Investigating Osmosis In A Potato

Investigating Osmosis In A Potato

Introduction: "Osmosis is typically defines as the flow of one

constituent of a solution through a membrane while the other

constituents are blocked and unable to pass through the membrane.

Experimentation is necessary to determine which membranes permit

selective flow, or osmosis, because not all membranes act in this way.

Many membranes allow all or none of the constituents of a solution to

pass through; only a few allow a selective flow. In a classic

demonstration of osmosis, a vertical tube containing a solution of

sugar, with its lower end closed off by a semi-permeable membrane, is

placed in a container of water. As the water passes through the

membrane into the tube, the level of sugar solution in the tube

visibly rises. A semi-permeable membrane that may be used for such a

demonstration is the membrane found just inside the shell of an egg,

that is, the film that keeps the white of the egg from direct contact

with the shell. In this demonstration, the water moves in both

directions through the membrane; the flow is greater from the vessel

of pure water, however, because the concentration of water is greater

there, that is, fewer dissolved substances exist in this solution than

in the sugar solution. The level of liquid in the tube of sugar

solution will eventually rise until the flow of water from the tube of

sugar solution, under the influence of hydrostatic pressure, equals

the flow of water into the tube."

-From Encarta 2001

In osmosis, a solvent (often water) moves from a region of low

concentration to a region of high concentration through a

semi-permeable membrane. Here, water molecules diffuse into the

concentrated sugar solution because the water molecules are small

enough to move through the membrane. The larger sugar molecules are

unable to move through the membrane into the water solution. Osmosis

will stop when the two solutions reach equal concentrations on either

side of the membrane[IMAGE]

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In the investigation I will be doing, it is osmosis in plant cells