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To find out the concentration of cell sap within the vacuole of a potato cell.

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Introduction

Biology coursework Osmosis investigation: to find out the concentration of cell sap within the vacuole of a potato cell. Planning Background info: Osmosis Definition Osmosis is the net movement of water from a dilute to a strong solution via a partially permeable membrane against the concentration gradient until equilibrium is reached. Movement is due to water having kinetic energy. The water moves into the vacuole as which is the part that contains cell sap (a salty/sugary solution). When the cell takes in water the vacuole increases in size, which pushes the cytoplasm into the cell membrane, which in turn pushes, the cell membrane into the cell wall. Partially permeable membrane: Each cell is surrounded by a cell membrane. It separates the contents of the cell from the outside. The cell membrane has tiny holes in it. This allows small molecules to pass through but not the large ones. The cell membrane is partially permeable-Osmosis is a special kind of diffusion involving water molecules. It occurs when a partially permeable membrane separates two solutions. Turgidity Osmosis causes plants to swell up if they're surrounded by weak solution and they become turgid. ...read more.

Middle

After the experiment was finished it was then repeated twice more giving me 3 sets of results. The results were averaged and then a graph was formed from that. For a controlled experiment the things I kept the same were: A) Temperature All results were collected at room temperature (20-22 degrees Celsius). I kept the experiment at room temperature by doing all of my results on the same bench in the biology lab. B) Volume of salt solution I used a volume of 25ml of salt solution for every result I assured this by using a measuring cylinder for every volume of salt solution. For safety I always held the scalpel away from myself and used a cutting tile so I didn't pierce the bench. I also acted sensibly with all my equipment for the experiment and never behaved irresponsible or irrational in any way. Evaluation Overall I think my measurements were fairly accurate but could be improved if I did the experiment again. In pouring the different concentrations of salt solution I used a measuring cylinder which was accurate to + or - 1 ml. ...read more.

Conclusion

At 0.5 molar the chips went down by 0.7 grams but when I repeated this, as the data was anomalous the chips lost 0.5 grams in weight. This was because the concentration of cell sap in the potato chip was less than in the salt solution causing the chip to lose water by osmosis therefore losing weight. At 1 molar the chips lost 0.8 grams because the concentration of cell sap in the potato chip was less than in the salt solution causing the chip to lose water by osmosis therefore losing considerable weight. At 2 molar the chips lost 0.9 grams because the concentration of cell sap in the potato chip was less than in the salt solution causing it to lose a lot of weight. It became plasmolysed via osmosis removing enough water from the cells to shrink the vacuoles to their point of no return (when they cannot recover) or further. The weight of the chip at this point was at its minimum for the chip under these conditions. . Conclusion In my experiment equilibrium was reached using a solution of 0.1 moles indicated from my graph and from the table of my results. Therefore as I have evaluated everything thoroughly I agree with this. Equilibrium is reached at 0.1 molar. ...read more.

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