Download Lab: Investigating Cell Variety Part 1

General Biology
Lab:
Investigating Cell Variety
Part 1
Class Copy
Objective:
1. Observe and draw diagrams of the different kinds of cells.
2. Identify and label cell parts in diagrams of protest, animal and plant cells..
3. List each cell part’s function.
4. Describe characteristics that distinguish protists cells from animal and plant cells.
Materials:
Read the lab and write down all the materials you will need.
Prelab Questions Introduction and Part 1:
Read the Introduction and Procedure for Part 1 and answer the following questions:
1. What does the Cell Theory say about the say?
2. Which objective lens is low power?
3. Medium power?
4. High power?
5. What does cytoplasm look like?
6. What magnification do you use to draw your Amoeba cells?
7. How many cells will you draw?
8. How many times do you label each cell part?
9. What parts will you be labeling in the Amoeba?
10. Are you collecting qualitative or quantitative data?
11. What is the function of a nucleus?
12. What kind of cell is an amoeba?
Introduction:
Part of the Cell Theory states that the cell is the basic structural, functional, and developmental unit of life. If
this theory is correct, then all living things should be made up of cells. It should also be true that the cells of
different organisms should have some basic similarities and at the same time, we should expect certain basic
differences because of the differences in cell function and type.
In this lab, you are to use the light microscope to examine the cellular make up of different organisms- protists,
animals and plants, animal and protist. You are to look for and record the obvious similarities and differences
between the cells, and make diagrams of each observation. You will examine the cellular parts found in
certain kinds of cells that can be seen by with the light microscope.
Part 1: Amoeba cells (Protist Cell-prepared slide)
In your tray you will find a prepared slide. It is marked “Amoeba Proteus.” Report any damage to this slide to
your teacher before you begin.
1
General Biology
An Amoeba is a relatively large single-celled organism known as a protist that lives in ponds and lakes. It has a
very irregular shape. The Amoebas on this slide are stained various colors. The stain causes many of the cell
structures to be more visible.



Scan this slide on low power until you find and focus in on a single amoeba cell.
Switch to medium power and find and focus in on the stained Amoebas. Disregard other smaller stained
cells and debris.
You should be able to find and identify the following structures:
Cell Membrane: The outer most layer of the cell. The cell membrane controls the movements of molecules
into and out of the cell.
Cytoplasm: This is the clear space between the nucleus and the cell membrane.
Nucleus: The control center for the cell. It contains chromosomes, in which genes are located. The nucleus
controls all activities of the cell. It will be seen as a dark spot on the inside of the cell.


Finally, switch to high power. Examine at least 3 different typical Amoeba cells. Draw and label two such
cells. Follow lab drawing rules. In one cell, label all the parts you observed. Attach these lab drawings in
your lab notebook. When you are done, let your teacher know you are ready to be considered for a
completion stamp.
You should be able to find and label the following: cell membrane, cytoplasm (the clear area between the
cell membrane and the nucleus), nucleus, and in some cells a small clear vacuole. To see all parts of
Amoeba cells, it will be important to focus with the fine adjustment continually while observing these cells
because different cell parts are at different depths within the cell.
Questions:
1. How are Amoeba like animals? How are they not like animals? (Hink: Think about the number of cells
that make up a single organism.)
2. Why is observing and drawing multiple cells considered a reliability measure?
Part 2: Human Skin Cells (Animal Cells):
Read the procedure for Part 2 to answer the following prelab questions:
Prelab Questions:
1. On what power will you draw the cheek cells?]
2. How many cheek cells will you draw?
3. What kind of a cell is a cheek cell?
It is easy and painless to obtain epithelial skin cells from inside of the cheek!
 Put on a pair of goggles.
 Clean and dry a slide and cover slip.
 Discard the slide and/or cover slip if either of them is scratched.
 Place 1 drop of water on a clean glass slide.
 Scrape the inside of your cheek gently with the side of a clean toothpick. The loose epithelial cells will
come off onto the end of the toothpick. You will not be able to see them on the toothpick.
2
General Biology








