单元结构

Start by placing 2-3 drops of distilled water on a clean microscope slide. Gently scrape the inside of your cheek with a clean toothpick without causing discomfort or bleeding. Mix the collected cheek cells with the water, then add two drops of methylene blue staining solution. Let the mixture sit for 3 minutes at room temperature. Add a drop of glycerol, then carefully place a cover slip over the mixture and blot away excess liquid with blotting paper.

Place a thin strip of onion into distilled water using forceps. Transfer the onion to safranin solution and soak for 30 seconds to stain the cells. Move the onion back into distilled water to rinse. Place 3 drops of glycerol on a microscope slide, transfer the onion onto the glycerol, and carefully place a cover slip over it. Blot away excess liquid with blotting paper to complete the preparation.

Methylene blue is used for animal cheek cells because it effectively highlights cellular structures in animal tissue. Safranin is used for plant onion cells because it penetrates plant cell walls and stains the cell structures distinctly. These different stains are chosen based on the tissue composition and cell wall structure of each cell type, allowing clear visualization of nuclei and other organelles under the microscope.

Total magnification is calculated by multiplying the eyepiece magnification by the objective lens magnification. In this experiment, the eyepiece provides 10X magnification. The objective lenses offer 4X, 10X, and 40X magnification. For example, using the 40X objective lens results in 10X times 40X, which equals 400X total magnification.

Both cell types contain nuclei, which should be labeled in your observations. Plant cells from onion tissue display cell walls that give them a more rectangular shape, while animal cheek cells appear more rounded. Plant cells may show additional structures like chloroplasts or vacuoles, whereas animal cells lack these organelles. Recording these differences helps validate the experimental hypothesis about structural variation between cell types.

Glycerol serves as a mounting medium that preserves cells and maintains their structure on the microscope slide. It prevents cells from drying out during observation and helps keep the cover slip in place. Glycerol also improves the optical clarity of the specimen, allowing for better visualization of cellular structures at different magnification levels during microscopic examination.

The experiment compares onion plant cells and human cheek cells by preparing both types using similar staining and mounting techniques, then observing them under a compound microscope at multiple magnification levels. By examining both cell types side-by-side and recording structural observations, the experiment allows you to identify similarities like nuclei and differences like cell walls, directly testing whether the two cell types differ in overall shape and membrane structure as hypothesized.