Glucose Concentrations On Osmosis Essay, Research Paper

Studying the Effect of Various Glucose Concentrations on Osmosis in a Potato

Osmosis is the process in which water particles move from an area of high water concentration to an area of low water concentration through a semi-permeable membrane until the concentrations are equal.

Osmosis has the same basic theory as diffusion. Particles are moving from an area where they are in great concentration to an area where they are in low concentration until the concentrations are the same. Osmosis is this movement of water particles and the particles must move through a semi or partially permeable membrane (a membrane that lets some things through but not others). An example of this type of membrane is a cell wall, like in a potato. Osmosis occurs when two things occur. One is if the cell has no water in it or has less water then the solution it is placed in. If this is the case then water will go from the solution, for it is the area of high water concentration, into the cell, for this is the area of low water concentration. If the cell has no water within it the cell is flaccid. As the water passes through the cell membrane, the cell fills with water and becomes turgid. Once the cell becomes turgid, no more water can enter the cell and osmosis stops.

The other incident that can happen for osmosis to occur, is when the concentration of sugars or other minerals in the cell is different then that of the solution it is placed in. This is because the amount of sugar in the water either in the cell or in the solution is going to change the water concentrations as well. Whichever solution, either in the cell or not, contains a higher sugar concentration will have a lower water concentration. If the solution in the cell contains more sugar, salt or other minerals then the solution it is placed in, then it will have a lower water concentration. This will cause water from the external solution to pass through the cell?s semi-permeable membrane into the cell to make the two concentrations equal. Osmosis would also occur if the external solution contained more sugar then the solution inside the cell. In this case, water from inside the cell would pass through the cell?s semi-permeable membrane into the external solution making the concentrations equal.

If we relate osmosis to the weight of our potato, we can see that if the potato cells lose water the weight of our potato decreases and if the potato cells gain water then the weight of our potato increases. We can determine the concentration of our potato by knowing this. If the potato increases in weight, then the solution outside the cell has a greater water concentration then that which is inside the cell. We know this because water must have entered the cell through its membrane because the water was moving from an area of high water concentration (the external solution) to an area of low water concentration (inside the cell) until the concentrations were equal. If the potato decreases in weight, then the solution inside the cell has a greater water concentration then that which is outside the cell. We know this because the water must have left the cell through its membrane because the water was moving from an area of high water concentration (the inside of the cell) to an area of low water concentration (the external solution) until the concentrations were equal.

Diagram of Apparatus

Apparatus

Potato

Glucose Solution

Boiling Tubes and Rack

Scale

Method

1. Set up apparatus as shown in diagram.

2. Cut potato squares into equal lengths and widths. My potatoes were 3cm long and 1cm wide.

3. Number or mark each potato so that they can be identified 1 through 16.

4. Dry and weigh each potato piece and record your findings.

5. Put 4 of your potatoes in a solution of 1 molar glucose, 4 in a solution of .6 molars of glucose, 4 in a solution of .4 molars of glucose, and 4 in 0 molars of glucose or water. They are all placed in boiling tubes. Use 10 cm of solution.

6. Leave them to sit for 20 minutes.

7. Dry and reweigh each potato.

8. Record their new weight and make graphs.

9. Repeat three times for averages.

Note: Due to the short time we had to work on this experiment, we were unable to repeat the experiment three times. Therefore we only have one set of results.

Fair Test

To make this experiment a fair one, there were many things we had to ensure happened.

 Repeat the experiment three times and take averages.

 Use the same volume of glucose solution even though it is not in the same concentration. I used 10 cm of glucose solution.

 Use the same size pieces of potatoes. Mine were 3 cm by 1cm.

 Let them sit for the same amount of time before taking them out to be weighed. I left them for 20 minutes.

 Dry the potatoes before you weigh them. This will remove the excess water from the surface of the potato hence giving you a more accurate result.