Place the toothpick end, with the cells, into the water on your slide.
Tap the toothpick against the slide and swirl it around in the water until the water becomes slightly
cloudy.
Add 1 full drop of iodine to the drop (make sure your are wearing your goggles).
Add a cover slip.
Examine slide on low power. Bring the cells into focus. They will appear irregular in shape and some
will be found in clusters.
Switch to medium power and scan to find various cheek cells. The nucleus will be stained darkest and
will be very apparent. Find a few typical cheek cells.
Switch to high power to examine them in more detail. Find the following: Nucleus, Cell Membrane,
Cytoplasm.
On high power, draw 3 different cheeks cells . Follow lab drawing rules. In one cell, label all the parts
you observed. Attach these lab drawings in your lab notebook. When you are done, let your teacher
know you are ready to be considered for a full-credit stamp.
Question:
3. A validity measure is something that is done to increase the likelihood of getting accurate data. Why is
cleaning the slide an example of a validity measure?
Plant cells
You will work as a pair using one slide, however keep in mind that you will be tested on your skills of focusing
with the microscope, so both of you should be practicing. You are encouraged to discuss and compare what you
see with the other lab group at your lab table.
13. Is the cell wall of the elodea green?
14. What should a chloroplast look like?
15. Can you see the cell membrane?
16. How can you tell you are looking the large, clear water-filled vacuole?
17. What does cytoplasm look like?
18. What magnification do you use to draw your elodea cells?
19. How many cells will you draw?
20. How many times do you label each cell part?
Part 1: Elodea:
This green water plant will be placed in a culture dish in your tray at your station. It must remain in water at all
times except when you are removing a single leaf from the plant.
Examine the leaf without the microscope.
Question:
4. Describe how the leaf looks without using a microscope?
3
General Biology
Then make a wet mount of a single leaf as follows:







Clean and dry the slide and cover slip.
Put 1 or 2 drops of water on your slide first. This is done so that the leaf doesn’t have a chance to dry out.
Pick one green healthy-looking leaf from the tip of a sprig of Elodea and place it topside up (the darker
green side) in the water on the slide.
Add a cover slip. Make sure water doesn’t seep out and that aren’t any air bubbles.
Scan the cells in the leaf on low power.
Once you have found individual cells and have brought them into focus, move to medium power. If you
carefully focus, up and down, you will notice that this leaf is made of two layers of cells. If you do not focus
clearly on just the one layer of larger cells, you will see parts of both layers and this will confuse you. Focus
on the layer of large rectangular cells. Examine some cells near the vein of the leaf on 100X.
You should be able to find and identify the following structures:
Cell Wall
The thick outer layer covering of each cell. It is NOT green.
Chloroplasts
Chloroplasts are the oval green bodies seen throughout the cell. They capture light energy for use in
making sugar in photosynthesis.
Cell Membrane: You will not be able to see this because it is pressed against the inside of the cell wall.
Recognize that it would be found right inside of the cell wall.
Vacuole: The vacuole is a large, clear, water-filled sac in the center of the cytoplasm of the cell. It fills
most of the cell. It is visible only when you focus up and down to find a view of where the chloroplasts
appear around the edge of the cell only. It appears this way because a water-filled vacuole is surrounded
by the chloroplasts. With this in mind, try to find the vacuole. If you can’t see it, go on.
Cytoplasm: The clear, water-like substance in which the chloroplasts are floating. This is the clear
space between the chloroplasts and between the cell wall and the water vacuole.



Move to high power . You might be able to observe the chloroplasts moving.
On a half piece of white paper, draw 2 Elodea cells on high power. Follow lab drawing rules. In one cell,
label all the parts you observed. Attach these lab drawings in your lab notebook. When you are done, let
your teacher know you are ready to be considered for a full-credit stamp.
While you wait for your teacher to get to your station, answer the following numbered questions in your lab
notebook. Your answers must be in complete sentences (of course)!
Questions:
5. Are you collecting qualitative or quantitative data?
6. How do you know?
7. A “validity measure” makes your data more justifiable. What did you do to make your data more
reliable?
8. Why do you observe and draw more than one cell?
4
General Biology
9. Describe the movement of chloroplasts…if you saw them move. If not, wait until your teacher shows a
video clip on their movement and then describe their movement.

