The Effects of Osmosis and Diffusion
The experimentation of last week’s lab was in order to test the many effects of diffusion and osmosis amongst four experiments. One such experiment was testing the effects of molecular weight on diffusion in relation to the use of Agar. The methods performed included the use of two acids, HCl and acetic acid. Both acids were placed into an Agar-filled dish and, over increments of 15 minutes, data collection was taken based off the diffusion rate and the diameter length of both the HCl and the Acetic Acid. The resulting factor was the HCl exhibited a greater rate of diffusion, directly resulting in a lager diameter. This implies that the HCl ultimately has a smaller molecular weight. The next experiment was based off osmosis of an animal cell; a chicken egg. After submerging two different chicken eggs in distilled water and 10% salt water, once again intervals of 15 minute data collection was taken for a total of one hour. After each interval the weight in grams was taken and then the eggs were placed back into the solution for further analysis. Ultimately, the egg in distilled water exhibited an increase in weight while the egg in salt water was the opposite; a decrease in weight. This conclusion proves that water diffusion occurs from a hypotonic solution to a hypertonic solution. Osmosis in a plant cell was tested by comparing an Elodea cell in pond, distilled, and salt water. After obtaining samples of the Elodea cell and preparing a wet mount of each leaf using all three types of water, observations of the cells in a compound microscope was the next step. From there, comparisons of all three types of solutions in order to determine the apparent differences in osmosis were needed. When examined, the cell in pond water was not as defined; this result implied that water left the hypotonic cytoplasm of the cells causing it to wither in a way. Introduction
In order to conduct the experiments of this lab, a hypothesis is no doubt necessary. In reference to the effects of molecular weight on diffusion a person is lead to believe that since the atomic mass unit of Acetic Acid is greater than that of HCl, the rate of diffusion of Acetic Acid will be slower and therefore produce a smaller diameter. As stated by Watson (2011), “larger molecules diffuse more slowly because of resistance from molecules of the medium.” This “medium” is the means of passing through the spaces in between a molecule. This was as well stated by (Watson 2011). Reiterating what was described, unlike smaller molecules, which can fit through a medium more easily, in turn allowing for a faster and more sufficient means of diffusion, a larger molecule has the resistance from a specific medium, which in a way is pulling back molecules therefore causing a prolonged time of diffusion. This resistance is a direct correlation and explanation as to why the diffusion rate of a relatively larger molecule exhibits a longer rate of diffusion, as with the comparison of hydrochloric acid and acetic acid, and ultimately the purpose of this experiment. Based on the background information acquired on osmosis of an animal cell, it is safe to assume that after each interval of fifteen minutes, the weight of the animal cell in distilled water will continually grow, while the egg in salt water will decrease in weight. Derived from information provided by (Fisher, Williams, & Lineback 2011), an animal cell, which is hypertonic, placed into a hypotonic solution of distilled water will cause water to diffuse into the hypertonic cell, seeing as diffusion occurs from hypotonic to a hypertonic solution. With any type of diffusion process, the particles that are being diffused tend to travel from a concentration that is greater to one that is smaller; moving down in the concentration gradient. This is the direct result of the increase in weight of the animal cell in the experiment. In relation to a chicken egg, the...
Cited: Fisher, K., Williams, K., & Lineback, J. (2011). Osmosis and diffusion conceptual assessment. CBE Life Sciences Education, 10(4), 418-429. doi: 10.1187/cbe.11-04-0038
Watson, C. M. (2011). Diffusion and osmosis. In Biology 1441 Laboratory: Cellular and Molecular Biology (pp. 76-91). Boston: Pearson Learning Solutions.
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