Onion Peel Under the Microscope | How to Prepare Stained Temporary Mount of Onion Peel

Summary

This educational video guides viewers through the process of preparing and observing onion epidermal cells under a microscope. It details the necessary equipment, the staining process with methylene blue, and the creation of a slide to prevent cell dehydration. The video demonstrates the use of both low and high magnification to reveal the distinct boundaries, rectangular shape, and nucleus location of plant cells, offering insights into basic cellular structures and their functions.

Takeaways

• 🧐 The video demonstrates the process of preparing and observing onion cells under a compound microscope.
• 🔍 The necessary tools for the demonstration include glass slides, cover slips, a needle, a scalpel, forceps, scissors, onions, glycerin, and a staining agent like methylene blue.
• 🧑‍🍳 The presenter peels an onion and carefully removes the inner epidermal layer to use as a specimen for staining.
• 🎨 Methylene blue is used to stain the onion cells, which helps in observing the cell structure more clearly under the microscope.
• ⏳ The staining process should be quick to prevent the cells from drying out, and the stained specimen is placed on a slide with glycerin to keep it moist.
• 🔬 The use of a coverslip is crucial to protect the specimen and to avoid air bubbles that could distort the view under the microscope.
• 🔬 The presenter uses both low (10x) and high (45x) magnification to observe the onion cells, highlighting the differences in the number of cells visible at each magnification level.
• 📐 The cells observed are expected to be nucleated, have a distinct boundary due to the cell wall, and be rectangular or brick-like in shape.
• 🔵 The cytoplasm of the cells is stained light blue, while the nucleus takes up a darker shade of blue, indicating successful staining.
• 🔍 Higher magnification allows for a closer look at the nucleus and cytoplasm, but cell organelles are not visible without an electron microscope.
• 📚 The video concludes with an invitation to subscribe to the channel and visit the website for more educational content on various subjects.

Q & A

What is the main subject of the video?

The main subject of the video is the preparation and observation of onion peel cells under a compound microscope.

What materials are needed to prepare a slide of onion peel?

The materials needed include clean glass slides, cover slips, a needle, a scalpel, forceps, a pair of scissors, onions, glycerin, and a staining agent like methylene blue.

Why is glycerin used on the slide before placing the specimen?

Glycerin is used to keep the specimen moist and prevent it from drying out while being observed under the microscope.

How does one remove the inner lining of the onion peel?

The inner lining of the onion peel is removed by breaking the fleshy leaf into small portions and teasing out the epidermal layer using forceps or a scalpel.

What is the purpose of staining the onion peel specimen?

Staining the onion peel specimen enhances the visibility of cellular structures, such as the nucleus and cytoplasm, under the microscope.

Why is it important to avoid air bubbles under the coverslip?

Air bubbles can interfere with the clarity of the microscopic image, making it difficult to observe the specimen's details.

What technique is used to place the coverslip without trapping air bubbles?

The technique involves touching the edge of the coverslip to the slide, balancing it with a needle, and slowly removing the needle to allow the coverslip to settle without air bubbles.

What magnifications are used to observe the onion peel cells in the video?

The video uses both 10x magnification (low power) and 45x magnification (high power) to observe the onion peel cells.

What are the characteristics of the onion peel cells observed under the microscope?

The onion peel cells are observed to have a distinct boundary, a nucleus located towards the periphery, and are rectangular in shape with closely packed cytoplasm.

Why can't cell organelles be seen with the compound microscope used in the video?

Cell organelles require a much higher magnification than what a compound microscope can provide; an electron microscope would be needed for such detailed observation.

Where can viewers find more courses like the one presented in the video?

Viewers can find more courses on physics, chemistry, biology, mathematics, and computer coding by subscribing to the channel and visiting the website www.manojacademy.com.

Outlines

00:00

🔬 Preparing and Observing Onion Epidermal Cells

In this segment, the video script details the process of preparing a slide of onion peel cells for microscopic observation. The narrator guides the audience through the necessary materials, including glass slides, cover slips, a scalpel, forceps, onions, glycerin, and a staining agent like methylene blue. The process involves cutting the onion, peeling off the outer layer, teasing out the epidermal layer, staining it, and placing it on a slide with glycerin to prevent drying. A coverslip is carefully applied to avoid air bubbles, ensuring clear visibility under the microscope.

