Show
ImageJ application.
Go
to File, Open Samples and open the image Cheek
Cell. There are a couple of cells shown along with a scale in the
lower left corner. This scale was obtained by photographing a micrometer
slide (shown on the left) under the microscope at the same magnification
as the onion cell. Then a 10 micron portion of the scale was selected with
the Rectangle Selection tool 
and copied using the command under Edit in the Menu. It was then pasted
on the cheek cell image using the Paste under the Edit Menu. The Text A
tool was used to put on the label. Observe the nuclei present in the two
cells.
Calibrating
the image.
Go to your
Line 
tool. Drag
the tool across the scale bar. Then go to Set Scale under
Analyze. Put micrometers for "Unit of Measurement"
and 10 for "Known Distance". Then
go to Set Measurements under Analyze and only
check "Area" and "Perimeter".
Using this same Line
tool measure the greatest length of the upper cell. (Once you have drawn
the line select Measure under Analyze and you
will have the length in micrometers.) Record your results in Table
1. Do the same thing for the lower cell. Then use the Freehand
Tool and trace around
the two cells to calculate the area. Record results in Table
1.
Close
Cheek Cell and Open Images Epi1000 and Ep1500. The
cheek cells that you have been looking at are called Epithelial Cells.
They are the cells that cover your skin and line the internal cavities of
the body. These are scanning electron micrographs SEMs of cheek cells that
are magnified either 1000 or 1500 times. Calibrate
Ep1500 using the technique that was described above. Measure
the greatest length as well as the area of the cell shown under 1500X and
enter the information in Table 2.
1. Compare
this length with your other two light microscope lengths.
2. What is
the percent difference between this length measurement and an average of
the other two values? (Percent difference is determined by dividing the
difference between the SEM length and the calculated the average of the
two light microscope values and then multiplying this difference by 100.)
(Show your calculations)
Onion Cell:
Open
Open Samples, Onion Cell.
3.
What is the most prominent cellular difference between these plant cells
and the cheek cells.
4. If this
is a plant cell, what two structures are not present?
If you look
closely you may be able to see several nucleoli inside each nucleus.
Keep
Onion Cell open and also open Scale This Scale
image is a photograph of a micrometer slide that you saw earlier on this
page. The large gap is 0.1 mm. or 100 micrometers. The closely spaced lines
on the left are 10 micrometers apart. Go up to Image on the Menubar and
select Type, 8-bit Grayscale. Use the Rectangle Selection 
tool and copy a 10 µ area. (It should look like the piece that
is immediately above the label 10 microns. Notice how the selection is made
through the middle of the micrometer line to middle for the next line.)
5. Why is the
copy portion selected in this manner?
Paste
the 10 micron portion in the lower left portion 
of
the Onion Cell image.
Calibrating
the image.
Follow the
same procedure that you used earlier. Measure the area and perimeter (Length)
of the cell that is in the center and Record results in Table 3. Measure
the perimeter of the nucleus of this center cell.
6. Compare
the nuclear area to the area of the entire cell as a percentage. How accurate
a method is this for determining the size of a nucleus in the cell?
Reference The
follow are WEB reference sites for information
on Epithelial Cells. This
site on Epithelial
cells describes their general characteristics and has light microscope
photographs.
Results(You
can also Go to File, Open Samples and Open the
image Results which is a copy of this Results section. While
this page cannot be printed out - at this time - it can be saved as a JPEG
file to your desktop. You can then open it with any graphics program,type
out the answers and then print it out from your program. You
can also enter the results on this image using the Text 
Tool. To do this first go to Edit, Options, Fonts and select something
like Geneva - 12 pt - Bold. Then click on the Results Image
in the answer space and draw out the yellow rectangle that appears and start
typing. When you are finished go to Edit and Select
Draw. What you have typed should now be present.)
Table
1:
1. Compare this length
with your other two light microscope lengths.
2. What is the % difference
between the light microscope length measurements and the SEM length measurement?
(Show your calculations) Comment on possible reasons for the difference.
3. What is the most
prominent cellular difference between these plant cells and the cheek cells.
4. If this is a plant
cell, what two structures are not present?
5. Why is the copy
portion selected in this manner?
Table
2 :
6. Compare the nuclear
area to the area of the entire cell as a %. How accurate a method is this
for determining the size of a nucleus in the cell?
There are distinct structural as well as physiological differences between plant and animal cells. In this exercise we will examine human cheek cells and compare them with cells obtained from an onion.
