Osmosis: Cell Wall and Sodium Chloride Solution

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Observing osmosis, plasmoylsis and turgor in plant cells
Investigation

* Get a single layer of plant cells. If you are using red onion, cut a 1 cm square from a fleshy piece of onion and then peel off a single layer of the red cells. If you are using rhubarb, peel a piece from the epidermis. If you are using toadflax peel a piece of the lower epidermis of a leaf. * Place the strip on a slide and cover it with a drop or two of distilled water. Add a cover slip. * Look at the cells through a microscope. Start with the low power lens. Draw and label 3 plant cells. * Take another strip of cells from your plant material. This time mount the cells on a slide with 5% sodium chloride solution. * Examine the cells through the microscope. Draw and label 3 plant cells. * After a few minutes draw out the sodium chloride solution with a piece of filter paper placed at the edge of the coverslip. Replace it with distilled water added at the other side of the coverslip.

QUESTIONS
1 Describe the cells in distilled water. How are the cells in 5% sodium chloride different from this? Describe what happens when you take away the sodium chloride solution and add water.

2 Explain what happened to the cells in sodium chloride solution using biological terms. Try to include these words.
cytoplasm
diffusion
water
solvent
dissolved salts
solute
cell membrane
vacuole
cell wall
osmosis
plasmolysis
turgid
flaccid
turgor
3 Explain what happened to the cells when you replaced the surrounding sodium chloride solution with water. Try to include the words from the list again.

4 What prevents the plant cells from bursting when they take in lots of water?

5 You’ve seen what happens to cells in epidermal tissue when they lose water. How does a whole plant look when it is short of water? How does it change when you give it water? Try to explain these observations using the ideas above.

6 Animal cells do not have the same...
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