volume
When water moves from high to low concentration.

5. Cell Transport Passive Transport Active Transport Diffusion Osmosis
Facilitated Diffusion
Does NOT require energy, moves from HIGH concentrations to LOW concentrations
DOES require energy, moves from LOW concentrations to HIGH concentrations, moves LARGE molecules (glucose) via transport proteins
Moves small molecules, like CO2 & O2 gases, directly through the membrane
Movement of water across the membrane
Uses transport proteins to move large molecules through the membrane WITHOUT energy
3 Types of Solutions
Hypertonic
Isotonic
Hypotonic
Water moves out of the cell & it shrinks
Water moves into the cell & it swells
Water moves equally in and out of the cell; it stays the same size
Protein Pumps
Endocytosis
Exocytosis
Transport proteins that require energy to do work. Example: Sodium / Potassium Pumps are important in nerve responses.
Materials ENTER the cell through a vesicle formed by the membrane
Materials EXIT the cell through a vesicle formed by the Golgi Body
Controlled via the Cell Membrane

6. So What?
Cells live in solutions, both in the environment and in the body.
So we’ve named the three types of solutions:
Isotonic
Hypertonic
Hypotonic

7. Isotonic Isotonic: What happens:
Concentrations of solutes are the same inside and outside of the cell.
Water is at an equilibrium so it moves freely into and out of the cell at the same rate.
The cell stays the same – no change

8. Hypertonic Hypertonic What happens?
Concentrations of solutes are higher outside the cell than inside.
Water moves outside the cell in order to create a dynamic equilibrium.
Cells shrivel up and may die
(in plants this is called plasmolysis.)

9. Hypotonic Hypotonic: What happens:
Concentrations of solutes are lower outside the cell than inside.
Water moves into the cell in order to create a dynamic equilibrium.
Cells expand and may burst
(this is called cytolysis.)

10. Summary
Good graphic on page 99.

11. Review Watch this video again.
As a group discuss the answers to these questions:
What organism is this?
What kind of environment do you think it’s in?
What is happening?

12. Quick Review
Isotonic – solutes are __________ within the solution in comparison to the cell
Hypertonic – solutes are __________ within the solution in comparison to the cell
Hypotonic – solutes are ___________ within the solution in comparison to the cell
Equal
Higher
Lower

13. Objectives
Predict the movement of water when a cell is placed in environments with varying solute concentrations
Recognize the importance of homeostasis as a survival mechanism

14. Cell Responses to Osmosis
Land Organisms:
Saltwater Organisms:
Freshwater organisms:
Cells inside our bodies are in slightly hypotonic environments.
No problems under normal conditions.
Live in a hypotonic environment.

15. Hypotonic Environment Defenses
Single-cell organisms:
Contractile Vacuole:
Multi-celled organisms:
Solute Pumps:
a sac that stores water and when it is full the sac contracts and the water is expelled. (If it fails the paramecium will die.)
Proteins in the cell membrane can pump solutes out of the cell, making the concentrations of water more equal.

16. Plant Cells Hypotonic Environments: Turgor Pressure
Hypertonic Environments:
Plasmolysis
As the plant cell swells, the pressure of the water is not enough to break the cell wall. This gives soft plants rigidity.
(this is why plants stand tall)
As plant cells lose water, the cell membrane pulls away from the cell wall and turgor pressure is lost and the plant wilts.

17. No Defenses Some cells have no defense against osmosis. Example:
Red Blood Cells - hypotonic
Red Blood Cells - hypertonic

18. Review Watch this video again.
As a group discuss the answers to these questions:
What organism is this?
What kind of environment do you think it’s in?
What is happening?

19. Objectives
Predict the movement of water when a cell is placed in environments with varying solute concentrations
Recognize the importance of homeostasis as a survival mechanism