Use the green pencil in your tray to color the appropriately colored structures.
10. Chloroplasts cannot cause their own movement. They cannot swim or propel themselves in anyway.
Offer a hypothesis that would explain what causes them to move within the cytoplasm of the Elodea
cell.
Prelab Questions for Part 2: Read the procedure for Part 2 and answer the following questions:
1. What color is the epidermis that you will be observing?
2. How do you keep your onion skin from drying out?
3. What magnification will you be using to draw the onion cells.?
4. How many cells will you draw?
5. What cell part won’t you see?
Part 2: Onion Skin Cells:
You will find sections of red onion immersed in water in a culture dish in your tray.
 Remove one single scale of onion and return the rest of the onion section to the water.
 Hold this onion scale so that the concave surface is toward you. (Do you remember what “concave”
means?)
 Break the scale in half towards the purple side and a transparent, paper thin pink layer of onion epidermis
should become visible.
 Remove the onion epidermis by pulling it off the purple side of the onion scale. It’s like peeling dead skin
after a sunburn (yuck!).
 Prepare a wet mount as before so as to not to let your onion specimen dry out.
 THROW THE REMAINING SCALE IN THE GARBAGE!!!! DO NOT RETURN IT TO THE BOWL
WITH THE OTHER ONION SCALES.

 Examine the slide on low power to find cells and then bring these cells into focus. They should have a
long- hexagonal in shape, not round.
 Once it is in focus, switch to medium power and bring your specimen into focus.
Questions:
11. Make a list of the cell parts that you observe on medium power.
In the onion cells you should be able to see nuclei. They should appear as round dark objects, either in the
middle of the cell or at the edge of the cell.


Examine and scan many cells on medium power to find what seems to be typical cell.
Examine 2-3 typical cells on high power and locate each of the following:
o Cell Wall
o The cytoplasm will appear as a very thin, clear layer right inside of the cell wall.
o Vacuole- This area will be seen as pink area in a large portion of the center of the cell. The water
vacuole contains a pink pigment.
o The Cell membrane is pressed against the inside of the cell wall and will not be visible; therefore
you will not label it in your drawing.
5
General Biology


As with the Elodea cells, draw and label 3 typical onion cells under 400X. Follow lab drawing rules. In
one cell, label all the parts you observed. Use the red/pink pencil in your tray to color the appropriately
colored structures.
Attach these lab drawings in your lab notebook. When you are done, let your teacher know you are ready
to be considered for a full-credit stamp. While you are waiting answer the following question below your
drawing:
12. Where does the onion bulb grow in nature (above or below the ground)? Offer an explanation for why
the onion cells from the onion bulb do not contain chloroplasts. (Hint: The function of the chloroplasts
is to aid in photosynthesis. Photosynthesis is the process whereby chloroplasts in plant cells absorb light
and energy, which is used to make more plant cells. What is needed for photosynthesis to take place?)
Summary comparison of plant and animal cells
The remaining portion of this lab can be completed outside of class. To complete the following portion, you
will need your drawings of all cells made earlier in this lab.
If you were to examine a hundred more plant cells, you would find, in general, that all the plant cells would
resemble onion and elodea cells. Annimal and protest cells would, in general, resemble the cheek cells and
Amoebas. Use your cell drawings to answer the following questions after where you have attached your lab
drawings:
*Questions:
13. How does the basic general shape of the plant cells differ from the general shape of the animal cells?
14. What cellular structures are found in green plant cells only? (Elodea is the example.)
15. What structures are present in every plant and animal cell?
16. Restate the cell theory in your own words.

In your lab notebook, following the lab drawing rules, draw a generalized green plant cell and a generalized
animal cell based on the information you discovered in this lab. Title each cell (without total magnification)
.Label the parts that are contained in each cell that you found in the lab. Do not use the book or another
resource to help you with this. These drawings will be generalized and should not specifically resemble one
of the types of cell you saw in the lab.
There are many important cell structures that cannot be seen with a light microscope like yours. These
structures have been photographed with electron microscopes. You will learn about these structures later. At
that time, you will also learn more about the functions of the cell parts that you identified in this lab.
6