Determining the Isotonic Point of Potatoes in Sucrose Solution

Determining the Isotonic Point of Potatoes in Sucrose Solution

Done by: Shaunik Sharma, Shehzer Numani, Kristine Palaca, Hannah.

Submitted to: Ms. De Souza

Date: October 17, 2016

Introduction:

No living organisms were harmed during this experiment. The goal of this lab was to find the isotonic point of a Solanum tuberosum, to determine the amount of sucrose solution in it. In order to find the isotonic point, you first need some background information on osmosis. As such, osmosis is the transport of water molecules in and out of the cell from low solute concentration to high solute concentration. During osmosis, different amounts of solutes affect the structure of the cell in different ways. When the solution is hypertonic, there are more solutes outside than inside of the cell which, causes the cell to plasmolyze due to water loss. However, when the solution is hypotonic, there is more water than the cell's contents, making the cell turgid and expanded. Isotonic, is when there are equal concentrations of water and solute inside the cell as outside, and diffusion continues at an equilibrium. Each type of cell is unique in reaching this equilibrium, and this is known as their isotonic point. We were taught osmosis in our class and were introduced into the process of it. We were keen on learning how it happened and learning to see the in real life apparatus of it being used. Being taught a concept such as osmosis is one thing however, being able to hands on "prove" that the concept is actually true; makes the learning experience that much more enjoyable and significant.  As, seeing the osmosis take place in real life helped us to understand and appreciate this concept.

Research Question:

What is the isotonic point of the white potato, Solanum tuberosum?

Hypothesis:

If a potato sample is put in a sucrose solution with a concentration 0.333 mol/L, then there will be no net change in mass, because the potato has reached its isotonic point.

Variables:

Materials:

One white potato (solanum tuberosum).

100 mL of sucrose solution with a concentration of 1mol/L.

100 mL of distilled water (H2O).

Apparatus:

1 test tube rack (capable of holding 12 test tubes).

10 rubber stoppers.

Graduated cylinder of 100mL.

Beaker of 150mL.

Beaker of 300mL.

2 scalpels (21 blade).

Plastic ruler (15cm)

Electronic balance (±0.01g)

Cork boar

Procedure:

1. One white potato were obtained, Solanum tuberosum.
2. Use a boring tool to obtain 10 potato samples.
3. Cut each of the 10 potato samples, using a scalpel and a plastic rules, into a length of 4.5 centimeters.
4. The mass of each of the potato samples were measure on electronic balance and recorded.
5. Poured 20ml of water into two test tubes to create two samples of 0 mol/L solution.
6. Poured 20 ml of sucrose solution into two test tubes to create two samples of 1 mol/L solution.
7. Poured 10 ml of 1 mol/L sucrose solution and 10 ml of distilled water into two test tubes to create two samples of 0.5 mol/L sucrose solutions.
8. Poured 15 ml of distilled water and 5 ml of 1 mol/L sucrose solutions into two test tubes to create two samples of 0.25 mol/L sucrose solutions.
9. Poured 15 ml of 1mol/L of sucrose solution and 5 ml of distilled water into two test tubes to create two samples of 0.75 mol/L sucrose solutions.
10. Placed one sample of potato into each of the 10 test tubes.
11. Placed rubber stoppers into the test tubes to create an airtight environment.
12. Kept the test tubes in a test tube rack for 24 hours.
13. After 24 hours, the test tubes were emptied, the potatoes were taken out using a scoopula and the mass of each of the potato samples was measure using the same electronic balance and recorded.
14. The percent net change in mass and the percent uncertainty for each of the five different concentrations of sucrose solution were calculated and recorded.
15. The mean percent change in mass and the mean percent uncertainty was calculated and recorded.

Observations:

Figure 1: Illustrates the raw date from the experiment.