Name: ______Period: ______

Examining Plant and Animal Cells

Purpose: To examine the basic structure of plant and animal cells.

Materials:

  • Glass slides
  • Cover slips
  • Toothpick
  • Microscopes
  • Paper towel pieces
  • Methylene Blue stain
  • Iodine stain
  • Paper towels
  • Petri dishes

ONION CELL

PROCEDURE:

  1. Remove a thin piece of onion epidermal tissue from the inner surface of the onion.
  2. Place one drop of water on a slide and place the onion flat in the water.
  3. Cover with a cover slip.
  4. Use the SCANNING (4x) objective to focus. Observe in this power but do not draw.
  5. Take the slide off the microscope and place a drop of iodine stain near the edge of one side of the cover slip. As instructed by your teacher, draw the stain through the sample using a piece of paper towel. (Caution: Iodine will stain clothes and skin!)
  6. Switch to low power (10x). Cells should be visible. They will be small and look likeyellow bricks. (Remember-DO NOT use the coarse adjustment knob at this point!!!)
  7. Switch to high power (40x) and refocus. (Remember-DO NOT use the coarse adjustment knob at this point!!!
  8. Sketchthe cell at low (10x) and high power (40x). LABEL the organelles that you can identify (cell wall, vacuole, etc.). Draw your cells to scale! Record the total magnification below your drawing.

RESULTS:

Power: ______Power: ______

Total Magnification: ______Total Magnification: ______

HUMAN CHEEK CELL

PROCEDURE:

  1. Put a drop of methylene bluestain on a slide. (Caution: Methylene Blue will stain clothes and skin!)
  2. Gently scrape the inside of your cheek with the flat side of a toothpick. Scrape lightly.
  3. Stir the end of the toothpick into the stain and throw the toothpick away.
  4. Place a coverslip onto the slide.
  5. Use the SCANNING (4x) objective to focus. You probably will not see the cells at this power.
  6. Switch to low power (10x). Cells should be visible, but they will be small and look like nearly clear purplish blobs. If you are looking at something dark purple, it is probably not a cell. (Remember-DO NOT use the coarse adjustment knob at this point!!!)
  7. Once you think you have located a cell, switch to high power (40x) and refocus. (Remember-DO NOT use the coarse adjustment knob at this point!!!)
  8. Sketchthe cell at low (10x) and high power (40x). Label thenucleus,cytoplasm, andcell membrane. If you have a good sample you may see the nucleolus. Draw your cells to scale! Record the total magnification below each your drawings.

RESULTS:

Power: ______Power: ______

Total Magnification: ______Total Magnification: ______

QUESTIONS:

  1. What is the general shape of the onion cells? The cheek cells?
  2. Based on your drawings, which type of cell is larger, plant or animal? Explain your answer.
  3. Why is methylene blue and iodine necessary for this lab?
  4. When staining the cells, which part of the cell stains darker than the other parts?
  5. What differences can you see between the animal and plant cells? What structures do they have in common? Give at least 2 for each.
  6. Keeping in mind that the mouth is the first site of chemical digestion in a human. Your saliva starts the process of breaking down the food you eat. Keeping this in mind, what organelle do you think would be numerous inside the cells of your mouth?