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Cell Structure
“The Basic Unit of Life”
1. In 1665, Robert Hooke, an English Scientist, reported an interesting observation
while looking through his microscope at cork. “I took a good clear piece of cork,
and with a penknife sharpened as keen as a razor, I cut a piece of it off, then
examining it with a microscope, me thought I could perceive it to appear a little
porous, much like a honeycomb, but that the pores were not regular”
a. What were the honey comb units at which Hooke was looking? ____________
b. What specific cell part was all that was left of the cork? __________________
2. a. Is cork produced by a plant or an animal? _____________________________
b. Do animals have cell walls? ________________________________________
3. Look up the name of the chemical which makes up the cell wall. _____________
____________________________________________________________________
Part B. Cell Membrane and Cytoplasm
Human cheek cells may be used for viewing the cell membrane and cytoplasm. A cell
membrane is a thin outer boundary which surrounds the cell and separates it from
neighboring cells. Cytoplasm is the jellylike inner portion of the cell.
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Place a drop of Methlyene Blue Stain onto a slide.
Gently scrape the inside of your cheek with the end of a toothpick. You will not be
able to see anything on the end of the toothpick when you remove it from your
mouth.
Dip the toothpick into the stain on the slide and mix once or twice.
Add a coverslip and examine under low and high power of your microscope.
Locate and examine cells that are separates from one another than those that are in
clumps.
On the summary sheet, draw several cheek cells as they appear under high
magnification. Label the cell membrane and cytoplasm and nucleus!
Part B. Cell Membrane and Cytoplasm
1. Use the space below to draw several cheek cells as they appear under high
magnification. Label the cell membrane and cytoplasm.
2. Describe the shape of a cheek cell. _________________________________________
3. a. Are cheek cells produced by plants or animals? _____________________________
b. Is a cell wall present? _________________________________________________
4. Are cheek cells alive? ___________________________________________________
5. Describe the location of the cell membrane? _________________________________
6. What is the primary function of the cell membrane? ___________________________
_______________________________________________________________________
7. a. Describe the location of the cell’s cytoplasm. ______________________________
b. Describe the appearance of cytoplasm. ___________________________________
8. What is the function of a cell’s cytoplasm? __________________________________
9. Why was a stain added to the cheek cells? ___________________________________
10. Do you have evidence that living things (or once living things) are composed of basic
units called cells? ____________ Explain. _____________________________________
_______________________________________________________________________
Part C. Cell Nucleus and Nucleolus
Onion cells may be used to show a cell’s nucleus and nucleolus. These two structures
occur within most living cells. There may be several nucleoli appearing as dots within
each cell’s nucleus. The nucleus will appear as a round structure inside each cell.
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Snap an onion bulb scale in half.
Use your fingernail to peel off a thin layer of onion tissue.
Place one thin onion layer onto a microscope slide.
Uncurl or unfold any overlapped portion of the onion layer. Make sure the layer is
perfectly flat. Add a drop of iodine stain to the onion. Add a coverslip to the onion.
Tap the coverslip gently with the eraser end of a pencil to drive out any air bubbles.
Observe the cells under both low and high power of your microscope. Note the brick
wall appearance of the cells with cell walls separating the cells.
Locate a small round structure, the nucleus, within each cell. Examine a nucleus
carefully by focusing up and down through the cell
With high power, observe the tiny dots within the nucleus. These are nucleoli.
On the summary sheet, draw a single onion cell as it appears under high power.
Label the cell wall, nucleus, nucleolus, and nuclear membrane.
Part C. Cell Nucleus and Nucleolus
1. Diagram a single onion cell in the space provided as it appears under high power.
Label the cell wall, nucleus, nucleolus, and nuclear membrane.
2. Describe the shape of an onion cell? ________________________________________
3. a. Are onion cells produced by plants or animals? _____________________________
b. Is a cell wall present? __________________________________________________
4. a. Describe the shape of the nucleus of an onion cell. ___________________________
b. Within what cell part already studied does the nucleus lie? ____________________
5. What is the function of a cell’s nucleus? _____________________________________
6. a. Describe the shape of the nucleolus of an onion cell __________________________
b. Where is the nucleolus found? ___________________________________________
7. What is the function of the cell’s nucleus? ___________________________________
8. What structure separates the contents of the nucleus from the cytoplasm? ___________
_______________________________________________________________________
9. Why were the cells stained? _______________________________________________
Part D. Chloroplasts
Another cell part found in the cells of many producers is the green chloroplast. Elodea a
common water plant shows there important structures well.
