CYTOLOGY LAB ACITIVITY
PART III
PLANT CELLS
PURPOSE
To acquaint with the structure of plant cells and the function of certain cell organelles.
PRE-LAB
MAKING BIOLOGICAL DIAGRAMS
Biological Diagrams Checklist
Used a blank white piece of paper on one side only
Diagram drawn with a sharp, hard pencil (HB 2 or HB4)
Diagram drawn with clear fine lines (no sketching)
Double fine lines are used to indicate the thick cell wall
Diagram is large enough to show the details
Diagram is not shaded or coloured (stippling used)
Drew only what I saw
Labels are all to the right of the diagram
My label lines are straight and clear because I used a ruler
My label lines have no arrow heads
All important structures are labeled
I used singular form for the labels (e.g. chloroplast and not
chloroplasts, mitochondrion and not mitochondria)
My labels are not too close to the diagram
I connected my labels to appropriate parts
Since my drawing is of microscope observations, I have
indicated the magnification
My diagram has an appropriate title
MATERIALS
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Light Microscope
Lens paper
Microscope slide
Cover slip
Cornstarch
Onion
Dropping pipette
Beaker, 50 mL
Scalpel
Tomato
Sugar
Tweezers
Potato
Toothpicks
Methylene blue stain
Iodine stain
Celery
PROCEDURE
Part 1:
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Squash Preparation of Tomato
Using a toothpick, remove a small amount of pulp from underneath the skin of a tomato.
Prepare a wet mount of the pulp.
Place the wet mount on the counter surface and gently press a folded piece of paper toweling on top of the
cover slip to squash the pulp and to spread it out on the slide.
Locate the tomato cells under low power and then switch to high powers. Remember that you may have
to adjust the diaphragm for optimum light conditions.
Add some methylene blue stain along on the edge of the cover slip and draw the stain under the cover slip
by placing a small piece of paper towel along the opposite edge of the slip.
Move the slide so that you can focus on a few cells clearly.
1. Sketch the tomato cells that you are observing and all of their organelles that you can resolve at mediumpower (or high-power if the cells are not too big). Label the parts of the cells that you recognize. If you see
small structures inside the cells containing dark red pigment then these are chromoplasts. (Chromoplasts are
plastids that contain pigments other than chlorophyll (green) or carotenoids (yellow orange). You should see
the large blue nucleus.
2. Estimate the size of a tomato cell and indicate how you determined this.
Measured size of low-power field Calculated size of mediumof view
power field of view
Calculated size of cell
Part 2:
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Squash Preparation of Potato
Use a scalpel, scrape off a small amount of the inside of a potato and place it on the slide and add a drop
of water.
Add a cover slip and observe under the microscope under high-power, adjust diaphragm for optimum
viewing.
Add some iodine stain along one edge of the cover slip and draw the stain under the cover slip by placing
a small piece of paper towel along the opposite edge of the slide.
Move the slide so that you can focus on a few cells clearly. Often, the best cells are near where the stain is
beginning to take effect.
3.
Draw and label cells Illustrating and labeling the membrane and leucoplasts (amyloplasts). Leucoplasts
are colourless plastids in the cytoplasm of plant cells. Leucoplasts store starch.
4.
Estimate the size of a potato cell and a leucoplast and indicate how you determined this.
Size of Cell
Size of Leucoplasts
Place a small amount of cornstarch on one end of s clean microscope slide and a small amount of sugar on the
other end
5.
What happens when you add a drop of iodine to the cornstarch? ….. to the sugar?
6.
What do you think is the function of the leucoplasts in the cell and explain your reasoning.
Part 3:
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Wet Mount Preparation of Celery Cells
Cut a small square (0.5 cm) with the scalpel on the back of a piece of celery.
Tease a very thin slice of the celery up with tweezers, peel off towards the end.
Place the specimen outside up with a drop of water on the slide.
Remove any part of the slice that appears to be thick
Cover with cover slip and observe under medium-power or high-power.
