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Effects of Stress on Biological Membrane

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Effects of Stress on Biological Membrane Abstract In this experiment, the spectrometer was used to determine the effects of osmosis, pH, and detergent on biological membrane. Small beet pieces were soaked in various solutions and the intensity of red-pigment emitted was proportional to the damage done. Solutions with a greater concentration of salt caused more damage to the beet membrane due to osmosis. Solutions with an highly acidic and highly basic pH caused the most damage to the cell. Also, pH solutions in the neutral range 6-8, had little or no effect on the cell. Detergent solutions with a small concentration of SDS, 0% to 0.2% caused the most damage. Introduction To maintain order in a cell, the membrane consists of lipids and proteins. In a plant cell, the membrane-bound vacuole, tonoplast, is large and contains water. A beet plant's tonoplast also contains a water-soluble red-pigment, betacyanin, which acts as an indicator. When the beet cells are healthy, the red-pigment remains in its vacuole. However, as the membrane is damaged, it spills out into its surrounding environment. The intensity of the red-pigment is proportional to the amount of damage that was done on the membrane. Osmosis is the movement of water across a semi-permeable membrane from a region of low solute concentration to a region of higher solute concentration. To some extent, salt is essential for most plant growth, however, too much can kill it. ...read more.


After the peak (Figure 3), the amount of damage decreases until the 0.5% solution. The lowest cell damage occurred using the 0.4% solution. Figure 3 Effect of Detergents on Cell Membranes Table 3 Effect of Detergents on Cell Membranes Trial Concentration of SDS (%) Absorbance (470nm) 1 0 0.588 2 0.1 0.503 3 0.2 0.745 4 0.3 0.506 5 0.4 0.461 6 0.5 0.572 Discussion My hypothesis, the most acidic solution will damage the cell membrane the most, was based on my previous knowledge of what acid can do. Acid rain can destroy an entire rainforest, but in this experiment, the acidic solution damaged the cell membrane the least. However, the experimental results did not match the expected results because of errors. The absorbency reading for pH 4 is inaccurate since only 1mL of the solution was used and the spectrometer needs at least 2mL for a correct reading. Also, the absorbency for pH 2 may have been higher if more solution was used and was stirred after every minute. The cell damage was greatest when the solution was most basic, and least damaged when the solution had a pH of 6 or 8. This is expected because a solution with a neutral pH of 7, for example water, has little or no effect on cell membrane. Therefore, you can expect solutions with a pH of 6 or 8 to do a small amount of cell membrane damage. ...read more.


The assumption made for this experiment was when lipids are damaged in beet membrane, a red-pigment will spill out into its surroundings indicating the amount of damage done. Also, it was assumed that detergents are made to make lipids and non-polar molecules soluble in water. These are valid assumptions to make because detergent used to wash clothes allows the non-polar molecules, such as stains or dirt, to come off when washed. To improve the results, the experiment should be carried out more carefully with the appropriate amount of samples. It is important that the beets are rinse before soaking and at least 2 mL of each sample is available. To explore the validity of the assumptions, the experiment can be tested with detergents with a higher concentration. This should show the amount of damaged stabilizing as the SDS concentration increases. The results from this experiment can be applied to life in several ways. When shopping for laundry detergent, you know not to pay more for the detergents that advertises a "stronger formula". In this case, the small detergent concentration will break down dirt and stains just as effective as the higher detergent concentrations. For some gardeners annoyed by pesky snails, a quick way to get rid of them would be to pour salt on them. When the snail's cell detects the high salt concentration on its skin, water will be removed from the snail and will eventually shrivel up and die. ...read more.

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