Osmosis in potatoes

Investigating how various solution concentrations affect the number of potato cores obtained through osmosis [Aim: To determine the concentration of the potato cytoplasm]

1. 6 beakers (60ml)
2. Sucrose Solution of different concentrations
   • 0M
   • 0.2M
   • 0.4M
   • 0.6M
   • 0.8M
   • 1M
3. 1 Potato Corner
4. 2 Large Potatoes
5. 1 30cm Ruler
6. 1 Digital Mass Scale
7. 1 Scalpel
8. 1 Forceps

1. Setting up the sucrose solutions
   • Prepare 6 beakers and label each of them chronologically with a concentration of sucrose solution. (See Figure 1.1)
   • Pour 40ml of the sucrose solution into the beaker with their respective concentrations, and set aside.
2. Preparing the potato cores
   • Using a potato corer, core 6 potatoes from the center of the potato. With a scalpel, ensure to cut off any excess potato skin on the sides.
   • Using a ruler, measure the potato cores to 3cm, and with the scalpel cut off any excess lengths.
3. Measuring initial mass
   • Using the digital mass scale, measure the mass of each potato core and note down their mass on a table with the associated concentrated solution they will be submerged into. This is the initial mass.
   • Reset the scale to 0 when switching between potato cores.
4. Placing the potato cores into the sucrose solutions
   • Place each potato core gently into its associated sucrose solutions.
   • Using a stopwatch, leave them in the beakers for 24 hours.
5. Measuring final mass
   • After 24 hours, remove the potato core from the solution using forceps.
   • Place the potato core onto the scale, and record their final mass on the table, alongside their associated concentrations.
   • Before measuring the next potato cores, wipe any water off the balance scale and reset the scale to 0.
6. Repeat
   • Repeat stages 1-5 two more times for the reliability of the experiment, and ensure to record initial mass and final mass onto the same table. (Figure 1.2 for reference)
   • An average for each concentration can then be calculated.

The results from Castle are presented in the table below, demonstrating how varying sucrose concentrations (M) affect the bulk of the potato cores (g) after 24 hours.

The table below arranges the mass of the potato cores side by side for simpler comparison as we investigate how sugar concentration influences it. A graph of the results is also made using the table.

y = -24.2x +19.6
*y is the average percent change in mass (%), and x is the sucrose concentration (M)

Solving for 0% Change in mass:

y = -24.2x + 19.6
*Substitute 0 into the y variable and rearrange
0.8099173554 = x

∴ = 0.81 M

It is significant to note that Castle determined that a mass change of 0% on average was caused by a sucrose solution concentration of 0.823M using the equation: y = -23.586x + 19.41.

There must’ve been a calculation error somewhere (mine or hers) that concluded in different trendline equations. We may still evaluate the data and draw conclusions from the graph and tables that were previously provided because I used her results.

Looking at graph 1.1, there is a negative connection showing that as the concentration of the sucrose solution increases, the average percentage change in mass drops. This demonstrates that when the independent variable [concentration] increases, the dependent variable [change in mass] decreases, indicating that the change in mass is inversely related to the concentration of sucrose.

There is a 21.3% change in mass for a sucrose solution of 0M, as shown in Table 2.2. The mass change caused by this concentration number is the largest overall, and it only gets smaller as concentrations get higher.

The experiment was successful in determining the cytoplasmic concentration of the potato. At that time, the average mass change was 0%. As there was no change in mass, showing that the solution was isotonic and that the solution and the cytoplasm had the same concentration (0.81M), we can be certain that this is referring to the cytoplasm of the potato. As a result of their same osmolarity, there is no net water flow.

The average change in mass for a concentration of 0M was a 21.3% change in mass, meaning that the potato gained weight. This proves that the solution was hypotonic since there was a net water flow into the potato. Osmosis, which is the transport of water molecules over a semipermeable membrane from a region of low solute concentration to an area of high solute concentration, is what causes this to happen. In this case, the migration of water into the potato was caused by the concentration of the potato being substantially higher than the solution.

The average change in mass for the concentration of 1M was -4.3%, which is also evident there. This demonstrates that the potato became lighter, showing a net movement of water out of the potato, proving the solution was hypertonic.

To assess accuracy, we can contrast Castle's findings with those of other lab studies. Of course, hero, I discovered one that stated that their potato's cytoplasm concentration was 0.225M. Comparing this to Castles is a huge departure. The cytoplasm of the potato used in BioLab's experiment had a salt concentration of roughly 1.2g/100 mL, however, it is difficult to compare their results to Castle's because they measured their concentrations differently. I also came across one by Alveena Majeed, who stated that the cytoplasm of their potato was 0.197M. Instead of sucrose, they utilized a solution of glucose. Castle's results appear to be considerably different from those of other studies, however, this may be because the potato used and the concentration measurements used were different. This isn't the most effective approach to judge the accuracy, but we can infer that Castle's method isn't the most accurate for calculating a potato's cytoplasm content.

We won't be calculating experimental error because there isn't a concentration generally acknowledged to represent a potato's osmolarity. The evaluation will go into more detail about other errors.