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Aim: Drawing cells

1. Peel a one cell layer of skin from an onion (to help see individual cells) using a scalpel and tweezers
2. Place this on a microscope slide, add a drop of iodine solution to stain parts of the cell
3. Place a cover slip on top and put it on the stage (stand the cover slip upright on the slide, then tilt and lower it so no air bubbles are trapped underneath because they obstruct your view)
4. Turn on the light and start with the lowest-powered objective lens
5. Look down the eyepiece and focus with the coarse and fine adjustment knobs, increasing magnification as needed

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Risks

• Care must be taken when looking down the microscope if the light is too bright.
• Iodine solution is an irritant which could cause a skin rash —> Clean up spills immediately
• Care must be taken when handling coverslips and microscope slides (making sure they don’t splinter) </aside>

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How to draw cells

• Include magnification / scale
• use continuous lines
• Do not draw overlapping cells
• Draw all the cells present
• Label cell parts

ELECTRON MICROSCOPES: Higher magnification + higher resolution —> sub-cellular structures can be seen in detail