Lab Report - Abstract In order for cells to interact with...

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Abstract In order for cells to interact with their environment, water and other chemicals must be able to move across the cell membrane and across the cell. Movement within the cell occurs by a process known as diffusion. Water molecules move across the cell membrane by a related process known as osmosis which is movement of molecules down a concentration gradient and at the same time across a membrane. Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. Cell membranes do not allow all molecules to cross them. They are said to be "selectively" or "differentially" permeable; only certain molecules can cross the membrane into or out of a cell. This was concluded by the various experiments we’ve done: The onion cells and plasmolysis, diffusion with glucose/starch solution, the osmosis lab with the various molarities of sucrose, and water potential and the potato cells. During the onion cell experiment, we observed the location of the vacuole before and after adding a 15% NaCl solution to the cells. During the Diffusion lab, we studied the movement of Glucose and IKI across a selectively permeable membrane which was modeled by the dialysis tubing. In the Osmosis lab, we used dialysis tubing to investigate the relationship between solute concentration and the movement of water through a selectively permeable membrane. And finally in the last experiment, we used potato cores placed in different molar concentrations of sucrose to determine the water potential of the potato cells. During the onion cell experiment, we observed the location of the vacuole before and after adding a 15% NaCl solution to the cells. The 15% NaCl solution caused the vacuole to plasmolize, or shrink. Not all molecules are small enough to be diffused. During the Diffusion lab, the starch and glucose molecules were small enough to exit the dialysis bag and the IKI was able to enter. The presence of starch was indicated by the dark blue coloring in the dialysis bag after 30mins. The same with the IKI, the presence of the IKI was shown by the yellow color in the cup after 30mins. The phenomenon of osmosis is visible in the movement of water across membranes or barriers resulting in the gain or loss in mass on either side of the barrier. Since the water is moving through the membrane, it would change the mass and volume of the dialysis tubing bags, and this change can be calculated to find the percent change in mass. After calculating the initial and final masses, we knew that osmosis had occurred. During potato cell experiment, we took the initial mass of the potato cores and put the in a cup with 100mL of different molarities of sucrose solutions and let them sit overnight. We also calculated the water potential of the potato cells. Introduction
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This note was uploaded on 02/16/2009 for the course BIO 82478 taught by Professor Johnd.griner during the Spring '08 term at Valdosta State University .

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Lab Report - Abstract In order for cells to interact with...

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