As you focus up and down you should observe two layers of cells. The cells in the outside layer
occasionally have two sausage shaped (Or bean shaped) cells surrounding an opening. This is a stomata
and the two cells are guard cells. Observe one of these guard cells under high-power.
7.
Sketch one of the guard cells and label all the organelles that you can resolve within the cell.
You should certainly see many chloroplasts in the cell which contain a green pigment called
chlorophyll.
8.
Estimate the size of a guard cell and size of a chloroplast and show how you determined this.
Size of Cell
9.
Size of Chloroplasts
Explain in detail how the guard cells regulate the air flow into the plant.
Part 4:
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10.
Obtain a small section of the scale of leaf of an onion
Use the scalpel to remove a single layer of epidermal cells from the inner (concave) side of the
scale leaf.
Place the epithelium piece in water on a slide. Ensure section is spread out and not folded.
Add a cover slip and view the slide under the microscope.
While viewing the cells under high-power, what level of light intensity reveals the most cellular
detail?
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Wet Mount Preparation of Onion Cells
Remove the slide from the microscope and add some methylene blue stain to the edge of the
cover slip.
Draw it under the cover slip by touching the opposite edge of the cover slip with a paper towel.
Sketch the arrangement of three or four adjacent cells while viewing under medium-power.
12. Sketch one cell under high-power and label all the structures that you can resolve (cell membrane,
nuclear membrane and content, cytoplasm and cell wall). Attempt to find a cell with a clear nucleus
and see if you can resolve the nucleolus within the nucleus.
13. Estimate the size of the nucleus and show your work!
QUESTIONS
14.
Research to determine the function of the chloroplasts.
15.
Research to determine the chemical equation of photosynthesis.
16.
Explain why onion cells did not contain any chloroplasts or certainly fewer than the guard cells
of the celery cells.
17.
What are two functions of the epithelial tissue on the outside of the celery stalk?
CYTOLOGY LAB ACITIVITY
PART IV
ANIMAL CELLS
PURPOSE
To acquaint with the structure of animal cells in order to enable you to compare their structure to plant
cells.
MATERIAL
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Light Microscope
Lens paper
Microscope slide
Cover slip
Blender
Dropping pipette
Beaker, 50 mL
Scalpel
Balance
Tweezers
Chicken wing
Toothpicks
Methylene blue stain
Liver
PROCEDURE
Part 1: Muscle Cell Examination
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Place a drop of methylene blue stain on a slide and allow it to dry.
Use the scalpel and tweezers to remove a small amount of the muscle fibres of the chicken wing.
Place the fibre on the dried methylene blue and add a drop of water and cover slip.
Use a folded paper towel to squash the fibres and then examine the slide under the powers.
1. Draw and label a composite animal cell with the following labels, cell membrane, cytoplasm, nucleus, nuclear
membrane and nucleolus.
Part 2: Maceration and Dilution of Liver
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Cut about 50 g of liver into many small pieces and place into a blender with approximately
100mL of cold water.
Operate the blender at high speed for about 30 s.
Add a drop of the liver suspension to a clean slide.
Examine the cells under low, medium and high-power.
2.
Draw a composite cell and label as many structures as you are able to resolve.
3.
Show your working to indicate the size of the cell.
Part 3: Human Cheek Cells
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Place a drop of methylene blue stain on a slide and a small piece of human hair to act as a
focusing guide.
Gently scrape the inside of your cheek with the end of a clean toothpick. You will not see
anything on the end of your toothpick when you remove it from your mouth.
Dip your toothpick into the stain on your slide and mix it about a couple of times.
Add a cover slip and examine those cells that are separate under low, medium and high-power.
4. Draw and label a typical cheek cell.
5. Estimate the thickness of the cell membrane in micrometers and show your work.
QUESTIONS
6. List as many differences that you have noted between plant and animal cells.
7. List as many similarities as you can of plant and animal cells.
8. Research to determine if all cells are like the typical plant and animal cells that you have observed in this
activity. What did you find?