University of Arkansas System
Type of paper: Thesis/Dissertation Chapter
Osmosis and Potato Chips
Osmosis is the movement of water from an area of high concentration to an area of low concentration across a semi permeable membrane. An osmotic system is established when a semi-permeable membrane is placed between two solutions. In this biological systems context, osmosis is the exchange of water between the potato cell and the surrounding medium of varying sucrose concentrated solutions, with the plasma membrane being the semi- permeable membrane. Because water molecules have kinetic energy, they are constantly moving around in gaseous or liquid form, moving randomly from one place or another. The greater the concentration of water molecules in a system or solution, the greater the total kinetic energy, and the higher its water potential. This means, that as the concentration of glucose increases in a solution, the concentration of water decreases, lessening the solution’s water potential, and lessening its ability to move between solutions by osmosis.
Relating this to the potato chips: basically, as the concentration of glucose in each solution increases, the water in that solution is less able to move to the potato as there is a higher concentration of water in the potato chip than in the highly concentrated sucrose solution, causing water from the potato to move to the solution, thereby achieving a percentage loss in mass. At concentrations such as 0.0molL-1 and 0.9molL-1, the concentration gradient is steeper; therefore the rate of diffusion is quicker. For the potato chips in the hypertonic 0.9 sucrose solution, the concentration of water molecules in the potato chip cells is greater than the water molecules in the 0.9 sucrose solution. This means that through the process of osmosis, water molecules will move from the potato cell through its semi permeable membrane and into the sucrose solution, therefore resulting in a percentage loss in mass of the potato chips as depicted by my results (a loss of XXX%), thereby justifying why the potato chips in the 0.9 sucrose solution being plasmolyzed.
In comparison, in the hypotonic tap water solution, the tap water with no sucrose solution (0.0) will have greater water concentration compared to the potato chip, forming a steeper concentration gradient. This means that through the process of osmosis, water molecules will move from the tap water solution through the potato chip cell’s semi permeable membrane and into the sucrose solution resulting in the rate of water movement from the tap water solution to the cells in the potato chips to be quicker, resulting in a net percentage gain of mass as shown by my results (a gain of XXX%), therefore justifying why the potato chips in the tap water solution became turgid. As the potato chips are placed into sucrose solutions which concentrations of sucrose are closer to the approximate isotonic range (0.1-0.2), the concentration gradient between the semi permeable membrane of the potato chip cells and sucrose solutions decreases, thereby resulting in the potato chips in the 0.1 solution having only a slight percentage mass increase while the potato chips in the 0.3 sucrose solution having a lower percentage mass loss compared to the potato chips in the 0.9 sucrose solution over the approximate 24-hour period.
In the living cell, both the cell wall and plasma membrane determine the permeability of the cell, but the latter of the two is the least permeable of the two. The ability of a substance to pass through these barriers is known as the permeation of the substance. Since not all substances may pass into or out of the cell, the cell surface is known as selectively permeable or as a semi permeable membrane. The semi permeability varies from cell to cell and under certain conditions. A solution in which the concentration of sucrose is greater than that inside the cell is called a Hypertonic solution and will cause a cell to become plasmolyzed.
An example of this in my results is the test at 1 molar. In other words, it becomes dehydrated and loses water through plasmolysis. If the concentration of the sucrose solution outside the cell is less than that inside the cell, this means that the solution is Hypotonic to the cells of the potato chip. The water will diffuse into the cells, making it turgid. This would explain why potato chips put into a solution of 0 molar seemed very firm compared to the potato chip used for 1 molar, this was because the cells of the potato had lost their turgor, and had become flaccid.
To conclude this, I can say that the movement of water through a selectively permeable membrane is affected by concentration of glucose solution, or by any other solution. The higher the concentration of glucose solution, the potato chip will have a net percentage loss in mass.