Sec: Name: . ._Experiment: Osmosis in Uving Cells

(8. Science 10-7-3e)

Purpose: To demonstrate turgor pressure in planttissues, observe cells in various salt

.concentrations, and determine if osmosis occursin living cells.

Materials: potato slices cucumber slices3 - 250 ml beaker distilled water 15% NaGI

.onion microscope glass slidescover glass dropper paper towel

Methods: Part A: Turgidity in Plant Tissues1. Place 50 mL of distilled water in one beakerand with the second add 50 mL of 15 % NaGI~olution. Obtain 3 slices of potato and 3 slices of~ucumber. Place one of the slices of potato in onJeaker with distilled water and another slice in the)eaker with 15 % NaC/. Place a third potato slicem the desk. Place the cucumber slices the same.vay. Leave the dishes for about 1/2 an hour.

z. ·ooseNe the fresh vegetables that had not been placed in any of the dishes. Howwould you describe their stiffness and texture?3. Hemove some of the vegetables from the distilled water. How would you describetheir stiffness and texture?

4. Has the turgidity of the cells in the distilled water increased or decreased?5. \/Vhat conclusions can you draw from this observation?6. Hemove some of the slices from 15 % salt solution. How would you describe theirstiffness and texture?7. Do these slices have greater or lesser turgidity than the slices that were not in anyof the dishes?

8. Explain why the turgidity is the way it is with slices in the NaGI solution.

Part B: Osmosis in Plant Cells1. Cut a small piece of onion, remove the epidermis layer that is 1 cell thick. Prepar\1 8wet mount (with tap water) of this & observe on high power. Draw observations.2. Describe the position of the cell membrane and' the cell wall.3. Place one drop of 15% NaGI solution at the edge of the cover glass. About every30 seconds. add another drop of NaGI solution until you observe a change inappE~aranceof the cell. How many drops of NaCI were added before a change wasnoticed?

4. Do you think that water moved in or out of the cell?5. VI/hy do you think this change occurred?6. Draw the cell that you observed after NaGI was added.7. Place a piece of paper towel at the edge of the cover glass and absorb as much ofthe salt solution as possible. Add distilled water at the edge of the cover glass, a dropat a time, watching the cells closely. Do you observe any changes in the cells?8. Draw the cell that you observed after the distilled water was added.

Sec.: Name: _Results: Part A: Turgor in Plant Tissues2. fresh vegetable$: _3. vegetables in water:4. turgidity: 5. conclusions:6. vegetable In salt:7. turgidity: 8. Explain: _Part B: Osmosis in Plant Cells

x x x

Step 1 (tap water) Step 6 (salt) Step 8 (distilled)2. Cell membrane and wall: _3. Drops of NaCI: 4. Direction:5. Why: _7. Changes:

Conclusions:1. Did osmosis oCCurin part A of the experiment?2. Did diffusion take place when NaCI solution was added to the onion csl/s?Explain result3. How would you explain the condition of the vegetable slices that were In the saltsolution?

4. How would you explain the condition of the vegetable slices that were In thedistilled water?

Discussion:1. How would you define turgidity?

2. Of what value Is turgidity to a plant?

3. How come animal cells can't have the same amount of turgidity as plant cells?

4. What purpose did the freshly cut vegetables (not placed In any beakers) serve inthis experiment?

5a. Read Matthew 21:19 -22. Because there was no fruit what did Jesus do to the tree?

5b. We are not sure of the mechanism of how he did this to the tree. If He chose touse osmotic pressure to do this, would he cause the soil around the root to be isotonic,hypotonic, or hypertonic to cause the cells, therefore the tree, to do what It did?

5c. What Is the promise Jesus leaves us with (vs. 22)?