Unit 1: fundamentals of science.
An investigation of an onion cell using a light microscope.
The aim of this investigation is to identify the cells within an onion skin using a light microscope. An onion cell is a plant cell which through the light microscope, it should outline the cell wall, cell membrane and the nucleus. Introduction:
Plant cells have a cell wall and cell membrane which animal cells do not have. The cell wall provides support and is relatively rigid, which consists of many long, straight cellulose molecules. However, the cell membrane is a very thin structure around the individual cell. Light microscopes use light as a source of radiation. They also use light rays which have a long 2 objects if they are 0.2 micrometers or further apart. When using the light microscope, the light rays are passed through the specimen which different parts absorb wavelengths of light, this results in different shades of parts of the specimen.
* Safety goggles
* Lab coat
* Light microscope
* Slice of onion
* Distilled water
* Watch glass
* Glass slide (x2)
* Mounted needle
Health and safety:
Wearing a lab coat protects individuals from iodine staining the clothes. Wearing safety goggles protects eyes from when using the scalpel to cut the onion. Be careful whilst moving around the classroom in case of an accident for example falling over bags and disturbing a group of individuals which results in iodine spilling over onto the floor or even skin. Method:
Remove a thin layer of the onion by using fingers or a pair of forceps. Using the scalpel, cut the onion into about 5mm² and only one small piece is needed. Place the piece of onion onto a watch glass and add a few drops of iodine. Wait for 3 minutes remove the piece using forceps and put it onto the glass slide. Add two drops of distilled water onto the onion. Ensure the thin layer is flat and...
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