05:01

🌿 Analyzing Plant Cells Under the Microscope

This paragraph describes the observation of onion epidermal cells using a compound microscope. The narrator starts with a low power objective to get an overview of the cells, noting their distinct boundaries, rectangular shape, and closely packed arrangement, which is typical for plant epidermal cells. The cells' nucleus is stained dark blue and is located at the periphery, while the cytoplasm appears light blue. Switching to a high power objective reveals fewer cells due to the reduced field of view but provides a more detailed view of the nucleus and cytoplasm. The narrator mentions that to observe cell organelles, an electron microscope would be required. The video concludes with an invitation to subscribe to the channel and visit the academy's website for more courses.

Keywords

💡Onion

An onion is a bulbous plant species in the genus Allium, known for its distinctive taste and pungent smell. In the video, onions are used as a subject for a biological experiment, specifically to observe the cells of an onion peel under a microscope.

💡Compound Microscope

A compound microscope is an optical instrument that uses multiple lenses to magnify images. It is essential in the video for observing the onion peel cells at high magnification, allowing for the detailed examination of the epidermal layer of the onion.

💡Epidermal Layer

The epidermal layer refers to the outermost layer of cells in a plant, which serves as a protective barrier. In the video, the presenter carefully separates this layer from the onion to prepare it for microscopic examination, highlighting its importance in plant structure.

💡Dissection Box

A dissection box is a kit containing various tools used for biological dissection and observation. The video mentions the use of a dissection box, which includes items like glass slides, cover slips, and forceps, all of which are necessary for preparing the onion peel specimen.

💡Glycerin

Glycerin is a simple polyol compound commonly used as a solvent, sweetener, and moisturizer. In the context of the video, glycerin is used to keep the onion peel specimen moist during observation under the microscope, preventing the cells from drying out.

💡Methylene Blue Stain

Methylene blue is a dye used as a biological stain to color cellular structures. In the video, it is used to stain the onion peel cells, making the nucleus and cytoplasm visible under the microscope, which aids in the identification and observation of cellular features.

💡Coverslip

A coverslip is a small, thin piece of glass used to cover a specimen on a microscope slide. The video describes the careful placement of a coverslip over the stained onion peel to protect the specimen and ensure clear viewing without air bubbles, which could distort the image.

💡Air Bubbles

Air bubbles are pockets of air that can form between the slide and the coverslip, which can interfere with the clarity of the image when viewing under a microscope. The video emphasizes the importance of avoiding air bubbles when preparing the slide to ensure a clear view of the onion peel cells.

💡Nucleus

The nucleus is a membrane-bound organelle found in eukaryotic cells that contains the genetic material. In the video, the nucleus of the onion peel cells is described as a distinct, dark blue dot, indicating its presence and importance in the cell's structure.

💡Cytoplasm

Cytoplasm is the jelly-like substance within a cell, which contains many of the cell's organelles. The video mentions that the cytoplasm of the onion peel cells is stained light blue, distinguishing it from the nucleus and highlighting its role in cellular functions.

💡Cell Wall

A cell wall is a rigid layer surrounding some cells that provides structural support and protection. The video script notes that the onion peel cells have a distinct boundary, which is indicative of the presence of a cell wall, a key feature of plant cells.

Highlights

Introduction to observing onion cells under a compound microscope.

List of materials required for preparing an onion peel slide.

Process of cutting an onion in half and peeling out a fleshy leaf.

Kneading the inner lining of the onion peel to obtain the epidermal layer.

Use of methylene blue stain to color the slide for better observation.

Importance of working quickly to prevent cells from drying out.

Application of glycerin to keep the specimen moist during observation.

Technique for placing the specimen on the slide without rolling.

Method to avoid air bubbles when placing the coverslip.

Preparation of the specimen slide ready for microscope observation.

Use of a compound microscope with different magnifications.

Expectation of observing nucleated, rectangular, closely packed epidermal cells.

Characteristic features of onion peel cells under low power magnification.

Observation of the nucleus and cytoplasm staining under high power magnification.

Limitation of microscope magnification for observing cell organelles.

Conclusion of the virtual practical class and invitation to subscribe for more.

Promotion of Manoj Academy's courses in various subjects.

