Microscopy experiment Flashcards
what are the aims of the microscopy experiment?
. to stain cells for examination with a light microscope
. to examine a range of cells and other structures with a microscope to understand their basic structure
Preparing a slide
Animal cell
Step 1
Put a small drop of water onto the middle of a clean microscope slide
Step 2
gently swab the inside of your mouth with a clean cotton bud and then gently rub the cotton swab on the drop of water
Step 3
stain them with methylene blue
Step 4
place a coverslip on top by standing the slip upright on the slide next to the water droplet. Then, carefully tilt and lower it so it covers the specimen. A mounted needle can be used to hold the specimen in place as the coverslip is lowered (try not to get any air bubbles trapped in as they’ll obstruct the view of the specimen)
What does the coverslip do
the coverslip protects the microscope and prevents the slide from drying out when it’s being examined
Preparing the slide
Onion Epidermis cell
Step 1
add a small drop of water to a clean microscope slide
Step 2
use tweezers or forceps to peel some of the epidermal tissue from the skin of an onion. Using the tweezers/forceps place the epidermal tissue in the water on the slide
Step 3
add 2 drops of iodine to stain the cells - this will highlight the structures in the cell by adding colour to them and make sure the onion skin lies flat on the slide and there are no air bubbles trapped
Step 4
place a coverslip on top by standing the slip upright on the slide next to the water droplet. Then, carefully tilt and lower it so it covers the specimen. A mounted needle can be used to hold the specimen in place as the coverslip is lowered (try not to get any air bubbles trapped in as they’ll obstruct the view of the specimen)
Step 5
remove any excess stain by soaking it with paper towels
Using the microscope
Step 1
Place the slip on the stage of the microscope and clip it into place
Step 2
Turn the nosepiece to select the lowest power objective lens (x10)
Step 3
Use the coarse adjustment knob to move the stage up so that the the slide is just below the objective lens (don’t look down the eyepiece whilst doing this)
Step 4
Looking down the eyepiece use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
Step 5
Now use the fine focus knob to further focus the image
Step 6
Repeat the process with higher magnifications for if a greater magnification is required
Step 7
Observe the cells and make a labelled drawing of the cells that you see including any visible sub-cellular structures
Risk assessment
. iodine solution - wear safety goggles when handling it
. care when handling coverslips, microscope slides and mounted needles
. care must be taken when looking down the microscope/eyepiece if the illumination is too bright
What is one way to determine the scale for your drawing using an eyepiece graticule?
1.Clip an eyepiece graticule to the top of the slide and select the ×100 objective lens on the microscope.
2.Line the cells up and count how many fit along 1 mm on the eyepiece graticule.
3.Divide 1 (mm) by the number of cells counted to find the length of one cell and add this to the drawing.
What is another way to determine the scale for your drawing using an eyepiece graticule?
1.Place a stage micrometer on the stage of the microscope.
2.Line up one of the divisions on the eyepiece graticule with a fixed point on the stage micrometer.
3.Count the number of divisions on the eyepiece graticule that correspond with a set measurement on the stage micrometer.
4.Calculate distance in micrometres of one division on eyepiece graticule.
