A Study of The Use of Osmosis on Dialysis Tube in Fresh and Salt Water Environments

Cells have been loosely defined as the building blocks of all living things. All cells are contained by cellular membranes, which provide structure for the cell (Cooper. G, 2000). The cell membrane is a semi permeable membrane that surrounds the cytoplasm of a cell and is made up of a phosphor lipid bi-layer (Cell Membrane, 2014). Cell diffusion occurs through the cell membrane as a mean of transport for substances going in and out of the cell (Nave R, n.d). Cell diffusion according to the Biology Corner, diffusion is the process by which molecules spread from areas of high concentration, to areas of low concentration (2012).

There are three main types of cell diffusion, these are; simple, channel and facilitated. Simple diffusion is when a particle with a neutral charge and small enough size to fit through the layer of phospholipids passes through the membrane. The molecule also has to be hydrophobic, so the protein can move to the external side of the membrane without being ‘rejected’ as hydrophilic molecules are. Channel diffusion is passive transport processes in which molecules that do not fit the requirements for simple diffusion use protein channels to pass through the cellular membrane. The facilitated diffusion process requires carrier proteins to move the molecules from one side of the membrane to the other (Diffusion, n.d).

Osmosis is the diffusion of water through the cell membrane from areas of lower solute concentration to higher solute concentrated areas (Khan, 2010). “In terms of osmosis, solute refers to all the molecules or ions dissolved in the water (the solvent)” (American society for Microbiology, 2013). Osmoregulation is related to osmosis, as it keeps the body’s fluids from becoming too diluted or concentrated. When the osmotic pressure of a solution is high, the more the water present wants to go into that solution (Rybicki, 2009). A hypotonic solution is when the concentration of the solute is less than that of the external side of the cell membrane. This is the opposite for hypertonic (All Nurses, 2011).

Animals and plants are multi-cellular and are specialised in their functions and roles in the body or organism. Cells in animals can have roles such as carrying oxygen in the body, and in plants they absorb sunlight, water and materials to achieve such processes as photosynthesis (BBC, 2014). This is the same in humans, as the cells in body are specialised, each carrying out their own roles. As a fish contains bodily fluids, and is always surrounding by a fluid environment, it uses the process of osmoregulation to maintain a balance of salt and fresh water in the fish’s body. Osmoregulation is also relative to osmotic pressure, as this pressure prevents osmosis from occurring into a specific solution when it is separated from the solvent by a semi-permeable membrane (Duxbury, 2012).

Aim

The aim of this experiment is to demonstrate the effect changes in environment has on osmosis through a semi permeable membrane

Hypothesis:

It is hypothesized that the distilled water should deluge into the beakers and dialysis tubes that contain the saline solutions of salt to dilute the solute due to osmoregulation (Saladin, 2000). It is also predicted that when the solutions are isotonic, the weights should be recurring (Innovateus, 2006).

Materials

• 4 x 100ml beakers
• 4 x dialysis tubing
• 4 x rubber bands
• Marking pen
• Distilled water
• Salt

Method

500 ml of distilled water was put in a beaker, and 17.5 grams of salt was measured on electronic scales and added. It was stirred until the salt dissolved to create a saline solution to act as the salt water for the experiment. Another 500 ml of distilled water was placed in a separate beaker to act as the fresh water for the experiment. 4 clear dialysis tubes were tied off in a knot at one end. 2 of the dialysis tubes were filled with approximately 10 grams of distilled water and 2 with salt water, then they were weighed on electronic scales and the weight was recorded. The dialysis tubing was placed in 4 smaller beakers, 2 containing salt water and 2 with distilled water, with rubber bands holding them in place. One saline tubing and one fresh tubing were placed in the beakers with salt solution and the remaining tubes were placed in the distilled water beakers. After 48 hours the dialysis tubes were weighed and compared to the original recordings to measure the rate of osmosis that occurred through the dialysis tubing.

The variables that occurred during the conduction of the osmosis practical examination and the limitations of these errors/variables.

Discussion

The aim of this experiment was to demonstrate the effect changes in environment have on osmosis through a semi permeable membrane. To demonstrate this, the different environments used were saline solution and distilled water to represent salt and fresh water environments. A dialysis tube was used to represent a semi-permeable membrane in which osmosis could occur through.

It was hypothesized that the distilled water would deluge into the beakers and dialysis tubes that contained the saline solutions of salt to dilute the solute due to osmoregulation. The results showed that the beakers and the dialysis tubes for each of the experiments lost weight. These results contradict the research performed prior to the conduction of this experiment.

However, these results are likely to be unreliable due to errors in the conduction of the experiment or unpredicted factors such as evaporation. This includes spillage of water onto the scales when measurements were taken, and water spilling out when the beakers were transported from the practical bench to another bench for examination. Also, when the dialysis tubes were being weighed, they had to be held up so that water would not spill out, and this could have resulted in weight from the hand holding the tubing to be measured also or the tube to be held up too high, resulting in less weight to be recorded.

This experiment could have been improved by carefully handling the beakers when they were being transported and when they were placed on the electronic scales to be weighed. When the dialysis tubing was being weighed the other end could have been tied off, eliminating the need for holding the dialysis tubing, and extra weight or less weight to be recorded. Another limitation to this experiment was the experiment could only be checked in the next biology theory class, and this meant that the length of time the experiment was left for could not be chosen. Also the amount of time was not measured or recorded. This could have been avoided by predicting the amount of time the experiment would be left for and measuring it with a stop watch.

Due to these limitations, the results of the experiment could have been tampered with during the process of the experiment. So although the results contradicted the hypothesis, it is likely that if the experiment was repeated, considering the adjustments mentioned, the results would be different.

Further research should be taken to see if the hypothesis is scientifically correct, and if other similar experiments did prove this hypothesis.

Conclusion

The aim, of this experiment was to test the effect changes on the environment has on osmosis through a semi-permeable membrane. It was hypothesized that the distilled water would deluge into the beakers and dialysis tubes that contain the saline solutions of salt to dilute the solute due to osmoregulation (Saladin, 2000). It was also predicted that when the solutions are isotonic, the weights would be recurring (Innovateus, 2006).

The experiment is considered unsuccessful as the results of this experiment proved the hypothesis wrong as all but one beaker lost weight. Also none of the weights were recurring for the isotonic solutions. This however could have been due to errors in the performance of the experiment. This is the most reasonable conclusion as to why the results didn’t confirm the research conducted.

For valid results, the experiment should be reconducted with the previous limitations taken into consideration. Also further research regarding similar experiments and the results those experiments concluded to compare them to the results of this experiment.