Download using the compound microscope to study animal and plant cells

USING THE COMPOUND MICROSCOPE TO STUDY
ANIMAL AND PLANT CELLS
Materials
Banana fruit
Iodine solution
Procedure
1. Place one or two drops of an iodine solution on a slide. Get a small amount of
the pulp of a banana fruit on the tip of a toothpick and place it in the iodine.
Separate the banana pulp by mixing it in the iodine solution with the toothpick.
Add a cover slip and press it gently so that you have a thin mount. If you need
more liquid to fill the area under the cover slip, add a drop of iodine at the
edge of the cover slip. The liquid will flow under the slip.
2. Place the slide on the stage of the microscope and use the 10X objective to
focus on the cells of the banana. Most of the cells of the pulp of the banana
are living parenchyma cells. Parenchyma cells carry on many chemical
reactions necessary for the life of a plant. In fleshy fruits such as the
banana, many of the parenchyma cells store food, and the most obvious
structures you see in the cells are starch grains that stain light lavender to
dark purple with the iodine. Turn to the 40X objective and observe the
layered appearance of the starch grains.
4.
Diagram the parenchyma cells from the fruit of a banana. Label the cell wall,
cytoplasm, starch grains, and vacuole.
Materials
Epithelial cells from the inner cheek
Methylene blue (a dye)
Procedure
1. Place a drop of methylene blue solution on a clean slide. Run the end of a toothpick
carefully over the inside of your cheek and place the material in the dye on the
slide, mixing it up a little. Gently add a cover slip and examine the slide with the
microscope, starting with the 10X objective and then changing to the 40X
objective. Focus up and down carefully with the fine adjustment. You are looking
at epithelial cells that line the inner cheek. Animal cells, unlike plant cells, do not
have a cell wall. The outer surface of the cell is the plasma membrane. Notice as
you focus up and down that these cells are more squashed than were the
parenchyma cells of the banana, even though you did not apply pressure on the
cover slip. This is because they lack a rigid cell wall. Animal cells also lack a large
central vacuole.
2. Diagram an epithelial cell from the cheek and label the plasma membrane, cytoplasm,
nucleus, and nucleolus.
Materials
Leaf of Elodea
10% salt solution
Procedure
1. Place a drop or two of water from the container onto a slide and select a bright
green, young leaf of Elodea and place it in the water on the slide. Place a cover slip
over the leaf. If additional water is needed to fill the area below the cover slip,
add some water at the edge of the cover slip. If there is too much water, remove
some by holding a piece of paper towel at the edge of the cover slip.
2. Draw a picture of what you see under low power and high power.
3. In parenchyma cells, the plasma membrane usually is pressed against the cell wall
and is difficult to see. Replace the water around the Elodea leaf under the cover
slip with a 10% salt solution. (Do not get salt water on the microscope.) A
concentration gradient will cause the water to leave the cells through osmosis. As
water leaves the cells, the volume of the vacuole is decreased and the cytoplasm
shrinks away from the cell wall. You will then be able to see the plasma membrane.
4. Observe and record any changes.
5. Describe the shape of the chloroplast.