Onion Cell Experiment

Author's note; This is a PHEOC on the affects of different mixtures on plant cells. 

Problem: What affects will different combinations of substances and blue dye have on the cells of an onion?
Hypothesis: I think that the thicker the substance, the smaller the cell membrane will get. I think this will happen due to previous research on the traveling of water molecules through the membrane. While the water molecules freely float in and out of the cell, the bigger molecules will not be able to enter, staying on the outside of the membrane.


Experimental Design:
Materials:
1. Microscope
2. Slides/slide covers
3. Onion
4. Tweezers
5. Beakers
6. Pipette
7. Water
8. Blue Dye
9. Hydrochloric acid
10. Sugar
11. Cornstarch
12. Baby Powder
13. Baking powder
14. Baking Soda
15. Salt


Variables:
CV: The layer of the onion used, the slides and slide covers used.
IV: The mixtures used on the piece of onion.
DV: The effect of the mixture on the onion.


Procedure:
We will consistently draw the same part of the onion, the epidermis, a layer that is exactly one cell in thickness. We will then place the epidermis on a slide and add around two or three drops of the mixture, and finally place the slide cover on top, attempting to eliminate all air bubbles. The onion will then sit, reacting to the mixture, while at least two more are made with the same mix to produce an accurate observation. We will then collect information about the reactions and provide a conclusion.


Observations:
Following the application of simple combinations such as sugar or salt water, we observed the membrane shrinking into the cell, whereas the cell wall remained the same. With thicker substances with larger molecules we didn't see results we were expecting. Although we could see the nucleus, the cell wall and membrane seemed unchanged.


Conclusion and Analysis:
Kendall and I hypothesized that because of the small size of the sugar and salt molecules, they were allowed to flow freely in and out of the membrane along with the water. We believe the process of diffusion evened the concentrations out, causing the cell to lose water, and shape. The appearance of the nucleus threw us off for awhile until we realized that it was simply the blue dye that had soaked into it, making it visible. We concluded that we did not have a high enough concentration of blue dye in the other mixtures. Although there were several variables that weren't consistent and our overall observation did not provide one conclusion, we did see some things we were expecting to happen to the cell and our previous research helped a lot with the understanding of the experiment.