The movement of water molecules across a semi-permeable membrane is the process of osmosis. If there is a solute and a solvent, each containing different concentration levels, then the water would move along its concentration gradient until each side of the membrane are equal. The water moves because the membrane is impermeable to the solute and the solute concentrations may differ on either side of the membrane. Water molecules may move in and out of the cell, but there is no net diffusion of water. Water will move in one direction or the other, and this is determined by the solute or solvents concentration levels. If the two solutions are of equal concentrations, they will be isotonic. If the concentrations are unequal, the solution with the higher concentration is hypertonic, and the solution with the lower concentration is hypotonic. What is the solute concentration of potatoes? We can determine this by conducting an experiment in which involves the process of osmosis. Potatoes are full of sucrose used for energy storage in plants. Sucrose is a carbohydrate found in food. It is a disaccharide, with a combination of fructose and glucose. Consumers break sucrose down into two monosaccharides so they can be absorbed more easily into the blood. Sucrose is too large of a molecule to diffuse through a semi-permeable membrane, and therefore needing to be broken down so they can move in and out of cells effectively. If potatoes are placed in a solute containing sucrose, then a concentration gradient would be present and the process of osmosis would naturally occur by moving water through the semi-permeable membranes. If the concentration of sucrose in the solution is less than the concentration of sucrose found in the potato, then the potato would decrease in mass. The opposite would occur as well, if the concentration of sucrose in the solution is more than that of the potato, then the potato would expand and gain in mass. In conducting this as an experiment, we can determine what the solute concentration of potatoes is.
The materials used to conduct this experiment are as follows: * Test Tubes
* Test-tube Rack
* One 100mL Beaker
* One 50mL Beaker
* Distilled Water
* Paper Towels
* Marker for Test Tubes
* 1 mol/L Sucrose Solution
* 2 Pipettes
* 10 mL Graduated Cylinder
* Electronic Balance
* Razor Blade/Scalpel
Figure 1.0: Cutting of potatoes, weighing of potatoes, and potatoes placed in sucrose solution. In figure 1.0, we can see that the potatoes were cut with a scalpel into thin slices so they could fit the test tubes appropriately. Then their mass was recorded using the electronic scale. They were placed into the test tubes containing sucrose and were to be left on the test tube rack over a 24 hour radius. The next day, the potato slices were to be taken out and measured again.
It is important for one to be careful using sharp instruments. It is also recommended for one to wear safety glasses and an apron to prevent mess or solution to come into contact with eyes.
Using the marker, we labeled the test tubes 1-6. Using a pipette, we added the correct amount of water to each test tube, as well as with the sucrose solution. For that, we used the following table: Test Tube Number| 1| 2| 3| 4| 5| 6|
Volume of Water (mL)| 10| 8| 6| 4| 2| 0|
Volume of Sucrose (mL)| 0| 2| 4| 6| 8| 10|
Solute Concentration (mol.L-1)| 0| 0.2| 0.4| 0.6| 0.8| 1.0| Figure 1.1: Solute Concentration
After filling the test tubes, we had cut for us 6 equal sized potato sections. We rinsed the sections with distilled water and blotted them dry with paper towel. We weighted them using an electric balance and recorded it into the table. After 24 hours, we removed each potato section and gently blotted it dry. We recorded the final measurements using the following calculations: 1....