Diffusion is the net movement of particles from an area of higher concentration to an area of a lower concentration, and osmosis is the net movement of water across a selective permeable membrane (Biology Department, 2008). The molecules can enter and leave the cell through a selective permeable membrane which allows molecules to enter the cells cytoplasm depending on their size, hydrophobicity and charge. There three types of water movement in osmosis. First is the isotonic solution which has no net water movement which means the concentrations inside and outside the cell is equal and the cell reached equilibrium. Hypertonic solution is when the water moves outside the ...view middle of the document...
The concentrations varied from 0 to 0.6 M. From a potato, 4 pieces were cut into small cubes with a size of 1cm x 1cm x 1cm. The potato pieces were always placed on a wax paper or a plastic wrap and not on a paper towel because it will draw water from the tissues. For each potato piece, it was weighed individually with a Denver Instrument MXX-212 balance. The weight of each piece was recorded in a table and each piece was placed in a different test tube. 10ml of each solution of different concentrations was poured in each test tube with the same concentration labeled on the tube. The potato pieces were left for incubation for an hour at room temperature. After the incubation, each potato piece was weighed again using the same balance mentioned earlier. The new measurements were recorded in the table and the percentage of weight change was calculated and recorded in the same table. The formula to calculate the percentage of weight change is:
[ (weight after-weight before) / weight before ] x 100 = % weight change.
The second part of the experiment was to see how the surface area and volume effects the diffusion of water in and out of the cells. Two pieces of potato were cut with a size 1cm x 1cm x 1cm and 2cm x 2cm x 2cm. The two pieces were weighed using a Denver Instrument MXX-212 balance. The weight of each piece is recorded in a new table. Both of the potato pieces were placed in a beaker and covered with distilled water and were left for an hour for incubation at room temperature. After the incubation period was over, each potato piece was weighed again using the mentioned balance and the values were recorded in the table. The percentage of weight change was calculated as well as the surface area, volume, and the ratio of surface area to volume. The surface area of a cube is six multiplied by the square of the length of the side (6a2). The volume of the cube is the length of the side to the power of three (a3).
The final part of the experiment is to examine the effects of osmosis in plant cells, specifically, red onion cells (Allium haematochiton). A very thin red leaf epidermal peel was obtained from a red onion and was placed on a microscope slide and submerged in two drops of isotonic saline (0.9% w/v NaCl). Two other red onion peels were prepared and submerged in mystery solution A and B, both solutions on each peel. After the onion peels were left for five minutes to equilibrate in the solutions, coverslips were placed on the slides and were examined under the microscope (Leica DME) using a 10x objective. A labeled drawing was prepared for each onion peel.
Table 1. Weight of potato sections before and after incubation in different concentrations of sucrose.
Sucrose Concentration (M) Weight before (g) Weight after (g) Percent weight change
0 1.55 1.70 9.68%
0.2 1.62 1.72 6.17%
0.4 1.66 1.62 - 2.44%
0.6 1.56 1.45 - 7.05%
According to Table 1, the potato pieces of the first part of the experiment had different...