Transcripts

i'm sure you have all seen and eaten an

onion but have you ever wondered what

the cells of an onion look like

in this video we are going to do exactly

that

we are going to prepare a slide of an

onion peel and observe it under a

compound microscope

for that these are the following things

that you would require from your

dissection box

we will require clean glass lights cover

slips

needle

a scalpel

forceps

a pair of scissors

onions

a little bit of glycerine and

i am using methylene blue stain to stain

the slide you may use safranin or any

other stain that is available now let us

start with the work

so first of all i have taken an onion

and cut it into halves

and then i will have to peel out one of

the fleshy leaves of onion

so you see i will just take out the

leaves in such a manner that i get rid

of

this dry

scaly leaf which is present

outside

and i only have this fleshy part that i

need

now after this we are going to

knead the inner lining of this fleshy

leaf

which is actually an epidermal layer

how will i take it out

so i break this

in a small

into a small portion

and then

with the help of a pair of forceps

i will just tease the inner lining of

the onion peel with the forceps or you

can here use a scalpel

but a forceps is always very convenient

you just have to tease it and you will

see the inner lining is coming out

like

a thin strip

all right so this is the layer of

epidermis that we require

however we do not require so much so

what we will do is

we will quickly and everything has to be

done very quickly because you do not

want the cells to dry up so very quickly

i will take a small piece

of this

peel

and this much is enough in fact this is

more than enough

i will put this in the methylene blue

stain that i have taken

on a watch glass

so now you can see

that the specimen is inside the stain

and depending on the strength of the

stain you might have to keep it for a

couple of minutes to five minutes

after this we will take a clean glass

light

we will take the stained

specimen

once it has been stained you can take it

and we will have to place it on the

glass light but before that

we will use a little bit of glycerin and

put it on the slide

why are we using glycerin we are using

glycerin because we do not want the

specimen to dry out while we are

observing it under the microscope the

glycerin will keep the specimen moist

okay now

we will take

the specimen out of the stain

place it on the slide

make sure that this

section that you have taken does not

roll so if you find that it is rolling

anywhere you can simply hold it with

your forceps and tease it with the

needles so that it is straight and it is

laid out on the slide

to make sure that this specimen does not

dry out we will have to cover it with a

coverslip

now this is a coverslip here i am using

a square coverslip you can use a round

cover slip if you have one but while we

put down the coverslip we have to be

very sure that there is no air bubble

trapped inside because if there is air

bubble inside then it will not be

clearly visible the specimen will not be

clearly visible under the microscope so

there is a certain technique for laying

down the coverslip such that you do not

have air bubbles inside let me show you

how

so we will just touch the coverslip

onto the slide

and

balance it

support it with the needle

and we will slowly take the needle out

very slowly

and you will see that there is no air

bubble left

now under this coverslip now we have the

specimen ready so now what do we have to

do

we will have to simply put the spec

slide under the microscope and observe

it so here i am using a compound

microscope we have already seen the

parts of a compound microscope first i

will be using a 10x magnification which

is low power and then i will be using a

45x magnification which is high power to

observe the cells

what kind of cells do you expect to see

in the onion peel

since these are epidermal cells and

these are plant cells we expect to see

nucleated cells we expect to to see

cells which have a very strong boundary

or a very distinct boundary and usually

the epidermal cells are rectangular in

shape so let us see how the cells will

look like and then we can

write down the characteristic features

so now i will just focus the microscope

i am using the 10x magnification i will

focus the slide

so here we can see the cells in low

power as you can see we have

seen that these cells have a distinct

boundary because these are plant cells

so they have a cell wall

they are living cells so you can see a

clear blue dot inside which is the

nucleus and what is the location of the

nucleus the nucleus is located towards

the periphery of the cell

you also see that these cells are

rectangular in shape brick like and are

absolutely closely packed because you

want an epidermal layer to be closely

packed there should be no gap so that it

can provide enough protection

the cytoplasm has been stained light

blue whereas the nucleus has taken up a

dark blue stain

let us bring this under high power and

see if we can magnify the nucleus and

the cytoplasm a little further

so you see under high power you see less

number of cells why because when you are

magnifying the tissue in a microscopic

field

in low power you see a large area and

therefore you can see a larger number of

cells

the moment you use a higher

magnification you see a smaller area of

the specimen

although the image is magnified you see

lesser number of cells

but the nucleus is prominent here so is

the cytoplasm

we cannot see the cell organelles

because for that we need a much higher

magnification which is possible with the

help of an electron microscope

so that was all for today's class i'm

sure you enjoyed it we will be back with

more such virtual practical classes from

manoj academy thank you and see you soon

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www.manojacademy.com

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