Onion Skin Epidermal Cells: How to Prepare a Wet Mount Microscope Slide
Summary
TLDRThis educational video demonstrates the process of preparing a wet mount slide of stained onion epidermal cells. The presenter explains how to select and peel the thin, transparent layer of cells from an onion bulb, transfer it onto a microscope slide, and apply iodine for staining. The video also covers techniques for placing a cover slip to minimize air bubbles and adjusting the microscope's light levels for optimal viewing. Finally, the presenter shows the cells magnified under different objective lenses, highlighting the cell walls, nuclei, and the importance of staining for visibility.
Takeaways
- 🔬 The video demonstrates how to prepare a wet mount slide of stained onion epidermal cells.
- 🧐 The process begins with selecting a smooth and shiny layer of onion bulb for obtaining the specimen.
- 🔎 A thin, transparent layer of cells is peeled off the onion layer using tweezers for use as the specimen.
- 📍 An alternate technique mentioned is peeling the onion skin directly onto the slide for a larger, flatter specimen.
- 💧 Iodine is used as the wet mount solution, which also serves to stain the cells for better visibility.
- 🏷️ A cover slip is applied by holding it at a right angle and allowing it to drop onto the slide, minimizing air bubbles.
- 🔭 The specimen is first examined under a 4X objective lens, magnifying the cells 40 times actual size.
- 🔍 The video explains that a compound microscope is parfocal, allowing for easy transition between different magnification levels.
- 🌑 Adjusting the light level by using the dimmer dial or iris diaphragm can improve contrast and visibility of the specimen.
- 🔬 The final examination is done under a high dry lens at 400 times actual size, revealing detailed cell structures.
Q & A
What is the purpose of the video?
-The purpose of the video is to demonstrate the process of preparing a wet mount slide of stained onion epidermal cells.
What type of specimen is used in the video for the wet mount slide?
-The specimen used is a thin, transparent layer of onion epidermal cells obtained from the inner layer of an onion bulb.
How does one identify the correct layer of onion epidermal cells?
-The correct layer is identified by its smooth and shiny appearance compared to the rough and matte side of the onion layer.
What technique is shown for obtaining the onion epidermal cells?
-The technique involves breaking the onion layer towards the shiny side and gently peeling apart the two pieces to obtain the thin layer of cells.
How should one handle the thin layer of onion epidermis to place it on the slide?
-The thin layer should be torn off with tweezers and then carefully spread out on the slide to avoid it folding over on itself.
What alternative method is suggested for transferring the onion skin to the slide?
-The alternative method is to peel the layer of onion skin directly onto the slide, allowing it to wrap around the slide like Saran Wrap.
What staining agent is used in the video for the wet mount?
-Iodine is used as the staining agent, which provides both the wet component and stains the cells for better visibility.
How is a cover slip applied to the specimen on the slide?
-The cover slip is held at a right angle to the slide and then dropped, allowing it to fall and push the air out, creating fewer air bubbles.
What magnification is used to initially examine the onion epidermal cells?
-The initial examination uses a 4X objective lens, magnifying the specimen 40 times actual size.
How can the contrast of the specimen be improved if the stain is not taken up well?
-The contrast can be improved by adjusting the light level, either by using the dimmer dial on the microscope base or by opening or closing the iris diaphragm.
What is the highest magnification used in the video to view the onion epidermal cells?
-The highest magnification used is with the high dry power objective lens, which magnifies the specimen 400 times actual size.
Outlines
🔬 Preparing a Wet Mount Slide of Onion Epidermal Cells
This paragraph describes the process of preparing a wet mount slide of stained onion epidermal cells. The presenter starts by selecting a microscope slide and obtaining a specimen from the onion bulb. The bulb has a rough matte side and a smooth shiny side, and the goal is to peel off the thin transparent layer of cells from the shiny side. The presenter uses tweezers to tear off a piece of the onion epidermis and places it on the slide. The delicate layer of cells may fold over, so it needs to be spread out. The presenter also mentions an alternative technique for transferring the onion skin directly onto the slide. For staining, iodine is used, which serves as both the wet mount and staining agent. A cover slip is applied by holding it at a right angle and letting it drop onto the slide to minimize air bubbles. The specimen is then examined under a 4X objective lens, which magnifies the cells 40 times. The cells are described as misshapen bricks, and the video shows a microscopic view of the onion epidermal cells.
📸 Enhancing Microscopic Image Contrast and Viewing Techniques
In this paragraph, the focus is on enhancing the contrast of the specimen when viewing under a microscope and adjusting light levels to improve visibility. The presenter demonstrates how to adjust the light by using the dimmer dial on the microscope base or by opening and closing the iris diaphragm, which controls the amount of light shining through the specimen. After focusing the specimen at low power, the presenter switches to a high dry power lens, which magnifies the specimen 400 times. The video shows examples of onion epidermal cells viewed at this higher magnification, where the cell walls and nuclei are more clearly visible. The presenter also suggests visiting Science Prof Online for more educational content.
