Download Comparing Plant and Animal Cells Lab

Name:____________________Hour:_______
Comparing Plant and Animal Cells Lab
Objectives: In this lab you will observe cell structures, compare and contrast animal and plant
cells and relate the structure of a cell to its function.
Materials: Prepared slides, microscope, toothpick, onion, Elodea plant in water, methylene
blue, iodine solution, paper towel
Procedure:
Part 1: Plant Cells
Onions are organized tissue that, under appropriate conditions, will give rise to an entire plant.
You may not know it, but they grow underground in the dirt, with their green leafy tops sticking
up out of the ground.
The curved layers or pieces that pull apart from a slice of onion are called scales. On the
underside of each scale is a thin membrane called the epidermis.
A. Obtain a piece of onion and remove one of the scales from it. Use forceps (tweezers) to pull
away the thin epidermis from the inner surface. Be careful not to wrinkle the membrane. Place
a drop of water on the center of a microscope slide and cut a very small square piece of onion
membrane. Using a toothpick to straighten out any wrinkles, place the membrane sample in the
drop of water. Take a cover slip and carefully place it over the sample, lowering it at an angle
to the slide.
B Examine the onion epidermis under low and high power. Unstained specimens are often
seen with less light so try turning down the amount of light using your diaphragm. Draw (TO
SCALE) what you see under low and high power. Be sure to label the magnification of each
drawing.
2 points
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QUESTION 1 – How many layers thick does the onion epidermis appear to be? (use
your fine adjustment knob for looking for the layers) 1 point ________________
QUESTION 2 – What is the general shape of a typical cell? 1 point _______________
C. To stain your specimen, remove your slide from the microscope. Gently lift the coverslip
off of the onion cell specimen and carefully blot the water from the specimen with a paper
towel. Place two drops of iodine solution on the onion cells and replace the coverslip. Allow
the iodine to soak into the onion for two minutes before observing the cell under the
microscope. Draw the cells again as you did before. 2 points
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QUESTION 3 – Label the following structures in the cell drawings above: nucleus, cell
wall, and cytoplasm. 3 points
D. Obtain a single leaf of Elodea (from the young leaves at the tip) and prepare a wet mount as
you did before but without iodine. Again, draw the specimens under low and high power.
Also, take notice of the way it looks under medium power as well. 2 points
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QUESTION 4 – Are the chloroplasts moving or stationary? 1 point
QUESTION 5 – In what ways are the cells of onion epidermis and Elodea similar?
Different? 2 points
QUESTION 6 – There were many chloroplasts in the Elodea cell, but what about the
onion cell? Did you see them?________ EXPLAIN why or why not.
1 point
Part 2: Animal Cells
E. Prepare a slide of check cells from your oral cavity by the following procedure. Place a drop
of methylene blue on a glass slide. Take a flat toothpick ( a NEW one ) and using the large end,
gently scrape the inside of your cheek 3 or 4 times. Do not GOUGE. Cells fall off on the inside
of your mouth all the time, and that is what you’re after. They are microscopic so you won’t
necessarily see them on the toothpick. Gently mix the end of the toothpick with the methylene
blue dye. Take a coverslip and carefully place it over the sample, lowering it at an angle to the
slide.
F. Examine and draw the cells under low and high power. Be sure to draw the cells to scale as
you see them in the microscope’s field of view. 2 points
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QUESTION 7 – Label the cell membrane, nucleus, and cytoplasm in the cells you
drew above. 3 points
QUESTION 8 – Inside the mouth, these cells are joined together in a sheet. Why are
they scattered here? 1 point
G. Prepared animal cell slide: obtain a prepared slide of animal cells. Again, draw the
specimens under low and high power. Also, take notice of the way it
looks under medium power as well. 2 points
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QUESTION 9 – Label the cell membrane, nucleus, and cytoplasm in the cells you
drew above. 3 points
QUESTION 10 – What is the relationship between plant cell structure and the ability of
plants to stand upright without bones? 1 point
PART 3: BACTERIA CELL
H. Bacteria cells: obtain a prepared slide of bacteria cells. Again, draw the specimens
under low and high power. Also, take notice of the way it looks under medium
power as well. 2 points
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QUESTION 11- What is one way bacteria cells are similar to plant cells? 1 point
QUESTION 12-
QUESTION 13 – How are these animal cells different from the plant cells you
observed? Fill in the graphic organizer on your answer sheet. YOU
MAY NEED YOUR NOTES! 7 points