Assignment 4
Due January 31
1. Fill-in-the-blanks (2 points)
Calculate the total magnifications using light microscopes with the eyepiece and objective lenses
indicated in the table below. Then answer the question in WebAssign.
Microscope Objective
lens
A
4X
B
10X
C
20X
D
40X
Eyepiece
lens
15X
15X
10X
10X
Total
magnification
2. Matching (2 points)
View these images of an onion root tip and rank them in order from lowest to highest
magnification. Match the image with its relative magnification, using the letter of the image for
identification. Then answer the question in WebAssign. (There is no partial credit for this
question—your score will be 0 or 2).
Relative
magnification
1 (lowest)
2
3
4 (highest)
Onion skin image
Image __
Image __
Image __
Image __
3. Multiple-choice (1 point)
Assume that the field of view at 400X total magnification (objective lens x eye piece lens) is
0.26 mm (260 microns). Determine the height (vertical dimension) of onion cells pictured below
from an image observed at 400X. Note: the cells different somewhat is size, so measure those
that seem most typical.
Cell size (vertical dimension) of these cells
is approximately
260 microns
130 microns
60 microns
25 microns
3 microns
4. Multiple-choice (1 point)
The image below is a human blood smear. Blood cells are relatively small, but white blood cells
are larger than red blood cells. Use the vertical lines grid in the video to measure the diameter of
the white blood cell (arrow). The image was captured using a video microscope with the 40X
objective lens. HINT: Be sure to use grid lines as viewed using the 40X lens.
Size of the white blood cell is
approximately
0.3 uM
3 uM
18 uM
30 uM
180 uM
5. File upload (1 point)
Utilize the virtual SEM at the Molecular Expression Microscopy Primer to obtain the best
possible image of the surface structures on a gecko foot at 3,000X magnification. (You will need
to adjust the controls.) Perform a screen capture of this image and upload it to WebAssign. Be
sure that the image format is .jpg or .png.
6. Essay (4 points)
Indicate whether the cells in the 4 images of plant tissue were viewed by a light microscopy,
transmission electron microscopy (TEM), or scanning electron microscopy (SEM). For full
credit you must justify your answers.
Type of
microscope used.
Briefly explain each answer.
Image A
Image B
Image C
Image D
7. File upload (2 points)
Download the TEM image of a bacterial cell (cross section) and label the following parts:
the plasma membrane
the cell wall
Upload the labeled image to WebAssign. Be sure that the image format is .jpg or .png.
8. Multiple-choice (1 point)
In the Gram staining procedure, bacteria were “fixed” by
placing the slide on a hot plate
passing the slide through a flame
pouring alcohol on the slide
rinsing the slide in tap water
waving the slide in the air
9. Multiple-choice (1 point)
In the Gram staining procedure, the purpose of safranin was to
stain the cell wall of Gram-positive bacteria
intensify the color of Gram-positive bacteria
decolorize the cell wall of Gram-negative bacteria
stain the cell wall of Gram-negative bacteria
none of these is the purpose of safranin
10. Essay (4 points)
Observe the images and diagrams that compare cell and organelle sizes. Then write a short essay
that answers the following questions:
How do most prokaryotes compare in size to small and large eukaryotic cells?
How does a mitochondrion compare in size to a nucleus and to a prokaryote?
You might use statements such as “cell X is almost 20x bigger than cell Y” or you could use this
grid image to obtain measurements. Try to incorporate information from both the images and the
diagrams. Most importantly, your essay should make clear the magnitude of size differences.
11. Essay (4 points)
View the videos in activity 3 and carefully observe the four living protists (two protists are
shown in video 1). Pick one protist from the first video and one protist from the either of the
other videos and describe how each protist moves. Are visible structures involved in locomotion?
Also, describe any internal organelles that are clearly visible.
12. Matching (5 points)
Match each cell structure in the liver cell to its name, using the word bank below. Then do the
same matching in WebAssign. Note that several names are not used.
Name of structure or organelle
Structure A
Structure B
Structure C
Structure D
Structure E
mitochondrion, chloroplast, nucleus, nucleolus, Golgi, ribosomes, vesicles, plasma membrane,
cell wall