In this lab, your lab group will be observing the effects of solutes on osmosis

Question

In this lab, your lab group will be observing the effects of solutes on osmosis using either skin of a red onion. If using Hydrilla, plants in class come from the San Marcos River where they were introduced for the aquarium trade- but the idea failed and nts prospered. Currently, there is a concerted effort to remove Hydrilla from the waterways an Marcos. The leaves of Hydrilla have cells that are large and contain numerous large chloroplasts. In healthy cell beneath the cell membrane, occurring close to the cell central vacuole in these plan s, cytoplasmic streaming is apparent around the central vacuole just t cells is colorless but its increase and decrease in size can be wall or on the periphery of the cell. The ered by noting the position of the chloroplasts. Red onion epidermal cells contain a central vacuole filled with red pigment. The central vacuole stores water and takes up the vast majority of cell volume (-90%) making the process of osmosis easy to observe. Protocol 1. Red onion epidermis or Hydrilla stored in fresh tap water and in plenty of light will be supplied. 2. If using red onion-peel a small, very thin layer of the skin off with the aid of a scalpel and place on a slide with a drop of water. Cover skin with a cover slip. If using Hydrilla, pick off

Explanation / Answer

4) to draw i would have to look at the slides, as the solutions can have different affect on different cells. But usually in distilled water and 5% Nacl solution, the cells swell up due to osmosis of water into the cells.

As the concentration of NAcl increases or 1M solutions of other solutes are used, water from the vacuoles diffuses out into the solution, leading to shrinkage. All though the cell shrinks, the cell wall being rigid, doest not shrink and hence a gap between cell wall and cell membrane will eb observed.

5) Yes recovery is seen when the cell is placed in distilled water.

we know that the cells of hydrilla have vacuoles that contain water and inorganic and organic compounds. When this cell is placed in distilled water, due to osmosis water will enter the cell and thus recovery from the initially shrinkage occurs.

6) yes there is a relationship between recovery of cell volume and size (rather amount or concentration) of solute molecules.

If the solutions used lower concentrations of solute as the water in the vacuoles, water from solution enter the vacuoles through osmosis and the recovery from shrinkage takes place.

7) yes the hypothesis will be observed in the experiment. if concentration of solution is lower that the solute concentreation of the vacuoles, water enter the cell and it swell. If the concentraton is higher than hte solute concetration of the vacuole, then the cell shrinks.

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