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Background
Ever since the first microscope w as used , biologists have been interested in stud ying the cellular
organization of all living things. After hund red s of years of observations by m any biologists, the cell t heory
w as d eveloped . The cell theory states that the cell is the structural and functional unit of living things. One w ay
cells are classified is by the structures they contain.
All cells contain 3 parts; cytoplasm , genetic m aterial, and a m em brane. H ow ever, d ifferent types of
organism s like prokaryotes and eukaryotes have d ifferent organelles. Ad d itionally, even d ifferent
eukaryotic organism s like plants and anim als have d ifferences in their cells. In plant and anim al cells, both
sim ilarities and d ifferences exist w ith respect to structure. In this investigation, you w ill com pare the
structures of a typical bacteria (prokaryote) cell, plant cell and anim al cell (eukaryote cells).
Focus Questions
By the end of this lab, you should be able to answ er the follow ing questions
1. What are the proper techniques of using a m icroscope and preparing slid es
2. What structures d o cells contain?
3. H ow are plant, anim al, and bacterial cells alike? H ow are they d ifferen t?
Pre-Lab Questions
1. What is cell theory?
2. What d o all cells contain?
3. What is a prokaryote?
4. What is a eukaryote?
5. What is an organelle?
Materials
• Forceps • Micro d ropping pipet • Water plant leaf • Water • Microscope • Glass slid e
• Coverslip • Toothpicks • Methylene blue stain • Paper tow el • Lens paper
Safety
Use caution w hen hand ling glass slid es as they can break easily and cut you. Alw ays use special caution
w hen w orking w ith laboratory chem icals, as they m ay irritate the sk in or cause staining of skin or clothing.
N ever touch or taste any chem ical unless instructed to d o so.
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Procedure
 Part A. Examining Prokaryotic Cells - Bacteria
A few select fixed bacterial slid es are available for you to view . Slid es are labeled w ith the species
represented , or source of sm ear. These slid es feature heat -fixed , d ead bacteria cells that have been stained
to m ake view ing them easier. You are not expected to see a nucleus. Why?
Proced ures:
With your group, place the m icroscope about 10 cm Flow Chart:
from the ed ge of the laboratory table.
Obtain a fixed bacterial slid e. To view a slid e:
a) if need ed , clean any sm ud ges by lightly buffing
the slid e w ith lens paper.
b) place the slid e on your stage w ith the m ost
highly stained region of the slid e d irectly over the
opening in the stage.
c) Focus the slid e using the 4x (low -pow er)
objective lens. Proceed to 10x (m ed -pow er) and
finally, only after the stained sm ear is in focus,
focus a section of the slide on 40x (high -pow er).
Once the sm ear/ cells are in focus on high -pow er,
select a section of a few cells and d raw them in
Data Table 1.
Id entify and label im portant structures on one of
the cells in your d raw ing.
Return the slid e to the d esignated area and repeat
the above proced ures for 2 ad d itional bacterial
slid es.
Proceed to Part B
D ata Table 1
Slide N ame:
Slide N ame:
Slide N ame:
D
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a
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n
g
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Comparing Cells Lab
Part B. Examining Eukaryotic Cells – Plant Cells
1. Obtain a glass slid e, a coverslip, and a forceps.
2. Using the d ropping pipet, place a d rop of w ater in the
center of your clean glass slid e.
3. Using the forceps, rem ove a leaf from the supplied
w ater plant and place the leaf on the d rop of w ater on
the slid e – BOTTON SIDE OF LEAF UP. Make sure
that the leaf is flat and not fold ed .
4. Carefully place a coverslip over leaf, and press d ow n
gently until the leaf is perfectly flat, no airbubbles.
5. Place the slid e on the stage of the m icroscope w ith the
leaf d irectly over the opening in the stage.
6. Using the 4x (low -pow er) objective lens, locate the leaf
by turning the coarse ad justm ent knob until the leaf
com es into focus.
7. Sw itch to the 10x (m ed -pow er). Use the fine focus
knob to ad just your view .
8. Sw itch to the 40x (high-pow er) objective lens. Use the
fine focus knob to ad just your view . At this
m agnification sm all ad justm ents of the fine focus knob
w ill allow you to w itness the 3-d im ensionality of the
leaf, as the leaf is com posed of m any layers of cells.
