Measurement and observation of cells

In 1673, Anton van Leeuwenhoek built a microscope using lenses and was the first to observe live bacteria and protozoa.

• Cells are very tiny, so we cannot see them with the naked eye. We use microscopes to see them.
• The compound microscope magnifies objects placed on a glass slide, making them much larger.

Units to Measure Cells:

• 1 centimetre (cm) = 10 millimetres (mm)
• 1 millimetre (mm) = 1000 micrometres (µm)
• 1 micrometre (µm) = 1000 nanometres (nm)

1. Aim: To observe the structure of onion cells under a microscope and understand the basic structure of plant cells.

2. Requirements: onion segment, forceps, glass slide and cover slip, water, iodine or eosin solution (stain), and compound microscope.

3. Procedure

• Peel a thin layer from the inside of an onion using forceps.
• Place the layer flat on a glass slide and add a drop of water.
• Add a drop of iodine or eosin (stain) to make the cells clearer.
• Cover it with a cover slip carefully, without bubbles or folds.
• Observe the slide under the microscope using the 10X lens.
• Try the same steps with parts of other plants, like leaves or roots.

4. Conclusion: The experiment shows that plant cells are box-like in shape and contain structures like the cell wall, cytoplasm, and nucleus. This process helps us observe plant cell organisation and compare it with that of other organisms like amoebas and paramecia.

Onion cells are seen under a compound microscope