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Transport in Plants

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Introduction

AN INVESTIGATION ON THE PROCESS OF OSMOSIS BETWEEN POTATO CELLS AND DIFFERENT CONCENTRATIONS OF SUGAR SOLUTIONS AIM: To investigate the effect of varying concentration of a certain sugar solution on the amount of osmosis between the solution and potato strips by calculating the difference in the mass of the potato strips before and after a day, in order to find the isotonic point. HYPOTHESIS: I think that the mass of those potato strips which would be kept in low concentrations of sugar solution will increase because the concentration of water molecules will be higher in the solution than inside the potato cells itself (We know that osmosis occurs down the concentration gradient). Likewise, the mass of the potato strips will decrease when kept in highly concentrated sugar solution because the concentration of water molecules will then be lower in the solution than in the potato cells. THE VARIABLES: * Independent: The concentration of the sugar solutions * Dependent: Change in mass of the potato strips * Control: o Volume of the solution (30 cm3; I ensured that the potato strips were submerged completely inside the solution) o Shape of the potato strips (cuboid); As the shape varies, so does the surface area in contact with the solution o Same type/quality of potato o Temperature of the solution (more osmotic activity would happen if the temperature is higher) ...read more.

Middle

intersects the x-axis. OBSERVATION: RAW DATA TABLES CONCENTRATION OF THE SUGAR SOLUTION (M) MASS OF THE POTATO (g) UNCERTAINTY � 0.01 g UNCERTAINTY � 0.01 g UNCERTAINTY � 0.01 g 0.0 2.18 1.92 2.07 0.1 2.96 1.46 2.09 0.2 1.94 1.13 2.05 0.3 1.08 1.08 1.13 0.4 2.01 1.18 1.43 0.5 1.21 1.26 1.42 CONCENTRATION OF THE SUGAR SOLUTION (M) MASS OF THE POTATO (g) UNCERTAINTY � 0.01 g UNCERTAINTY � 0.01 g UNCERTAINTY � 0.01 g 0.0 2.81 2.68 2.75 0.1 3.40 1.85 2.41 0.2 2.11 1.21 2.25 0.3 1.10 1.02 1.23 0.4 1.64 0.86 1.09 0.5 0.79 0.81 1.01 PROCESSED DATA TABLES: CONCENTRATION OF SUGAR SOLUTION (M) 0.0 0.63 0.76 0.68 0.69 0.1 0.44 0.39 0.32 0.38 0.2 0.17 0.08 0.20 0.15 0.3 0.02 -0.06 0.10 0.02 0.4 -0.37 -0.32 -0.34 -0.34 0.5 -0.42 -0.45 -0.41 -0.43 * To find the change in mass, I subtracted the mass of the potato strip before from the mass of the potato strip after. This is expressed as: CHANGE IN MASS = MASS AFTER - MASS BEFORE * To find the average, I added the mass difference calculated for each of the three strips (before and after), and divided this sum by 3. ...read more.

Conclusion

As the water potential of the solutions was higher, water was transported into the potato cells, causing the potato strips to bloat and the cells to become turgid. In biological terms, this process is more specifically known as endosmosis, and occurs in hypotonic solutions. A hypotonic solution is one where the concentration of water molecules is less in the solute than in the solvent. My hypothesis is proven correct. EVALUATION: Factors that could have caused inaccuracy: * While labeling the potato strips, I used a gel pen once for the third strip in the 0.3 M sugar solution. A small amount of ink might have diffused from the potato strip into the solution, which was why I obtained an anomaly in that case. * All the potato strips were handled with bare hands, which implies that impurities from the hands mixed with these strips. This must have affected the osmotic activity between the potato and the solution. * The beakers were left uncovered, meaning that: i. Any impurity from the surroundings could have mixed with the solution- again affecting the osmotic activity between the potato cells and the sugar solution. ii. A small portion of the solution might have evaporated, leaving the upper surface of the potato strips unexposed to the solution ?? ?? ?? ?? FINDING THE ISOTONIC POINT OF POTATO CELLS 1 ...read more.

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