You can focus on as m any as three d ifferent layers of
cells, by sim ply scrolling ‘ up’ or ‘ d ow n’ w ith the
fine focus ad justm ent.
9. Closely observe the cells of the leaf. Com plete Data
Table 2 by d raw ing a section of plant cells and labeling
all im portant structures/ organelles you see.
10. When your lab group has finished using your leaf
slid e, rem ove the coverslip, throw aw ay the leaf, rinse
and pat-d ry both your slid e and coverslip – then return
your slid e and coverslip to w here they belong.
D ata Table 2
D raw three cells in a single row at 400x
- label each structure/ organelle you can see
for one of the cells -
Flow Chart:
Additional D ata
1. Thoroughly d escribe these plant cells and their
pattern w ithin a leaf.
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Comparing Cells Lab
Part C. Examining Eukaryotic Cells – Human Cheek Cells
1. Using a m icro d ropping pipet, place a very sm all
Flow Chart
d rop of w ater in the center of a clean glass slid e.
2. Using the end of a toothpick, gently scrape the
insid e of your cheek. CAUTION : Do not use force
when scraping the inside of your cheek. The end of the
toothpick has m any cheek cells stuck to it, though
you m ay see nothing.
3. Stir the w ater on the slid e w ith the end of the
toothpick to m ix the cheek cells w ith the w ater. (See
Figure 2).D ISPOSE of the toothpick in the trashcan.
4. Put one small d rop of methylene blue stain on top
of the d rop of w ater containing the cheek
cells.CAUTION : methylene blue stainins hands and
clothing.
5. Wait one m inute, and then carefully place a
coverslip over the stained cheek cells.
6. To rem ove the stain from und er the coverslip and
replace it w ith clear w ater, place a piece of paper
tow el at the ed ge of one sid e of the coverslip. Then
place a very sm all d rop of w ater at the ed ge of the
coverslip on the opposite sid e. (See Figure 3). The
paper tow el w ill absorb the stained w ater und er the
coverslip. As the stain is rem oved , the clear w ater
next to the coverslip on the opposite sid e w ill be
d raw n u nd er the coverslip. Discard the paper tow el
after it has absorbed the stained w ater.
7. Place the slid e on the stage of the m icroscope w ith
the center of the coverslip d irectly over the opening
in the stage.
8. Using the low -pow er objective lens, locate the
region of the slid e w ith a fairly high concentration
of cheek cells. N ote: Y ou may need to reduce the
amount of light coming through the slide in order to see
the cells more clearly. A djust the diaphragm as
necessary.
9. Sw itch to the m ed ium pow er, and then the high pow er objective lens.
10. Observe a few cheek cells at 400x. Select tw o
d ifferent looking cheek cells. Draw each cell in Data
Table 3. Label all im portant structures/ organelles
you see.
11. Carefully rinse, d ry, and return your coverslip and
slid e.
Figure 2
Figure 3
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Comparing Cells Lab
D ata Table 3
D raw an enlarged view of one cheek cell
- label each structure/ organelle you can see -
Additional D ata
Thoroughly d escribe this anim al cell.
D raw an enlarged view of another cheek cell
- label each structure/ organelle you can see -
Additional D ata
Thoroughly d escribe this anim al cell.
Analysis and Conclusion Questions
Directions: Answ er the follow ing questions using complete sentences.
1. Consid er all 3 cell types observed in this lab. Based on your observations, d escribe the d ifferences
you observed betw een prokaryotic (bacteria) and eukaryotic (plant and anim al) cells.
2. Consid er the eukaryotic cells you observed in this lab. Based on your observations, d escribe the
sim ilarities you observed betw een plant and anim al cells.
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Comparing Cells Lab
3. Consid er the eukaryotic cells you observed in this lab. If you w ere given a slid e containing living
cells of an unknow n organism , how w ould you id entify the cells as either plant or anim al? *note: be
very thorough and include in your answer a full description of every structure, and characteristic, one would
expect to be able to use to differentiate between plant and animal cells.
4. Why is it an ad vantage to use a w et-m ount preparation instead of a d ry-mount preparation in the
stud y of living cells?
5. Why are stains often used w hen observing cells und er the m icroscope?
6. Explain w hy you think an oak tree leaf w as not chosen for the plant cell part of this lab.
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Comparing Cells Lab