1. How did we use indicators in the Diffusion Lab?
Warm up
How did we use indicators in the Diffusion Lab?
SWBAT explain diffusion and osmosis by answering analysis questions in their lab packets
Standard:
1.2g Each cell is covered by a membrane that performs a number of important functions for the cell. These include: separation from its outside environment, controlling which molecules enter and leave the cell, and recognition of chemical signals. The processes of diffusion and active transport are important in the movement of materials in and out of cells. 1.2h Many organic and inorganic substances dissolved in cells allow necessary chemical reactions to take place in order to maintain life. Large organic food molecules such as proteins and starches must initially be broken down (digested to amino acids and simple sugars respectively), in order to enter cells. Once nutrients enter a cell, the cell will use them as building blocks in the synthesis of compounds necessary for life.
WARM UP discussion:
Find your Diffusion Lab

2. Diffusion Through a Membrane
DIN – Turn your lab over to the back. Write down a few sentences about what is happening in the video AND why it is happening.
EGG VIDEO

3. Review of the Cell Membrane
The Cell Membrane is Semi-Permeable or Selectively Permeable
Small molecules (like glucose) are able to pass through the membrane while large molecules (like starch) cannot pass through

4. Diffusion Through A Membrane
glucose molecule
PART of a starch
molecule

5. What we used for the lab
Dialysis Tubing – used to make a “cell” that will allow small particles to pass through and not large particles
Glucose Solution – a simple sugar made of one small molecule of sugar
Starch Solution – a complex carbohydrate made of hundreds of simple sugars bonded together

6. Indicators
Starch Indicator Solution – (Iodine), a really small molecule (It’s only 2 atoms big)
Glucose Indicator Solution – Benedict’s solution

7. Initial Cell “Cell” with glucose and starch
Water and starch indicator solution

8. The Final Cell The water stayed amber The cell turned blue-black
Water from outside the cell tested positive for glucose

9. Quick Video of Iodine (Starch Indicator Solution) diffusing INTO the Cell!

10. What Happened??
Glucose was small enough to pass through the membrane so it ended up in the water outside the cell
Starch was too big to pass through the membrane so it didn’t get out of the cell
Iodine (starch indicator solution) was small enough to pass through the membrane so it ended up in the cell turning the cell blue-black

11. Diffusion Through a Membrane

13. Diffusion Through a Membrane

14. RED ONION IN FRESH WATER

15. Red Onion in Fresh Water
cytoplasm
red onion cells
in tap water
cell membrane
cell wall

16. Add Salt Water to Cells bathing the cells in NaCl = salt
water, by “wicking”
it through
NaCl

17. RED ONION IN SALT WATER

18. Diffusion Through a Membrane
cytoplasm
red onion cells in
salt water
cell membrane
cell wall

19. Diffusion Through A Membrane
bathing the cells in
distilled water,
by “wicking” it
through

20. Diffusion Through a Membrane
cytoplasm
red onion cells
in distilled water –
returned to normal
cell membrane
cell wall

21. Diffusion Through A Membrane
Which cell is in distilled water and
which is in salt water?

22. Diffusion Through A Membrane
Applications –
salt on roads to melt snow
intravenous saline solutions
salty foods make you thirsty
salt on slugs to kill them
salty foods do not spoil as easily
gargling with salt water
digestion of starch to glucose

23. Quick video of what happened to iodine in “cell” tube
A diffusion lab for absent students
Student summary of diffusion state lab
Osmosis demo with raw egg

24. Activity – Analysis Questions
Your table will be assigned one question from the analysis section on pages 8 and 9
Work on the question with your table for 5 minutes and put your answer on your easel.
Be ready to share and explain to your classmates
** If you finish early, check that ALL other sections of the lab are complete

25. REGENTS PRACTICE Reflection Answer on looseleaf and attach to lab
How did we observe diffusion and osmosis in this lab activity? Did this help with your understanding of these concepts? Explain.
Why was lab safety important during this activity?
What was your favorite part of this lab? What was most challenging?

27. Ticket out the Door Think of our experiment yesterday…
What molecule diffused OUT of the “cell”? Why was it able to?
What molecule could NOT diffuse out of the “cell”? Why not?
What molecule diffused INTO the cell? What did it react with in the cell? How could you tell it reacted?