Download Cell Structure Lab

HONORS BIOLOGY I
Cell Structure
INTRODUCTION:
Although there are great differences in the size, shape, color, and activities
of living things, the basic building units of all life have much in common. In
this investigation, you will see what some cells look like and compare the
structure and organization of cells from different organisms.
MATERIALS:
onion
spider plant leaf
cover slip
iodine
tropical plant leaf
toothpick
forceps
microscope
slide
PROCEDURE:
1.
Hold a piece of an onion "scale" leaf so that the concave surface faces
you and snap it backwards. A transparent, paper-thin layer of cells can
be seen along the outer curve of the scale.
2.
Using forceps or your fingernails peel off a small section of this thin
layer and place on a microscope slide with a coverslip on top.
3.
Place 1 drop of iodine on the edge of the coverslip and allow the stain to
reach most of the thin layer.
4.
Examine the slide first with medium power and then with high.
5.
Use a pencil for all drawings. Sketch a few cells in high power as they
would appear if you could see three dimensions. Label the cell wall, cell
membrane, nucleus, and cytoplasm.
6.
Mount a spider plant leaf on a slide and observe it on low power and then
with medium power. Sketch a few cells as they appear under medium
power. Label the cell wall, cell membrane, nucleus, cytoplasm and
chloroplasts.
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7.
Mount a tropical plant leaf on a slide and observe it on low power and
then with medium power. Sketch a few cells as they appear under
medium power. Label the cell wall, cell membrane, nucleus, cytoplasm
and chloroplasts.
8.
With the broad end of a toothpick, gently scrape the inside of your
cheek. It may be in clumps. (Scratching or digging into the cheek tissue
is not necessary.) Lay the broad end of the toothpick with the cheek
scraping in a drop of iodine on a slide. Roll the toothpick gently to
dislodge the cheek cells. Discard the toothpick. Add a cover slip and
examine the cheek cells with the medium and then high power of the
microscope. Find a field where the cells are separate and distinct and
sketch a few under high power. Label the cell membrane, cytoplasm, and
nucleus.
OBSERVATIONS:
ONION CELL-HIGH POWER
SPIDER
TROPICAL
CHEEK
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DISCUSSION:
1. In the tropical plant and spider plant, what things are not visible? Why?
2. What cell part did you find around plant cells that you did not find around
your cheek cells?
3. Why is it difficult to see the cell membrane in plant cells?
4. How did the iodine help? Why do you suppose biologists use different
kinds of stains on cells they are studying under the microscope?
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