Determining the Osmotic Equilibrium of Potatoes
Danielle Soule, Honors Biology, March 18th, 2013
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Abstract: In this lab, our group tried to determine the osmotic equilibrium of potatoes by testing potatoes in solutions of different strengths. We saw that the solutions of lower strengths had swelled the cells of the potatoes and the solutions of higher strengths had decreased the size of the cells of the potatoes. We found that this was due to osmosis. The cells of the lower strength solutions were in a hypotonic solution, and the cells in the higher strength were in a hypertonic solution. We used the information we gathered to conclude the osmotic equilibrium of a potato cell is about 2.7 M.

INTRODUCTION Our biology class was learning about the basics of osmosis and diffusion. Diffusion, being the tendency for molecules of any substance to spread out into available space (Cambell 2002), is directly linked to osmosis which is the diffusion of water across a membrane toward the side that cannot transverse the membrane (Johnson, 2000). Thus, in cells, movement of H20 into and out of a cell is influenced by the relative concentration of solute on either side of the cell membrane (Mahar 2013). We saw the affects of osmosis when we submerged potatoes into solutions of different strengths to see how the cells would react to this change in environment. We saw that some of the cells were in a hypertonic solution, which has a higher solute concentration compared to the cells, and some were in a hypotonic solution, which had a lower solute concentration compared to the cells (Timberlake 1999). The cells in hypertonic solutions were expected to become smaller due to plasmolysis, a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall. The cells in the