Mindmap
Keywords
💡Wet Mount Slide
💡Onion Epidermal Cells
💡Microscope Slide
💡Iodine
💡Cover Slip
💡Objective Lens
💡Magnification
💡Compound Microscope
💡Parfocal
💡Light Adjustment
💡Cell Wall
Highlights
Introduction to preparing a wet mount slide of stained onion epidermal cells.
Selection of a microscope slide for the specimen preparation.
Obtaining a specimen from the smooth, shiny side of an onion bulb layer.
Technique to gently peel apart the onion layer to access the epidermal cells.
Method to tear off a thin layer of onion epidermis using tweezers.
Spreading the delicate onion epidermis layer on the slide.
Alternate technique for transferring onion skin directly onto the slide.
Use of iodine as a staining agent for the wet mount.
Procedure for applying a cover slip to the specimen to avoid air bubbles.
Examination of the specimen under a 4X objective lens for initial magnification.
Description of onion epidermal cells appearing like misshapen bricks under the microscope.
Explanation of the compound microscope's parfocal property for ease of focus adjustment.
Observation of onion epidermal cells at 100x magnification for a closer look.
Technique to improve contrast by adjusting light levels for better visibility.
Demonstration of using the dimmer dial and iris diaphragm to control light.
Switching to high dry power for 400x magnification to observe cell details.
Observation of thick cell walls and cell nuclei in the onion epidermal cells at high magnification.
Promotion of additional educational resources available at Science Prof online.
Transcripts
in this video I'm going to show you how
to prepare a wet Mount slide of stained
onion epidermal
cells here's my microscope slide I want
to have that out and
ready I can obtain my specimen from one
layer of onion bulb if I look at this
layer one side is kind of rough and
matte and the other side is smooth
smooth and
shiny I need to break my onion layer
towards this shiny side and then very
gently
peel the two pieces apart there's a thin
transparent layer of cells holding these
two pieces of the onion layer together
that's the layer of epidermal cells that
I'm looking for for my
specimen now I need to obtain a piece of
that onion epidermis to place on my
slide I can do that by tearing it off
with a pair of
tweezers this is a very delicate thin
layer of ss and they'll fold over on
themselves uh so when you place that
onto the slide once you get it off your
tweezers you're going to need to spread
it out a little bit the little piece of
onion epidermis can easily get all
watted up and that makes it very
difficult to see this
sounds while filming in the lab I forgot
to include an easier alternate technique
for getting that onion skin onto the
slide so I'm going to show it to you
here in my dining room with my two
helpers the best way to get a large flat
sheet of these onion epidermal cells is
to peel that layer of onion skin off
directly onto the slide it's very thin
it'll wrap right around the slide just
like Saran
Wrap so apparently I've lost my helpers
because onions are way too stinky so we
might as well head back to the lab
for this wet Mount I'm just going to use
iodine this will provide the wet part of
the wet Mount and it will also stain the
cells and make them easier to
see now I'm going to obtain a cover slip
a clear square that I'm going going to
place on top of my specimen on the
slide the best way to apply that cover
slip is to hold it at a right angle to
the slide at one side of your specimen
and then let it drop let it fall as it
falls it will push the air out and
you'll have fewer air bubbles this way
here's my finished prepared specimen
here's a closer look at the application
of that cover slip again I hold it at a
right angle to the slide I let it drop
that pushes the air out sometimes I'll
give it a little tap and now I'm all
set I'm now going to examine my specimen
using the 4X objective lens that will
magnify the specimen 40 times actual
size here's my first look
microscopically at the onion epidermal
cells magnified 40 times these cells
look kind of like misshapen bricks a
whole bunch of
them the compound microscope is par
focal what that means is once I get my
specimen in focus at one power in this
case the scanning power I can switch to
the next higher objective the low power
in this case and my specimen will still
pretty much be in Focus I'll only have
to adjust the focus a little bit to get
it
crisp here are my onion epidermal cells
magnified 100 times actual
size so this is a closer look at that
specimen we just looked at under 40
total magnification the specimen that
did not stain so
well we stained the specimen to increase
the contrast to make it more visible and
since the stain wasn't taken up that
well there are other ways to improve the
contrast of our specimen when viewing
this specimen and taking this picture I
adjusted the light level I turned it way
down and that helped me see the cells
much more distinctly and
clearly here's just a reminder of the
different ways you can adjust the light
level shining up through your
specimen the first way is to use the
dimmer dial on the base of your scope
that dial will make the light shining up
from the base brighter or
dimmer you can also adjust the amount of
light shining up through your specimen
by opening or closing the iris diaphragm
that's directly beneath the stage it
looks and feels like a camera lens you
twist it and you can let more or less
light through the
stage once the specimen is clearly in
focus at low power that yellow banded
lens I can switch the objective to the
high dry power that's the blue banded
lens and it will magnify my specimen a
total of 400 times actual size here are
a couple examples of onion epidermal
cells viewed at 400 times actual size
through that high dry lens these samples
have stained a little better than the
ones I showed you previously I can see
the thick cell walls and these elongated
cells in this picture I can see a cell
nucleus in the second cell below the
pointer more seriously nerdy amazing
free stuff at science Prof online.com go
there
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