Osmosis Essay

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OSMOSIS IN POTATO CELLS This lab demonstrated osmosis in cells. Slices of fresh potato were placed in cups of fresh and salt water. The results show that water was able to move through the semipermeable membrane of the potato cells. Lab Report Due 4/12/05 This lab demonstrated osmosis, which is the movement of water through the cell membrane. We used slices of potato as a source of cells. The lab had two parts, one where water moved into the cells, and the other part where water moved out of the cells. It is important to understand that a slice of potato is really a collection of thousands of cells all stacked on one another. Think of the slice as a structure made up many many tiny water balloons stuck to each other. Here is a picture of a very thin sliver of potato from the microscope in class: These are plant cells but they do not have very strong cell walls. You should NOT consider the role of the cell walls when you think about the results of this lab. Situation #1 Water Moves Into The Cells The potato slice is placed into a cup of pure water. There also is some water already inside the cells . The water in the cup is more concentrated than the water in the cells. Water molecules will move from an area of higher concentration to an area of lower concentration. The area of lower concentration is inside the cells so the water will move there. The cell membrane is semi-permeable so the water molecules can get through. The cell will expand as the water flows in. As all the cells expand, the potato slice will expand and become more rigid. Situation #2 Water Moves Out Of The Cells The slice is placed in a cup of very salty water. The water in the cup is a low concentration because the salt forces the water molecules apart from each other. The salt makes the water in the cup a lower concentration than the water in

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