Proper Microscopic Observation of Animal Cells and Plant Cells under Light
Microscope
Sharlimar Faith Calimutan
Science, Technology, Engineering, and Mathematics Strand – A
Janiuay National Comprehensive High School
Abstract
Observing cells involves refined practice and equipment such as microscopes, and thus, can be a difficult task to
do. Hence, this report aimed to learn and apply the proper methods for operating the optical microscope to observe and
compare animal cells and cheek cells. To acquire this, the student has done laboratory work utilizing a 10x magnification
eyepiece, iodine solution for staining and a light microscope focusing on a low power objective (LPO) lens and a highpower objective (HPO) lens to examine cheek cells and onion cells as representations of animal cells and plant cells,
respectively. Results have found the distinguishing features between cheek cells and onion cells. Under LPO and HPO,
onion cells have prominent cell walls, cytosol, and nucleus, while cheek cells have an irregular shape, cytoplasm, and a
slightly noticeable cell membrane. However, the image of cheek cells did not emphasize the nucleus of the cells under LPO
and HPO. This report suggests that there is a further need to improve the calibration of the microscope to attain a better
view of cheek cells and other cells as well as consider and improve the factors involving the matter.
Keywords: Animal Cells, High Power Objective Lens, Low Power Objective Lens, Magnification, Plant Cells
Introduction
Microscopy involves the technical practice of
viewing samples and objects using microscopes that are
either too small for the unaided eye to perceive or are too
small to be viewed clearly by the human eye (What Is
Microscopy? | The University of Edinburgh, 2018). There
are many types of microscopes but for this activity, light
microscope was used. It is the type of microscopy in
which light is transmitted from a source that is on the
sample's other side from the objective lens. To focus the
light on the sample and attain optimum brightness, it is
typically passed through a condenser. Following the
sample, the light passes via the objective lens, which
enlarges the image of the sample, and then to the oculars,
where the larger picture is viewed. There are two types of
light microscopes based on the nature of the light source:
the simple microscope and compound microscope.
Since it is light microscopes are cheaper than
electron microscopes, it was used in simple scientific
laboratories to improve the scientific knowledge of the
students. Scientific laboratory is essential to the holistic
development of a learner as it involves multiple tasks to
understand complex concepts. Therefore, schools and
governments are encouraged to build scientific
laboratories in their countries to be utilized by students
and improve their scientific innovation.
In the case of the Philippines, there is a further
need to enhance the scientific innovation and skills of the
students given several studies and reports discovering the
lack of scientific knowledge of Filipino students. One
such study is the 2019 edition of the Trends in
International Mathematics and Science Study (TIMSS),
which involves Grade 4 Filipino students (Kelly,
Centurino, Martin, & Mullis, 2020). The study gave the
Philippines scores of 297 and 249 in mathematics and
science, respectively, which is the lowest among the 58
countries involved in the study.
Looking at the situation, Filipino students need to
observe, experiment, and explore concepts like scientists,
and to do that, a scientific laboratory is vital. In addition,
research by American Chemical Society (ACS) has stated
that students who engage in well-designed laboratory
experiences develop problem-solving and criticalthinking skills, as well as gain exposure to reactions,
materials, and equipment in a lab setting. And given this
activity of observing cells, participants will be able to
improve their scientific proficiency and literacy both
individually and interactively.
Thus, this report aimed not only to accurately
calibrate the microscope and apply approaches to
observing cells but also to assess the scientific capability
of the learner in laboratory work.
Materials and Methods
The main purpose of this report is to determine
how to use and adjust the microscope from low power
objective to high power objective during the observation
of animal cells and plant cells. Thus, this activity evolved
from enhancing the skills in proper calibration or focusing
of the cells. Before starting the experiment, preparation of
the specimens and other materials such as laboratory
tools, including the microscope, toothpicks, iodine
solution, glass sides, and droppers, as well as the
cleanliness of the environment has been done.
First, the students proceeded to start with onion
cells by peeling a thin skin of an onion epidermis and
putting it on the center of the glass slide. Next, a small
amount of iodine stain was put on the top of the specimen
using the dropper and waited for about 10 seconds so the
stain could penetrate the cells before a clear glass cover
was put on top and repaired the air bubbles. Then the
specimen was put on the center stage of the microscope
and held tightly using the stage clip. Afterward, the
experimenter adjusted the microscope, starting with LPO,
further calibrating the course adjustment knob and fine
adjustment knob and improving the light to be reflected to
enhance the resolution of the specimen when viewed
under the microscope. Calibration continued for minutes
until the experimenter found a detailed and clear view of
the specimen. After observing under LPO, the student
switched the objective to HPO to magnify the specimen
again. Lastly, the observer documented the specimen for
this report.
Before observing cheek cells, the observer
cleaned the glass slide and glass cover again. Then the
student obtained the cheek cells by gently scraping the
inside of the mouth with the use of a toothpick. And just
like the onion cells, the cheek cells were put on top and in
the center of the glass slide, then stained with iodine
solution before being put underneath the coverslip. With
the same procedure, calibration of the microscope was
done until better images of the cheek cells under LPO and
HPO were achieved.
