Cell Observations:
Typical Plant, Animal, and Bacteria Cells
Data: Draw Onion Cell and Cheek Cell Drawing in notebook, low,
medium, and high power. View three shapes of bacteria and draw one
example, choose power.
In a previous laboratory experience you learned how to use the
microscope and make wet mounts. In this lab activity you will prepare
two different wet mounts and observe some plant and animal cell
slides.
PART ONE:
Onion Cell Wet Mount
1. Peel a translucent piece of tissue from the onion (the smaller the
piece the better). Translucent means that you can see light through
the specimen, but it is not transparent.
2. Place the piece of onion on a glass slide and add a drop or two of
the Lugol's solution. (Lugol's solution or iodine is a specific stain
for plants.) Cover the slide with a cover slip using your best wetmount slide technique.
3. Observe the onion cell under all powers. Make a drawing of one
onion cell, using a pencil, labeling all of its parts as you observe
them.
(At minimum you should observe the nucleus, cell wall, and
cytoplasm.) Note, plant cells usually contain chloroplasts, but you
won’t find any in the onion piece.
Figure 1: Onion Cell 40x, Figure 2:
3: Onion Cell 400x
Onion Cell 100x, Optional Figure
Choose the best field of view to locate a few of the organelles and
label them on one of your drawings (at minimum you should observe the
cell wall, cell membrane, nucleus, and cytoplasm). You might also be
able to see some chloroplasts, but only if your onion tissue is
somewhat green.
PART TWO:
Cheek Cell Wet Mount
1. To view cheek cells, gently scrape the inside lining of your cheek
with a toothpick. DO NOT GOUGE THE INSIDE OF YOUR CHEEK! (We will
observe blood cells in a future lab in 8th grade!! )
2. Gently tap the toothpick onto the center of a glass slide.
of the cheek cells should fall onto the slide.
Some
3. Add a drop of methylene blue stain (specific for animals) and
cover with a cover slip.
4. Observe the cheek cells. Data:
low, medium, and high power
Cheek Cell Drawing in notebook,
Figure 1: Cheek Cell 40x, Figure 2:
3: Cheek Cell 400x
Cheek Cell 100x, Optional Figure
Choose the best field of view to locate a few of the organelles and
label them on one of your drawings (at minimum you should observe the
cell membrane, nucleus, and cytoplasm.)
PART THREE: Bacteria Cell Observation
1. Bacteria Cells are not easy to view under a compound microscope
unless we use already prepared slides. Select a slide from the
counter.
2. For each of the three shapes, cocci, bacilli, and spirilla draw
one drawing in which you choose the power.
Figure 1: Cocci Cells - choose power, Figure 2: Bacilli Cells choose power,
Figure 3: Spirilla Cells - choose power
Analysis Questions
a.
Why do we stain specimens?
b.
Why must the specimen you observe be very thin?
c.
What is the general shape of a typical plant cell? …of a typical animal
cell?
d.
Inside the mouth, these cells are joined together in a sheet. Why are
they scattered on
your slide?
e.
Do you think all living creatures have the same size and shape of cells?
Why or why not?
I.
Copy the following chart in your notebook and fill in the
columns
Cell organelle
of the
Are these structures found in
plant
cells, animal, bacteria or
Structure?
all three?
nucleus
What is the function
Organelle or
cell wall
chloroplast
cell membrane
cytoplasm