Osmosis Lab Report

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Osmosis is the net movement of water from an area of high concentration to an area of low concentration. The process was first studied in 1877 by a German physiologist, Wilhelm Pfeffer. The general term osmose, now osmosis, was introduced in 1854 by a British chemist, Thomas Graham. (Britannica, n.d). This lab shows the rate of osmosis between three different concentrated cells and their outer environment. The dialysis tube mimicked the purpose of a cell membrane and the water in the beaker acted as the exterior environment. It was hypothesized that as the concentration gradient increases, so does the rate of osmosis; the greater the concentration difference, the faster the rate of osmosis. This was what was shown throughout this lab the dialysis…show more content…
The qualitative data shows that near the end of the lab the starch solution inside the dialysis tube was blue this was because the iodine solution diffused through the tube and caused the starch to change colour, as shown in Table 2.0. At 0 minutes, the mass of the starch solution inside the dialysis tube was 10.00 g. After 30 minutes of conducting the lab the mass of the starch was 11.02 g, which proves that the mass increased because iodine diffused inside the dialysis tube. Pfeffer’s work on cell metabolism led to his work in 1877 in devising a semi-permeable membrane that he used to study osmosis. He developed a method for measuring osmotic pressure and showed that pressure depended on the size of the molecules too large to pass through the membrane (Britannica, n.d). The rate of osmosis for the experiment was 0.034, representing a hypotonic solution. Starch is a polysaccharide made of glucose monomers joined in α 1,4 linkages. The simplest form of starch is the linear polymer amylose and amylopectin is the branched form. Since it is a polysaccharide the molecules of the glucose and water mixed together do not diffuse through the dialysis tubes easily because of the cell structure of starch. Thus proving the hypothesis of the experiment since the particle size of iodine was smaller compared to starch, iodine diffused across the membrane faster.…show more content…
These tubes have minimal polarity which indicates that these tubes operate by only particle size, not the molecule nature. However, in real life, the cell membrane does not only operate based on the size of the molecules diffusing in or out but, rather the nature of the molecule as well. The cell membrane contains a phospholipid bilayer, cholesterol, carbohydrates, and membrane proteins such as integral and peripheral proteins. The proteins contain sugar chains which are known as glycocalyx. These sugar chains assist in cell to cell recognition and cell communication. However, the dialysis tube does not contain these proteins, and the glycocalyx, which prevents it from accepting other molecules that simply cannot diffuse through its pores. These proteins help large, polar, or charged molecules to travel through the cell membrane because they do not simply diffuse through the cell membrane. This is due to the structure of the phospholipid bilayer. It has phosphate heads that are polar (hydrophilic) and it has fatty acid tails that are non-polar (hydrophobic). It does not allow polar molecules to pass through because majority of the bilayer consists of non-polar molecules. In addition, the cholesterol maintains

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