Essay on Osmosis in Onion Cell

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The aim of the sixteenth of November experiments was to observe how three different solutions with various sucrose concentration influenced osmosis in relation to three onion cells and the impact on the cells structure. A small square of a red onion skin (membrane) was observed under a microscope at high power (X40) magnification. The observation showed a large number of onion cells. The structure of one onion cell had a general rectangular shape with a developed cell wall, which gives the rectangular shape to the cell and a cell membrane just beneath it.

The observation under the microscope of a cell of an onion skin soaked for 15 minutes in distilled water showed that the cell membrane was pressed against the cell wall. The cell
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The lost of water from the vacuoles and cytoplasm pulled the cell membrane away from the cell wall. The water was diffused from a hypotonic solution to a hypertonic solution. Because the water flowed out of the cell by osmosis, the cell became more flaccid and then plasmolysed.

The observation under the microscope of a cell of an onion skin soaked for 15 minutes in a 0.5 molar sucrose solution showed a cell membrane just beneath the cell wall. The cell wall had a rectangular shape. See diagram 3 for sketch. The cell and its surrounding were in an isotonic solution. The two solutions in the cell and out (0.5 molar sucrose solution) of the cell were homogenous. No net movement of water and change in the cell structure was observed. The components of the solute and solvent were evenly intermixed. The concentration of solute and solvent on either side of the cell membrane was equalized. Because the onion tissue didn’t get any water the cell was flaccid and nonturgid.

Those three experiments showed that the way onion cells are dealing with the movement of water in and out of the cell is by osmosis. That Osmosis is the diffusion of water across a membrane into a solution having a greater solute concentration. The cell
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