Cell Transport Lab

Cell Transport Lab

CELL TRANSPORT LAB – PLASMOLYSIS IN ONION CELLS

Purpose: The purpose of this activity is to investigate the effects of a hypertonic solution on the cells of the red onion.

Materials: Red onion epidermisSlideMicroscope

DropperDistilled waterPaper towels

5% NaCl solution

Procedure:

  1. Make a wet mount of the red onion epidermis using distilled water – but DO NOT use a cover slip.
  2. Examine the red onion epidermis under the microscope using low power. Once you have a clear image using low power, carefully switch the magnification to high power.
  3. Use a sheet of white computer paper to draw what you see. Use the Petri dish at your table to draw a circle for the field of view. Now, very neatly draw what you see of the onion specimen. Using colored pencils, shade the onion cells as they appear under the microscope. Label the cell wall and cell membrane. Make sure you include a title above the drawing and the total magnification below the drawing.
  4. Without moving the slide, carefully touch the edge of a paper towel against the slide to soak up the excess distilled water. Be careful not to push against the slide because this will cause the stage to descend.
  5. Carefully add approximately 2 drops of the 5% NaCl solution to the onion epidermis. Do not let the water run off the side of the slide – this will damage the microscope. Wait about 2 -3 minutes to give the NaCl solution time to diffuse into the cells.
  6. Observe the affects of the solution on the onion epidermis. You may need to use the fine adjustment knob to re-focus the image. If you cannot see the image using the fine adjustment knob, switch back to low power and re-focus.
  7. On your paper, make a second drawing of the onion specimen. Use colored pencils to shade the onion cells as they appear under the microscope. Label the cell wall and cell membrane. Make sure you include a title above the drawing and the total magnification below the drawing.
  8. Clean off the slide using a Kleenex, and return the slide to the Petri dish. Turn off the microscope, wrap the cord around the base, click the low power objective into place, and make sure the stage is all the way down.

Analysis: Answer these questions in complete sentences that re-state the question!!!

  1. Define hypertonic and hypotonic solutions. Which solution was hypertonic and which solution was hypotonic? (Out of the distilled water and the 5% NaCl solution)
  2. Describe in detail what happened to the onion cells when you added distilled water.
  3. Describe in detail what happened to the onion cells when you added the 5% NaCl solution.
  4. Why do grocery store owners spray fresh fruits and vegetables with water?
  5. Roads are sometimes salted to melt ice during a snow storm. What does this do to plants around the roadside and why?
  6. If a shipwrecked crew drinks sea water, they will probably die. Why?
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