Diffusion and Osmosis Essay

Diffusion and osmosis are very important in biological process. Diffusion is the movement of molecules or ions from a region of their high concentration to a region of their low concentration. Osmosis is the diffusion of water molecules across a semipermeable membrane. To gain a better understanding of diffusion and osmosis, we examine multiple experiments to show diffusion and osmosis in animal cell, plant cell and synthetic cell. In our first experiment, we weight a decalcified chicken egg and place 10% NaCl concentration.

At every fifteen minutes intervals, we weight the egg and record that the weight decreases. In our second experiment, we use three slices of aquatic plant Elodea and add pond water one leaf, distilled water for the second and 20% NaCl for the third, then observe the cells of each leaf with a compound microscope.

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Under microscope, chloroplasts (green organelles) in Elodea tend to bound to the cell wall in pond water, spread all over the cell in distilled water, pull away from cell wall in 20% NaCl.

In our last experiment, we use a dialysis bag that contains 30% glucose and starch solution then place into a beaker of water and iodine solution. We then remove the bag out of the beaker, and use two test tube which label BAG, BEAKER to perform a Benedict’s test. We place solution in the bag in the BAG tube, and solution in the beaker in the BEAKER tube and add a drop of Benedict’s reagent to each tube, then heat each test tube and observe a color change in each tube. These experiments show that movement of water of chicken egg cell and Elodea cell is “osmosis” and movement of molecules in dialysis bag and beaker is “diffusion”.


Diffusion is involved in many biological processes occurring in single-celled to complex organism (cite this). It is a part in life that we need to know and understand how it works. Diffusion is the process by which molecules move from an area of high concentration to an area of low concentration (cite this). A branch of diffusion process is osmosis, which is the movement of water across a membrane which is selectively permeable (cite this). We are going to learn and get more information about diffusion osmosis by perform three experiments. We place a shell-less chicken egg in salt solution. We predict that water in the egg will move out the cell because this is a hypertonic solution, a greater concentration of osmotically active substance than the solution on the other side of membrane.

Next, we are going have three slices of Elodea in each different solution: hypotonic, isotonic, hypertonic then we observe these reactions in the microscope. We predict that one will have chloroplasts (green organelles) bound to cell wall in hypotonic, one will have chloroplasts move in the cytoplasm, one will have cell wall remain intact and chloroplasts move away from cell wall. Third, we’re going to use a dialysis bag contains starch and glucose and place in water and iodine solution. After a Benedict test, we predict that there will be color change in these solutions. These experiments are easy to perform and they also give people enough information to gain better concepts of how diffusion works in animal cell, plant cell, and synthetic cell.


First, we performed an experiment to show osmosis in animal cell. Our materials in this experiment were a decalcified egg, a 350mL beaker, 10% of NaCl solution, a triple beam balance, and a timer. We used the triple beam balance to weigh the egg. The weight of the egg was 77.3g at this time. Next, we placed the egg in the beaker that was filled with 250mL of 10% NaCl. We waited about fifteen minutes and then remove the egg out of the beaker. We dried off the water from the egg and placed the egg on the triple beam balance. The weight of the egg after fifteen minutes was 76.6g. We then placed the egg back in the beaker and repeated these steps every fifteen minutes intervals. At thirty minutes, the egg’s weight was 76.3g. At forty-five minutes, the weight was 76.2g. At sixty minutes, the weight was 76.1g. We recorded the data and calculated the percent change in egg weight by using the weight at the present time minus the previous weight all over the previous time and all multiply to one hundred. We then graphed our data to show percent changes in weight of the egg.

Next, we performed another experiment to show osmosis in a plant cell. We used leaf of the aquatic plant Elodea, pond water, distilled water, 20% NaCl solution, a compound microscope, a pair of forceps. First, we cut three small pieces from Elodea plant with forceps. We then carefully placed each piece onto the microscope slide glass. We added a small drop of pond water to one piece and labeled it “pond water”. We added a small drop of distilled water to another piece and labeled it “distilled water”. Last we added 20% NaCl to the last piece and labeled it “20% NaCl”. We waited for ten minutes and then we observed the cells of each piece of leaf under the microscope. We then sketched the cells of each piece as seen in the microscope. In our last experiment of diffusion of synthetic cell, we used a 30-cm strip of moist dialysis tubing, a string, 30 % glucose solution, starch solution, iodine solution, Benedict’s reagent, hot plate, 500-mL beaker one-third filled with water, handled test tube holder, 3 standard test tubes, disposable transfer pipettes, two of 400-mL beakers to hold dialysis bag.

First, we soaked the dialysis tubing in water and closed one end with a string, and let the other end open. Then we added four pipettesful of 30% glucose into the bag and four pipettesful of starch solution to the glucose in the bag. We gently mixed the contents and observed the color in the bag. Next, we add 300mL of water to 500mL beaker. We put some drops of iodine solution in the water and it turned into a brown color. After that, we placed the dialysis bag into the beaker and waited for thirty minutes. After thirty minutes, we moved the bag and let it stand in a dry beaker. We then recorded the data. Next, we used two test tube which labeled “BEAKER” and “BAG” for the Benedict’s test. We put two pipettesful of the bag solution in the BAG tube and two pipettesful of the beaker solution in the BEAKER tube. We added a drop of benedict’s reagent to each tube and heat them up in hot water for three minutes. After three minutes, we observed the color change and recorded our data.


In our first experiment with decalcified egg in 10% NaCl, we find that the weight of the shell-less egg decreases after every fifteen minutes time interval. At time zero, the egg has 77.3g but after fifteen minutes, the egg has 76.6, a -0.9% change in weight. At thirty minutes, the egg has 76.3g, a -0.4% change in weight. At forty-five minutes, the egg has 76.2g, a -0.1% change in weight. At sixty minutes, the egg has 76.1g, a -0.1% change in weight.

In our second experiment with Elodea plant, we find that chloroplasts(green organelles) of Elodea cell in pond water moves close to cell wall. In distilled water, we find that chloroplasts (green organelles) of Elodea cell move freely through out in the cytoplasm but block by cell wall. We also find that chloroplasts (green organelles) of Elodea cell of in 20% NaCl moving away from the cell wall and form tightly in the central of cytoplasm. In our last experiment with dialysis tubing, we observe some color change. The bag solution, which contains glucose and starch, has a transparent original color, turns to transparent with some black dots as final color. After using the Benedict’s reagent, the tube which contains the bag solution turns into an orange color.

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