Measuring the size of cells

The FIB 10 JGo class under Ms. Carter experimented with plant cells and animal cells. For plant cells, we used onion cells and human cheek cells for animal cells.

The microscopes in the science lab have the magnification power of x10 for the eye piece and between x4, x10 and x40 for the objective lens. The total magnification can be low power (x40), medium power (x100), or high power (x400). We photographed the cells using our mobile phones.

We first experimented with onion cells (top image). We took a very thin layer of the inner surface of an onion, then we put it on a slide, added a drop of water, and lowered down the cover slip. We looked at the cells under low power and medium power.

With the cheek cells (bottom image), we made use of methylene blue stain instead of water because cheek cells are transparent, so we used methylene blue to make it more obvious. First, we put a drop of methylene blue on the center of the slide. Then we wiped the lining of our cheek with a plastic coffee stirrer and then smeared it on the drop of methylene blue. We looked at the cells with medium and high power, because the cells are much smaller compared to the onion cells.

In order to measure the cell length, we have to know the diameter of field of view of the microscope. So, we measured a ruler under a microscope. The diameter of field of view in: low power=4.2mm, medium power=1.6mm, high power=0.6mm.

In the onion cells picture, the magnification is medium, and there are 9 cells in the diameter of the field of view. Therefore the actual size of an onion cell is 0.47mm.

In the cheek cells picture, the magnification is high, but it’s not clear how many cells there are in the diameter of the field of view. So, we printed the photo and measured the length of a cell in the photo. The diameter of the field of view in the photo is 12.1cm and the length of a cell is 1.35cm. Hence, the actual size of a cheek cell is 0.07mm .

Petrus Bosa Layarda