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Prepare a wet mount of an Elodea leaflet.
Using low power of your microscope, position your slide so you are looking near the
edge of the leaflet. Locate green, oblong cells. Examine these cells under high power.
3. Note the small green organelles inside each cell. These are chloroplasts. Movement
of the chloroplasts within the cell often can be observed. This is called “cytoplasmic
streaming”.
4. Label the cell wall, chloroplast, cytoplasm, and cell membrane.
Part D. Chloroplasts
1. Diagram a single Elodea cell in the space provided. Use high power. Label the cell
wall, chloroplast, cytoplasm, and cell membrane.
2. Describe the shape of an Elodea cell. _______________________________________
3. a. Is elodea a plant or animal? ____________________________________________
b. Is a cell wall present? _________________________________________________
4. Describe the…
a. color of the chloroplasts. _______________________________________________
b. shape of the chloroplasts. _______________________________________________
5. Within what cell part already studied do chloroplasts lie? _______________________
6. What is the function of chloroplasts? _______________________________________
7. Are chloroplasts usually present in consumer cells? ___________________________
Plasmolysis in Elodea cells
Part I:
1. Place a small drop of water on the slide.
2. Obtain a small leaf from the Elodea plant and place on the slide.
Your forceps will help in placing the leaf on the slide.
3. Place the coverslip on your specimen.
4. Observe under low power.
5. Next, examine your specimen under high power and draw what you see.
Label the following cell structures: cell wall, nucleus, chloroplasts, and cell membrane.
***Note: The chloroplasts are the numerous green organelles in each cell. Carefully
observe the location of the chloroplasts in relation to the cell wall
Part I Elodea Specimen
Part II Elodea Specimen
High power
High Power
Total Mag._______
Total Mag.________
Tap water sample
Plasmolyzed Cell
DO NOT CLEAN YOUR SLIDE- USE THE SAME SLIDE FOR PART II- KEEP
YOUR SLIDE ON THE STAGE OF YOUR MICROSCOPE!!!!!!
Part II. Plasmolysis of Elodea- hypertonic solutions
6. Next, raise the objective of your microscope to obtain ample clearance from your slide!
7. Obtain a dropper and obtain some of the 6% salt solution at your station.
8. Next, place 3 drops of 6% salt water to the right of the coverslip. Tear off a portion of
paper towel, place it to the left of your coverslip and pull the salt water solution through.
9. Wait 2 or 3 minutes. Observe this leaf under high power.
10. Carefully observe the location of chloroplasts in relation to the cell wall. Compare
this to your slide in Part I.
11. Draw what you see and label the following: cell wall, chloroplast (Do you see a cell
membrane?)
Describe the location of chloroplasts in a normal Elodea cell (in tap water).
Describe the location of chloroplasts in a plasmolyzed cell (in salt water).
Using your Part I and Part II information:
Read the following four statements before answering the questions:
a) Elodea cells normally contain 1% salt and 99% water on the inside.
b) Tap water used in this investigation contains 1% salt and 99% water.
c) Salt water used in this investigation contains 6% salt and 94% water.
d) Salt water has a higher concentration of salt than fresh water or Elodea
cells.
1. What is the percentage of water outside the cell at the investigation’s
start? ________________________________________________________
2. What is the percentage of water inside the cell at the investigation’s
start?
_________________________________________________________
3. Is the percentage of water (concentration) inside high or lower than the
percentage outside?
____________________________________________
4. When will the water move across the cell’s membrane? _____________
____________________________________________________________
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5. Circle the direction water should move: from High to Low or Low to
High concentration.
6. Did the inside of the cell change shape due to water loss? ____________
explain: ____________________________________________________
What is plasmolysis?
General Analysis
Complete this chart by checking the appropriate spaces to indicate if that part is found in
plant or animal cells.
Nucleus
Animal
Plant
Cell
Wall
Cytoplasm
Nuclear
Nucleolus Chloroplasts
Cell
Membrane
Membrane