Part II Structure of Living Cells

Materials: Microscope, dropping bottle, onion, slides, iodine,

potato, cover slips, forceps, toothpick.

ProcedureA:

  1. Obtain an onion scale and remove a paper thin layer of tissue from the surface. Place the tissue in a drop of water on a slide. Take care to spread it flat without tearing or wrinkling. Add a cover slip, being careful to avoid air bubbles. Observe slide under low power.
  1. What is the shape of the cells?

______

  1. What cell structures can you identify?

______

  1. With the cells under observation on low power, add a drop of iodine stain to the edge of the cover slip. Handle carefully: stains can permanently damage clothing. Describe the change in the cells after adding iodine.
  1. Center several cells in the field of view. Switch to high power and observe the cells carefully. Remember that as magnification increases, the field of vision decreases. Draw several onion cells in the space below. Label the cell wall, cytoplasm, nucleus, nucleoli.

Procedure B:

  1. Shave off a thin piece of potato. Prepare a wet mount by placing the potato sample in a drop of water, adding a drop of iodine, and placing a cover slip over the sample. Examine the slide under low power.
  2. How do the cells differ from the onion cells?
  1. The black areas are starch grains being stored in cell organelles called leucoplasts. Why does a potato plant store starch in these cells?
  1. In the space below, sketch several potato cells as viewed under low power. Label the cell walland leucoplast.
  1. Animal cells:

With the toothpick, scrape some cells from the inner lining of your cheek. Put these cells in a drop of water and a drop of iodine on the slide. Examine under low power.

  1. What is the difference between those cells and the plant cells?
  1. In the space below, sketch some cheek cells. Label the cell membrane, nucleus, and

cytoplasm.

  1. Take oneElodea sample. Prepare a wet mount slide with a drop of water and observe under low power.
  1. Can you see a cell wall? ______
  2. What do you think the green structures are? ______
  3. What is the jelly-like fluid between the green structures? ______
  4. Is this a plant or animal cell? ______
  5. What two structures does a plant cell have that animal cells do not have?______
  6. Why does Elodea have chloroplast? ______

Switch to high power. Try to locate moving chloroplast. What cell structure is responsible for this movement? ______

Sketch several Elodea cells. Label the cell wall, cell membrane, nucleus, chloroplast, and cytoplasm.