Diffusion Across Biological Membranes Essay Example for Free

Diffusion Across Biological Membranes Essay From the cell simulation modal made, it has explained about the aspects of diffusion and indicator solution (chemical testing) to test for particular substances. From the observation made, iodine and glucose have greater concentration due to small molecular size and also they are monomers. It means their molecules are smaller. Thus, it diffused out to create a state of equilibrium. On the other hand, starch molecules did not move by diffusion across a membrane into or out of the cell due to the large molecular side. This is because many repeated glucose subunits are found in starch structure. Starch is a polymer. This is the reason why the water in the beaker or 1 inch dialysis tube did not turn dark blue as no starch molecules diffuse out. However, the liquid outside of cell was cloudy. When iodine indicator and Benedict’s test, tested for presence of iodine and glucose respectively, the colour change was not very distinctive. Hence, we came to a rationale that more time could have needed for glucose and iodine achieve diffusion as 1 hour was not enough to complete as perhaps molecules on one side of a membrane become trapped by binding to macromolecule. On the other hand, perhaps water in the beaker could have been too diluted so could not detect the presence of glucose and iodine using indicators. This process is termed as osmosis. In osmosis, molecules also travel from higher concentration to lower concentration. However, osmosis only occurs in water. Water molecules are polar and small enough to pass through the membrane. Therefore, from this experiment, we can understand that water is essential for cells survival. However, too much of water will result in hypotonic. ells is placed with a lower concentration, then osmotic pressure of the extracellular fluid is less than intracellular fluid. As a result, water flow into the cell causing it to swell and undergo lysis (burst). Likewise, if a cell is placed into a solution with higher osmotic concentration than the intracellular fluid such as salt solution. The osmotic pressure of the extracellular fluid will exceed that of the intracellular fluid casing the cell to shrink and crenate. Hence, it’s hypertonic. This explains why when a small dose of fertilizer can enhance plant growth but over fertilization can kill the plant. Fertilization has salt and salt dehydrates the cytoplasm in the cell and would dry up making the cells shrivel up and die. Iodine indicators and Benedict’s solution proved that when a substance reacts with its indicator solution, a reaction will occur and cause a colour change. In this case, iodine test used to test for the presence of iodine in the solution and Benedict’s solution is use to detect glucose. It is important for Benedict’s solution to be heated as it’s a way to prove that it is the mixing of the two that creates the bright orange colour. If the benedict’s solutions were to be heated separately or the solution to be heated there will not be any results produced to test the presence of glucose. The indicator solution will react only if the substance is meant for is present, then it will react. Else there would not be any changes to observe. Indicators come in handy when dealing with unknown samples of ingredients to prove what a substance is. A negative control is used yield a negative result. This is to ensure that all the reagents are pure and there is no contamination that will give a false result. Conclusion In conclusion, we can conclude that diffusion occur spontaneously and molecular size and charges matters when molecule pass thought cell membrane unless its molecular size is small and it’s a monomer diffusion will occur spontaneously. However, if the molecular size is big and it might also hinders the passage way for smaller molecules to diffuse to a higher concentration to lower concentration to bring it to an equilibrium state. We also concluded that cell should maintain a isotonic environment to conduct its activity smoothly else in hypertonic or hypotonic, it will burst or shrivel and eventually kills the cell. Therefore, diffusion and osmosis are types of passive transport and happens spontaneously.