Investigation 1 dealt with surface area to volume, and why cells are as small as they are. We hypothesized that the 1cm cube would have the highest diffusion rate since it had the highest ratio of surface area to volume. The results supported our hypothesis, and the 1cm cubed was the only one that displayed full penetration. Cells remain small because a higher surface area allows for more cellular activity, and having a high ratio of surface area to volume provides an optimal surface area in a compact space.
In investigation 2, we created models of cells using dialysis bags and filled them with a solution (in our case, 10ml of 1M sucrose), and placed them into a beaker containing another solution (for our group, 100ml of 1M glucose). We weighed the models before placing them in the beakers and then again, after removing them after a 30 minute soak. For us, the cell gained 12.9% more of its' original mass. The underlying concept behind this investigation was tonicity; molecules will diffuse down a gradient until equilibrium is reached. Our cell gained mass, suggesting that molecules flowed into the "cell" from the solution; thus, this suggests that the solution was initially hypotonic.
Investigation 3 involved observing the cells of an onion through a microscope. First, we looked at the cells without placing water on them; then, we exposed the cell to both distilled water and saltwater. The distilled water resulted in water flowing into the cell, as the concentration in the cell was lower. When exposed to saltwater, however, the cell lost water and shriveled, as the concentration of water in the cell was higher than in the saltwater. This exemplifies both the effects of differing tonicities, and the fact that the amount of free water is more important than the total mass. There might have been just as many water molecules in the saltwater, but many of them were unavailable due to being bound to salt molecules, thus resulting in a hypertonic solution.
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