Osmosis Lab Report Essay, Research Paper

Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Diffusion results because of the random movement of particles. The diffusion of water into and out of a selectively permeable membrane is called osmosis. Because of the selectively permeable membrane, nothing but water and other very small particles can be diffused through osmosis. The cell membrane is similar to the membrane mentioned above, so the cell would lose water because of osmosis if it were placed in an environment in which water concentration is greater than that of the cell.

A solution is isotonic if the concentration of dissolved substances is the same as the concentration inside the cell. Osmosis does not occur in an isotonic solution. A hypotonic solution is a solution in which the concentration of dissolved substances is lower than the concentration inside the cell. If a cell were put in a hypotonic solution, osmosis will cause water to move through the cell membrane into the cell. A solution is hypertonic if its concentration of dissolved substances is greater than the concentration inside the cell. If a cell were placed in a hypertonic solution, it would lose water. All particles that pass through the plasma membrane by the process of diffusion do not require energy, so their movement is called passive transport. The transport of materials against a concentration gradient requires energy, so it is called active transport.

The purpose of this experiment was to make observations and conclusions about the ability of cells to adjust to varying chemical concentrations in the environment and to observe the effect of isotonic, hypotonic and hypertonic solutions on cells. I hypothesize that when the sucrose concentration will change, the mass will also change.

For the experiment, the following materials were used: potatoes, petri dishes, a balance, a graduated cylinder, distilled water, sucrose solution and five beakers. Each of the beakers were labeled with a different sucrose concentration (0.0; 0.2; 0.4; 0.6; 0.8). Three potato cores equal in length and width were cut for each beaker, the cores are weighted and placed in the beakers. After that, the solutions are placed in the beaker according to their labels. The solutions will be in the beaker for twenty-four hours. After twenty0four hours, the cores are taken out of the solutions and blotted dry. Their mass is recorded in the Final Mass column of the data table. The percent change in mass is calculated and recorded for each sample.

The results supported my hypothesis because for the 0.0 sucrose concentration the percent change in mass was 15% for the 0.2 concentration, it was 0%, for 0.4 it was 2%, for the 0.6 concentration it was 29%, and for the 0.8 sucrose concentration, the percent change in mass was 38%.

The reason for the change in mass is the process of osmosis. When the sucrose concentration was 0, the cores gained weight because the concentration in the potato cells was different from the concentration outside (hypertonic), allowing more water to come in so it will reach a dynamic equilibrium with the outside of the cell. When the sucrose concentration was 0.2, it was an isotonic solution, so no major exchange of particles occurred between the potato cells and the sucrose solution. When the concentrations of sucrose were higher (0,4, 0.6 and 0.8), the outside solution was hypotonic, because the cell lost water to reach an equilibrium with the outside of the cell, so the cell lost a significant amount of weight.

One way the experiment could have been improved was to measure the size of the potato cores with more precision, otherwise, in my opinion, the experiment was flawless, and I think no errors could have been made. For future studies, one could use some other kinds of cells (animal perhaps) and measure the percent change in mass, or have more levels of sucrose concentrations (1.0, 1.2)