Cell Lab
Make a wet mount of onion cells by adding IODINE instead of water.
Plant cells: Elodea and Onion
Make a wet mount of a single elodea leaf. Make your way to 40x.
Look for the same cell parts.
Q: What do you immediately notice (see) that makes this “object”
different than the objects you viewed in the microscope lab?
See if you can find a nucleus (holds the genetic material (DNA)) in
some cells. (Every onion cell has a nucleus, but they don’t always
absorb the iodine stain so they may be difficult to see.)
Notice that the leaf is made of two layers of transparent cells. Focus
on the layer of large cells. See if you can locate the following
structures (Check those that you see.):
_____ Cell Wall: Thick outer covering of each cell.
_____ Chloroplasts: Green disks. They turn light into sugar through
a process called photosynthesis.
_____ Cytoplasm: The clear fluid in each cell.
_____ Cell Membrane: Pressed against the cell wall, so it is NOT
visible. Remember that it is there.
_____ Vacuole: Water-filled sac found in the middle. If you can’t see
it directly, see if you can observe it indirectly by noting the
chloroplasts sitting around its edge.
Notice that the cytoplasm may appear “grainy” in some areas.
Vacuoles are the “clear” areas of the cell, and they take up most of the
center of the cell. The membrane surrounding the vacuole may be
difficult to see.
Again, the cell membrane is pushed up against the cell wall and will
NOT be visible. Don’t forget that it IS there.
Make a drawing of 3 onion cells that take up most of the circle. Label
the parts that you could see.
Now observe cells near the vein of the leaf.
Q: Can you spot any chloroplasts that are moving? If yes, describe
how they are moving. If you’ve really searched and couldn’t find any,
just say so.
Using your colored pencils,
draw one elodea cell so that
your drawing stretches across
the circle. Label only the parts
that you found.
Q: Chloroplasts have no way of
moving on their own.
Hypothesize: Why are they
moving?
Q: Hypothesize: Remembering where onions come from, why don’t
onions have chloroplasts?
Animal Cells: Human Cheek Cells and Amoeba
Gently scrape the inside of your cheek with a toothpick, and smear the
toothpick on a clean slide. Add one drop of iodine.
After scanning on 4x and 10x, look at a few cheek cells under 40x.
Notice the following:
_____ NO cell wall.
_____ Cell Membrane: the soft outer covering of animal cells;
controls what enters and leaves the cell
_____ Nucleus
_____ Cytoplasm (clear)
Draw and label two cheek
cells so they stretch across
the circle.
QUESTIONS:
1. Why were you not able to see a nucleus in some cells?
2. What is the difference in function between cells that have
chloroplasts and those that do not?
3. Which organelle usually present in plant cells is absent in the
stained onion skin tissue?
4. Which cell part is common to both the onion skin cells and the
elodea leaf cells?
5. In what ways do animal cells resemble plant cells?
6. In what ways do animal cells differ from plant cells?
a.)
Watch an Amoeba projected on the classroom screen.
An Amoeba has a
changing structure called a
pseudopod (“false foot”)
that helps it move and
capture prey. Watch a
pseudopod changing.
Draw and label one
amoeba. (Cell membrane,
cytoplasm, nucleus,
vacuole, pseudopod)
b.)
c.)
7. Draw and label a generalized plant cell in one circle and an animal
cell in the other.