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Introduction to Microscopic Work

HOW DOES IT WORK?                                                                             

The cell is the basic unit of all living things. When cells join together to take on a specialized function within a larger organism, they form a tissue. All organisms are made up of at least one cell.  Large organisms, such as humans, are made up of trillions of cells.  Animal and plant cells share similar characteristics as well as differences. In this lab you will observe these similarities and differences under a microscope. You will be looking at cells from both plants and animals.

Experiment 1: Observing plant cells (Onion).                                 

Time allocation: 45 Min

Students will use a microscope to view cells in a wet suspension. A wet suspension is a sample that is viewed in a liquid medium pressed between the microscope slide and the cover slip, the tissue is still living. This allows us the opportunity to see the cell in a living environment. At first the structure of the tissue will be viewed at 4 x magnification then at 10 x magnification enabling students to view the major structure of the cells.  At 40 x magnification students will be able to note some of the components of individual cells. In this way students are able to compare cells and their differences.

Experiment 2: Observing animal cells (Human cheek swab).            

Time allocation: 45 Min

The cells lining of your mouth is constantly being replaced. The old cells that are ready to slough off can easily be collected. Use a toothpick to scrape cells from the inside of your cheek. Prepare a wet-mound slide be sure to use the methyl-blue stain as well. The methyl-blue stain makes the cell components more visible.


  • Use a sharp HB pencil or 0,5mm clutch pencil with HB lead.
  • Use single, solid, thin continuous lines, when drawing scientific diagrams.
  • No shading or colouring of any parts of a scientific diagram.
  • Make sure that the shape, parts as well as the parts are in relation to each other.
  • Drawings of biological specimens such as cells should have a scale.
  • Draw label lines with a ruler, with pen, from the middle of the structure that must be labelled.
  • No crossing of label lines.
  • Label lines underneath each other.
  • Start labels on the right hand side of diagram, if necessary labels may be placed on the left hand side.
  • All labels horizontal, next to label lines.


Longitudinal – the representation of an object as it would appear if cut by the vertical plane passing through the longest axis of the object.

Cross section – a section made by a plane cutting anything at angles to the longest axis.

Cells under a microscope:


Cells are very small, so to be able to see them we need to use a microscope or look at photographs taken under a microscope. These photographs are called micro-graphs.

Relative size of cells:


The smallest objects we can see with our eyes can be measured in millimeters. What we see under the light microscope is measure in units called micrometers (μ). A micrometer is one thousandth of a millimeter. Structures viewed under an electron microscope are measured in nanometers.

How to determine the actual size of a structure:

We can work out the size of cells or smaller structures from a micro-graph by using the magnification of the microscope when the photo was taken, and the scale line on the micro-graph.

The transmission micro-graph of the mitochondrion, above, was taken at a magnification of 64 000 x.

We can calculate the actual length, from point A to point B of the mitochondrion by using the magnification or using the scale line.

  • The mitochondrion is magnified 64 000 x.
  • Measure the length from A to B using your ruler in millimeter.
  • Now multiply the measure length by 1 000 to convert the length into micrometers
The actual length of the mitochondrion = The measured length in micrometresThe magnification

The scale line shows the length of 1 μ on the photo.

  • Measure the length of the scale line.
  • The measured length represents 1μ.
  • Now measure the length of the mitochondrion in mm.
The actual length =


Measured length (mm)Length of scale line (mm)

How to make a wet mount:

  • Cut a lowercase letter. preferably an ‘e’, from the newspaper
  • Place it onto the center of a clean slide
  • Put a drop of water on the top of the letter using a dropper pipette
  • If too much water is added, the cover slip will “float” creating a water layer that is too thick
  • If too little water is added, the specimen may be crushed or dry out too quickly
  • Place the edge of a cover slip against the water and with a pencil gently lower the cover slip over the letter
  • Placing the cover slip in the manner prevents air bubbles from forming underneath the cover slip.