1. Osmosis & Tonicity
This is going to show how cells transport substances in and out. 1

2. Osmosis through an Egg Membrane
Check your results!

3. Diffusion across a membrane Semipermeable membrane
The Plasma Membrane
12/4/2018
Osmosis
Diffusion of water across a membrane
Moves from HIGH water potential (low solute) to LOW water potential (high solute)
Diffusion across a membrane
Semipermeable membrane 3
G. Podgorski, Biol. 1010 3

4. Let’s take a closer look!

5. If the Solute can move through the membrane, it will diffuse until it reaches Equilibrium
BUT WHAT IF the solute could not pass through the membrane?
Can both sides reach equilibrium?

6. If the solute (purple) cannot get past the membrane, can the 2 sides of the tube reach equilibrium?
What do you think will happen?

7. The solute cannot move, but the WATER can!!

8. Salt SUCKS! Sugar SUCKS! Solutes SUCK!
Solutes will “suck” water to balance out the solute concentration
Not Equal Equal concentration

9. We label solutions as hypertonic, hypotonic, or isotonic to help us understand the location of the highest solute concentration.

10. Hypotonic—Lower concentration of solute in solution (Sugar, Salt, etc
Isotonic—Same concentration of solute in solution
Hypertonic—Higher concentration of solute in solution

11. Hypotonic Solution “Hypo” = below or less
Higher solute concentration inside the cell
Water will move into the cell
Cell will swell and burst (lyse)
If the solution is HYPOtonic,
then inside the cell is
HYPERtonic

12. Hippo – Hypo: both are enlarged
Hypotonic solution
Hippopotamus
Red Blood Cell in
Hypotonic Solution
Hippo – Hypo: both are enlarged

13. Isotonic Solution “Iso” = same
Solute concentration is the same on both sides of the membrane
Water will show no net movement
Cell will show no change in size

14. Isotonic Solution Helpful Visual
Red blood cell in
Isotonic Solution
isosceles triangle
Both refer to something that is the same

15. Hypertonic Solution “Hyper” = more or greater than
Solute concentration is higher OUTSIDE the cell
Water will move OUT of the cell
Cell will shrivel and die
If the solution is HYPERtonic,
then inside the cell is
HYPOtonic

17. NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
The Plasma Membrane
12/4/2018
Isotonic Solution
Hypotonic Solution
Hypertonic Solution
NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
CYTOLYSIS
PLASMOLYSIS 17
G. Podgorski, Biol. 1010 17

18. Cytolysis & Plasmolysis
The Plasma Membrane
12/4/2018
Cytolysis & Plasmolysis
Cytolysis
Plasmolysis
G. Podgorski, Biol. 1010 18

19. What would happen to the animal cells in each beaker?
100% Distilled Water
80% H2O
70% Water 30% Dissolved Substances
80% H2O
80% Water 20% Dissolved Substances
80% H2O
Ask the students to predict what would happen to the cells in the beaker. You may want to explain solutions first. Dissolved substances would be sugars, salts, ions, etc.

20. Which way did the water move?
100% Distilled Water
80% H2O
Have the students predict – and then show the answer. You have to click to get the beaker and the question to show.
Why did the cell get so big?

21. Which way did the water move?
80% Water 20% Dissolved Substances
80% H2O
Predict and show answer.
Why did the cell stay the same size?

22. Which way did the water move?
70% Water 30% Dissolved Substances
80% H2O
Predict and show answer.
Why did the cell get so small?