Figure 1. (a) Onion cells under LPO; (b) Onion cells
under HPO; The arrow designated the parts of the cell.
In the second experiment, as seen in Figure 2,
most of the cheek cells under LPO and HPO do not have
a noticeable nucleus even if the specimen was stained
with iodine solution, but have cell membrane, cytosol, and
shape irregularities. The expected result was to have a
small dark-regioned nucleus and clarity of the image.
Results and Discussion
In the first experiment, onion cells were observed
to have an evident nucleus, cell wall, cell membrane, and
cytoplasm. In Figure 1., the prominent parts of the onion
cells under LPO and HPO have been shown. The
rectangular boundary depicts the cell wall and inside the
cell is the cytoplasm, while the slightly circular opaque
matter on each cell is the nucleus. It can be learned that
iodine solution enhances the resolution of the cells as well
as the nucleus is not clear under LPO but became visible
under HPO.
Figure 2. (a) Cheek cells under LPO; (b) Cheek cells
under HPO
This may have involved interferences such as
improper calibration, contrasting, and illumination errors.
There is too much dust and debris on the surface, as well
as the cells are in low concentration. It can also be
observed that there is resolution, contrasting and focusing
errors that have occurred during the experimentation.
In lieu of the experiment, the errors in the images
were assessed. First, poor contrast can be a usual
indication that the substage condenser aperture diaphragm
is opened too wide, causing flare and considerably
reducing image contrast. This problem plagues all types
of photomicrography, including color, black & white, and
digital. To improve the contrast of the specimen in a light
microscope, adjust both the field diaphragm and the
aperture diaphragm. (Abramowitz & Davidson).
Next, poor resolution of the specimen can be the
result of improper adjustment of the substage condenser
aperture diaphragm. When a microscope is properly
configured for Köhler illumination (the method of
providing the optimum specimen illumination), the
aperture diaphragm should have an iris diameter opening
that lies between 65 and 80 percent of the objective
aperture. Hence, the condenser aperture diaphragm
should be set to a position that will provide a compromise
mixture of direct and deviated light that depends, to a
large degree, on the absorption, diffraction, and refraction
characteristics of the specimen. (Abramowitz &
Davidson).
Meanwhile, contamination of dust can appear as
colored artifacts when using color film, and as black or
gray spots on black and white film just like on the
specimen. If the debris appears in sharp focus, then it is
usually occurring from contamination of a lens surface
residing in a plane conjugate to the focused specimen. The
field lens and any glass (often color balancing or
correcting filters) adjacent to the microscope field
diaphragm are often prone to collecting dirt, and these
components lie near one of the principal image conjugate
planes. Contamination near the field diaphragm will
appear in sharp focus on film, and scratches or dirt on
filters placed near the field diaphragm are often a source
of haze and debris artifacts. Glass surfaces that have been
scratched will appear as unsharp areas on
photomicrographs, as will bubbles embedded in the lamp
condenser glass or in heat-absorbing filters. (Abramowitz
& Davidson).
Another common source of dirt and debris is the
specimen itself, which also resides in a conjugate plane.
Dust adhering to the surface of the coverslip will appear
as unfocused dark spots on the film, while contamination
underneath the coverslip near or mixed with the specimen
will usually appear as debris that is in focus with the
specimen. (Abramowitz & Davidson)
Lastly, the lack of proper focus and/or blurry
images represent one of the most common errors in
photomicrography. The source of these errors is usually the
result of vibration in the microscope stand or improper
adjustment of the focal distance between the optics and the
film plane. Often, the image will appear in sharp focus
through the eyepieces, but resulting photomicrographs are
blurred or unsharp. This is an indication that the film plane
and viewing optics may not be parfocal. (Abramowitz &
Davidson)
Conclusion
The present report discusses the importance of
laboratory work in describing animal cells and plant cells.
The results indicated the parts of the cell in each specimen
under LPO and HPO. However, the parts of the animal
cells were not clearly evident in the experiment. Hence,
several errors in the problem were evaluated and
explained. Factors affecting the image quality of the cells,
such as poor contrast, blurry images, dust and debris, and
poor resolution as a result of improper calibration and
preparation, were described. Therefore, there is a further
need to consider and limit those factors to avoid the
problem when doing experimental work.
Acknowledgment
This work was accomplished with the support of
the General Biology I teacher of Science, Technology,
Engineering, and Mathematics Strand-A (STEM-A)
named Jay Cee Jondonero, the supervisor of the said
strand, who is named Digna Esteva Jolito, as well as the
parents giving the researcher the financial support to buy
the needed materials. Other students have also helped the
researcher by interacting and comparing their own
findings to achieve better results for the experiment.
References
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Troubleshooting microscope configuration and
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Kelly, D.L., Centurino, V.A.S., Martin, M.O., & Mullis,
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