1. Cell Function and Diffusion

2. How to follow Lab Instructions… thoroughly!
Example:
Instructions for how to clean up after your dog!
By Contributor - Own work, CC BY-SA 3.0,
To pick up after your dog, use your hand
To pick up after your dog, use your hand that you covered with a plastic bag (turned inside-out).

3. How to follow Lab Instructions…
Read entire list of Instructions.
Gather materials.
Label them.
Follow Procedure step by step.
Check off each completed step.
Record data
Analyze and conclude.
Clean-Up!

4. Diffusion
Movement of molecules from a higher to a lower concentration until equilibrium is achieved
Dependent on temperature, size of molecules, and type of medium (solid, semi-solid, liquid, air)
By JrPol - Own work, CC BY 3.0,

5. Types of Diffusion Air Liquid Semi-solid
Semi-permeable membrane (Osmosis)
Dialysis tubing
Copyrighted free use,
By Mike aus dem Bayerwald - Own work, CC BY-SA 3.0,
By M.Mack - HS-Mannheim, Institut für technische Mikrobiologie, CC BY-SA 3.0,

6. Diffusion
Diffusion of methylene blue in agar (semi-solid) versus water (liquid)
In which medium did the dye diffuse the fastest?
© Kornelia Fillmer, CC BY-SA 3.0

7. Osmosis – Diffusion of Water across semi-permeable membrane
1. Where is the concentration of the solutes higher?
= Hypertonic
= Hypotonic
= Hypertonic
Semi-permeable
membrane
The other side must be Hypotonic

8. Hypertonic, Hypotonic, Isotonic -Tonicity, it’s all relative -
Ted
By pixabay.com, CC0 Public Domain,
Jim
Bill
Is Jim tall?

9. Water moves. Always from “o” to “er”
If solute molecules are too large and can’t move through membrane, then…
Water moves. Always from “o” to “er”
Water moves from Hypotonic to Hypertonic
H2O
Hypotonic
Hypertonic

10. So same concentration on both sides
In the end: Isotonic!
So same concentration on both sides
Number of solute molecules on either side do not change (they did not move!)
H2O moved, making left side smaller (shrink) and right side bigger (expand, turgid or even burst)
Isotonic
Isotonic

11. Where is the concentration of solute higher? => Hypertonic
=> other side = Hypotonic
Water moves from Hypotonic to Hypertonic
From ‘o’ to ‘er’
What will happen?
Hemolysis in animal cells (burst); Turgid in Plant cells
H2O
Hypertonic
Hypotonic

12. Where is the concentration of solute higher? => Hypertonic
=> other side = Hypotonic
Water moves from Hypotonic to Hypertonic
From ‘o’ to ‘er’
What will happen?
Hemolysis in animal cells (burst); Turgid in Plant cells
0.5% NaCl
0.9%
NaCl
H2O
Hypertonic
Hypotonic

13. Where is the concentration of solute higher? => Hypertonic
=> other side = Hypotonic
Water moves from Hypotonic to Hypertonic
From ‘o’ to ‘er’
What will happen?
Crenation in animal cells (shrivel); Plasmolysis in Plant cells
1.5% NaCl
0.9%
NaCl
H2O
Hypertonic
Hypotonic

14. Tonicity Isotonic Hypertonic Hypotonic
Relative concentration of solute (particles) or solvent (water) outside the cell compared to inside
3 Types
Isotonic
Hypertonic
Hypotonic

15. Tonicity and red blood cells
Check out tubes of prepared red blood cell (RBC) solutions
RBCs are floating either in Hypertonic, Isotonic, or Hypotonic solution
By Osmotic pressure on blood cells diagram.svg: LadyofHatsderivative work: Antoni Salvà (talk)This vector image was created with Inkscape. - Osmotic pressure on blood cells diagram.svg, GFDL,

16. Tonicity and red blood cells
By Zephyris - Own work, CC BY-SA 3.0,

17. Tonicity and Elodea Cells
Hypotonic
Tap water
Turgid – Turgor Pressure
Hypertonic
In 10% NaCl solution
Water has left the cell across the plasma membrane
Notice how cell membrane has shrunk away from cell wall and chloroplasts are all clustered in middle
Plasmolysis
By Cimice50 (Own work) [CC BY-SA 4.0 ( via Wikimedia Commons
© Kornelia Fillmer, CC BY-SA 3.0

18. Tonicity Plant Cells
By LadyofHats - did it myself based on [1], [2] ,[3] and [4]., Public Domain,

19. Testing for the presence of Starch and Glucose
© Kornelia Fillmer, CC BY-SA 3.0
Adding Iodine to water turns the color slightly amber (looks like tea) In the presence of Starch, the color turns dark
Adding the blue Benedict’s reagent to a sample turns the color to blue. Heating the sample for 5 minutes will turn the sample orange if glucose is present.
© Kornelia Fillmer, CC BY-SA 3.0
© Kornelia Fillmer, CC BY-SA
© Kornelia Fillmer, CC BY-SA

20. Next Lab Read Exercise 5 in Lab Manual Post Lab Quiz 4 now open
Deadline: Day before next Lab at 9:00pm
© Kornelia Fillmer, CC BY-SA 3.0

21. Changes to the 1e Lab Manual
Page “Which solute did not diffuse across the dialysis membrane from the beaker?” Change the word “from the beaker” to “out of the tube”
Page 38 add this questions: “10. If you would have tested the beaker liquid after waiting the 5 minutes in step 6 with Benedict’s reagent, heating the testing solution would have turned its color from blue to orange. Why?”

22. Activities Station A Station D* Station B Station C
A: “To Do” page 36 Diffusion Semisolid “To Do” page 36 Diffusion Liquid (60 sec)
B: “DEMO” page 37 – 38 Dialysis bags
C: “To Do” page 40 Red Blood Cells
D: “To Do” page 42 Plant Cell Tonicity*
* Group “D” starts the potato strip for the entire class and records start time. Other groups skip this station until the 1 h wait time is over to record results.
Station A
Station D*
Station B
Station C