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How do you conduct the onion peel skin experiment?

9 months ago

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21 Replies

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1030 views

S

Shania Littel


21 Replies

Paula Profile Picture

Verified Sherpa Tutor

The onion peel experiment is a simple practical task by which we can visualise plant tissue structure. The outer layer or skin of the onion is a thin transparent tissue which when removed and visualised under a microscope, allows us to see the basic structure of the plant cell including the cell wall, nucleus, vacuole and chloroplast. The process involves first using tweezers or a toothpick to gently remove a thin layer of skin from the inner layer of a piece of onion. Then place onto a microscope slide with 1-2 drops of distilled water to keep the tissue moist. A chemical stain is usually added at this point to help visualise the otherwise transparent tissue. One drop of iodine will suffice. Then gently cover with a cover slip, making sure no air bubbles collect underneath. The prepared slide can now be placed under a microscope and first visualised under low power, working up to a high-power objective to see the plant cell organelles.

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M
Mariam

Firstly Cut open an onion. Then use forceps to peel a thin layer of epidermis from the inside. Further lay the layer of epidermis on a microscope slide. Then add a drop of iodine solution to the layer. Carefully place a coverslip over the layer.

At last observe it under a microscope to see onion cells.


G
Gary Heayn

Peel skin. Take one layer in the bulb and bend/snap it, then peel the very thin epithelial layer. Cut a small piece and place in a drop of dilute iodine solution on a slide and cover with a cover slip.

Aimee W Profile Picture

Verified Sherpa Tutor

To conduct the experiment looking at the cells in onion skin you will need the following equipment:

A microscope

A microscope slide

Coverslip

Onion

Iodine

Tweezers

Knife

White tile

Goggles


Method:

  1. Put your goggles on and clear your workspace
  2. Set up your microscope and ensure that it is set to the lowest power objective lens\
  3. Place your onion on the white tile and cut a small peice
  4. Using your tweezers peel off a single layer of onion skin. Place this flat onto your microscope slide - It is important that is flat and not folded over
  5. Place 2-3 drops of iodine onto the slide
  6. Gently lower the coverslip over the skin - Avoid air bubbles as this can disrupt the view of the cells
  7. Place the slide onto the stage and turn the adjustment knobs till the image has been brought into focus
  8. Sketch your findings and then you can view the slide using higher power lenses


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S
Sidra Tul Muntaha

Peel off a leaf from half a piece of onion and using the forceps, pull out a piece of transparent onion peel (epidermis) from the leaf. Put the epidermis in the watch glass containing distilled water. Take a few drops of safranin solution in a dropper and transfer this into another watch glass.



A
Ashley Chau

1) Make sure that the onion peel is thinly cut so light can go through it.

2) When placing the onion peel on the glass slide make sure to use a tweezer

3) Place some drops of Iodine for colour stain

4) then place a cover slip on top to make sure the specimen doesn't dry out and avoid air bubbles

Ella D Profile Picture

Verified Sherpa Tutor

This is the method for the GCSE Biology required practical:

  1. Safety first - make sure that you put safety goggles on and tie long hair back. If you have a lab coat, put it on. Make sure you remain standing throughout the practical. Remember, iodine is an irritant and can stain clothing, so be careful when handling it. Also, treat glass with care to prevent breakage.
  2. Gather your equipment. You will need:
  3. Light microscope
  4. Slide
  5. Cover slip
  6. Distilled water
  7. Onion
  8. Tweezers
  9. Iodine
  10. Add a drop of distilled water to the centre of the slide.
  11. Use the tweezers to peel off the epidermis (skin) from underneath a layer of onion, then place it onto the drop of distilled water, making sure that it is as flat as possible.
  12. Add a drop of iodine to the top of the onion epidermis.
  13. Carefully lower the cover slip onto the sample of onion skin, lowering it gradually from one side to the other to make sure no air bubbles get trapped.
  14. Place the prepared slide on the stage of the microscope and ensure that it is centred under the objective lens.
  15. View the sample using the lowest magnification of objective lens first, and adjust the light source to the appropriate brightness before focussing the objective lens using the course focus being careful not to touch the slide with the lens.
  16. Use the fine focus knob to bring the image into clear focus. You may now wish to observe the sample under higher magnifications by increasing the objective lens magnification.
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K
Karolina Jagielka

Peel one layer of the onion skin and place the the skin on a microscope slide. Then, put a drop of iodine on the onion skin and place the slide under a microscope. Set the microscope to the lowest magnification and observe the cell structure. You should be able to see the nucleus of the cell.

A
Amena

1. Use a dropping pipette to put one drop of water onto a microscope slide.

2. Peel off a thin layer of epidermal tissue from the inner surface.

3. Use forceps to put this thin layer on to the drop of water that you have placed on the microscope slide.

4. Put two drops of iodine solution onto the onion tissue.

5. Carefully lower a coverslip onto the slide. Do this by:

• placing one edge of the coverslip on the slide

• use the forceps to lower the other edge onto the slide

6. Put the slide on the microscope stage.

V
Vani. M

Presence of large vacuoles and cell wall confirms that cells of onion peel are plant cells. Take a piece of onion and bend it to remove the transparent membranous structure called onion epidermal peel.

Neil W Profile Picture

Verified Sherpa Tutor

First find an onion and carefully peel one layer of skin (a very thin,) put the skin on a microscope slide, put a drop of iodine or other stain, place the slide under a microscope. set the microscope to the lowest magnification and observe the cell structure where you will see the nucleus of the cell.

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J
Jo Earp

This is a great experiment to view plant cells and practice your specimen staining skills. Firstly, you need to get together your materials:

  • forceps
  • Onion
  • microscope
  • Slide
  • Iodine solution
  • coverslip

Start by taking a small section of onion and peel off a thin layer of skin using forceps. Lie the tissue flat on the slide and add a drop of iodine solution. Slowly place on the coverslip to avoid air bubbles. Place the slide underneath the microscope at the objective lens and slowly work up to a higher objective lens by focusing using the course and fine focus.

I
Iqra Rafique

I would help her by peeling the skin of onion and disected part would be examined by the help of compound microscope

R
Rachel Dooley

When using onion skin to look at the cells under a microscope, the first thing you need to cut a small sample of onion using a scalpel. After this separate, the sections of onion and with tweezers remove a thin layer of onion skin. Place the onion skin onto a microscope slide and place 2 drops of iodine solutions (stain) on the onion skin (this allows you to see the cells). Carefully lower a cover slip on the sample. Place the slide on the base of the microscope and start on the lowest magnification (widest view). Focus until cells are found and then move up to the next objective lens.

Husna V Profile Picture

Verified Sherpa Tutor

In order to conduct the onion peel experiment, you need to be in a lab with the correct equipment such as a light microscope to view the onion cells. Firstly take a sample of an onion cell. This is simply done by peeling a thin layer of onion skin using forceps. Gently place the sample on a glass slide. Add a solution to stain the sample ( this could be iodine solution or methylene blue). This step is done to ensure that the cell can be viewed in detail under the microscope. Carefully place a slip over the sample and gently press the top. Ensure that you do not squish it too much as cells can be destroyed. Place the sample under a light microscope and jot down your observations. As this is a light microscope, the resolution will be lower than that of an electron microscope however, you will be able to view the cell in colour for this specific microscope.

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