Membranes160-page10 - protists are used to collect excess...

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Membrane Structure and Function - 10 Hypertonic Environments An environment which has a higher proportion of solutes than found inside the cell will cause water to leave the cell. Salt water, for example, is hypertonic to the cells of freshwater organisms. A cell placed in this environment will lose water and shrivel, a phenomenon called plasmolysis, unless it has special mechanisms to prevent this. Plasmolysis in Plants Hypotonic Environments An environment that has a lower proportion of solutes than found inside the cell will cause water to enter the cell. Fresh water, for example, is hypotonic to the cells of all organisms. Animal cells may swell to bursting when placed in fresh water. Animal cells, therefore, require some method to prevent this and maintain osmotic balance. One method of doing so is through vacuoles. The contractile vacuoles found in
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Unformatted text preview: protists are used to collect excess water which moves into their cell, and periodically, "spit" the water back out into the environment. Contractile Vacuole in the Paramecium Full Empty Plant cells use osmotic pressure to their advantage, using the cell wall and central plant vacuole. As mentioned earlier, stored substances in the vacuole attract water that increases fluid pressure within the vacuole. This pressure forces the cytoplasm against the plasma membrane and cell wall, helping to keep the cell rigid, maintaining a condition of turgor. Turgor provides support and strength for herbaceous plants and other plant parts lacking secondary cell walls. When plant cells lose turgor, they wilt, a condition known biologically as plasmolysis....
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.

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