Variations in Cell Structure
Objectives
 To examine several different kinds of cells
 To observe similarities and differences between the cells
Background information
All cells are basically similar in having cytoplasm bordered by a plasma membrane, they vary
considerably in structure, depending on the specific function they serve the organism in which they
are formed. Since plants lead a stationary existence, it’s appropriate that their cells should have
rather rigid cell walls for support. Animals, on the other hand, have to move around and need more
flexible cells.
To be handed in
Lab report, which includes:
 All of the answers to the questions asked in the lab, with the proper headings. The answers
that you hand in should be answered in complete sentences and TYPED.
o A powerpoint for your group with the following on each slide.
o Magnification must be labeled for each picture! Example 40 x, 100x, or 400x
o All visible organelles (and those specified to be labeled) should be labeled
o Finished powerpoints must be submitted to my drop box on the server.
1. Elodea
a. Remove a fresh green leaf from an Elodea plant and hold it gently between your
fingers for a few minutes to warm it.
b. Prepare a wet mount of the whole leaf, use a cover slip.
c. Examine the entire leaf under the scanning power objective until you find a section
where cells are clearly visible. You are looking for 1 cell thick.
d. Center these cells in the field and then focus under low (yellow) to high power
(400X).
e. Carefully and slowly shift the focus with the FINE adjustment to study the cells at
various depths.
f. Take a picture on high power and label the cell wall, the cell membrane, the nucleus,
chloroplasts, and vacuoles. Color the chloroplasts green. Are the chloroplasts
moving? If so, indicate direction on your drawing.
g. Answer questions.
2. Potato
a. Carefully cut a piece of potato, and use a razor blade to carefully shave off a thin
piece of tissue from the flat end.
b. Prepare a wet mount of this section, using a cover slip.
c. Observe it under scanning power, and answer questions
d. Remove the slide from the stage of the microscope and add one drop of iodine to the
edge of the cover slip. Place it immediately back under scanning power to observe.
e. Focus the potato under low power, then switch to medium, and if possible, to high
power.
f. Take a picture of your slide what you see and label the cell wall, cytoplasm, and
starch grains.
g. Answer questions.
3. Onion
a.
b.
c.
4.
5.
6.
7.
skin
Take an onion and peel away one of its layers.
If you snap the layer in half the correct way, a thin, clear piece should be intact.
Take 2 pictures. One with no iodine and 1 with iodine on it. Both on high power
after focusing.
d. Label the cell wall, nucleus, cytoplasm.
e. Answer questions.
Tomato skin
a. Remove a small section of tomato skin and trim to about a 1/2 inch square
b. Scrape off any pulp left on the lower surface of the skin
c. Keeping the lower surface of this skin down against the slide, prepare a wet mount
and add a cover slip
d. Examine under low and high power.
e. Take a picture and label on high power, labeling the cell wall, nucleus, cytoplasm, and
chromoplasts.
f. Answer questions.
Tomato Pulp
a. Smear a small amount of fresh tomato pulp on a slide
b. Add one drop of water and a cover slip
c. Adjust the diaphragm to reduce the light intensity and observe under low power.
d. Take a picture, labeling the organelles that you see.
e. Answer the questions.
Beet pulp
a. Cut a piece of beet about 1 inch wide and 1 inch long. Using a razor blade, shave off a
thin piece of tissue. This needs to be REALLY REALLY thin for you to see what you
need to see!
b. Prepare a wet mount of the specimen, and observe under low power.
c. Carefully switch to high power and observe again. Take a picture. Label parts
d. Answer questions.
Human cheek cells
a. Place one drop of water in the center of a clean glass slide.
b. Gently scrape the inside of your cheek with a toothpick.
c. With a swirling motion, smear the material collected into the water on the slide.
d. Add one drop of iodine stain and a cover slip.
e. Examine under low power and search for an arc of individual cells.
f. Examine under high power.
g. Take a picture and label organelles that you see
h. Answer the questions.
Questions to Answer
(to be typed in complete sentences separately)
1. Anacharis (Elodea)
a. The oval green bodies in the cytoplasm are chloroplasts. Do they appear to be
moving? Are they moving?
b. If they are moving, is it in the same direction in an individual cell? Is the direction
the same in all the cells you can see? Are the chloroplasts all moving at the same
rate of speed? (If you do NOT see them moving, then make a hypothesis!)
c. Do the chloroplasts have any structures for locomotion? You may have to look this
one up in a book…account for their movement! (Even if you see them not move, look
this up in a book or on the internet!)
2. Potato
a. Describe the cells that you observe.
b. Do you find any chloroplasts in the cells?
c. What color is the iodine as it is leaving the bottle? What color does it stain potato
cells?
d. Iodine turns blue-black in the presence of starch. Is there starch in potato cells? If
so, where is it located? (Everywhere, organelles)
e. If you did not see chloroplast, could you hypothesize why not? (hint…where do
potatoes grow?)
3. Onion skin
a. Do these two plant cells react the same way to iodine?
b. Does your hypothesis from above (potato part e) agree with your findings? Explain.
4. Tomato Skin
a. Is the tomato skin more than one cell thick?
b. Are the cells the same size and shape? Describe their shape.
c. What color pigments do you see in the cell?
d. We know that chloroplasts are green because they contain chlorophyll. These are
red, meaning no chlorophyll. In tomatoe, what are the plastids called?
e. Describe the structure of the cell wall.
5. Tomato Pulp
a. What is the color of the cell?
b. What is the shape of the cell?
c. How does the cell wall compare with the tomato skin cell wall?
d. Account for the differences in the two types of cell walls. You may need to reread
the cell wall info from the text.
e. What is the arrangement of the chromoplasts in the cells? Is it different than the
tomato skin arrangement?
f. Account for the intensity of the red color in the whole tomato.
6. Beet pulp
a. Describe the cell wall.
b. Are there pigments present? What color are the pigments?
c. Are the pigments localized in the plastids or are they dispersed throughout the
cytoplasm?
d. Could this be the same pigment found in the tomato? If it is, describe the
differences that you observed.
7. Human Cheek Cells
a. Do the cells possess a wall? If not, what do they possess?
b. Study the cells under high power. Do they have the same shape? Are they all the
same? (be careful of folded cells!)
c. Do the cells possess a vacuole? A nucleus? Chloroplasts?
1.
2.
3.
4.
Conclusions
List at least 4 similarities between plant and animal cells.
List the main structural differences observed between plant and animal cells.
List three ways that cells taken from a specific area or structure in an organism are similar.
What is the purpose of staining the cells that you have observed in this activity.