Science Experiment Report Osmosis Essay
Osmosis in potato cells Aim: To view and examine the effect different concentrations of sucrose solution has on the movement of water across the cell membrane. Hypothesis: That the potatoes will either increase or decrease in mass, due to the effect of the different concentrations. Osmosis will occur. Apparatus: * Fresh potatoes * Apple corer * Scalpel * Petri dishes X 10 * 50ml measuring cylinder * Distilled water * Paper towelling * Sucrose solutions: * 1. 0M * 0. 8M * 0. 6M * 0. 4M * 0. 2M Method: Day 1 1. A cylinder was poked out of the potato with the apple corer and removed from the corer.
That cylinder was then trimmed to make sure no skin was left. 2. The cylinder was sliced into 1mm thick pieces producing small cylinders. This was repeated until 20 pieces were obtained. 3. The 20 slices were placed into petri dishes and then weighed. The weights were recorded. This mass was known as the initial mass. (refer to results) 4. The different concentration of sucrose was then added into one petri dish, so in total there were 5 petri dishes with different concentration molars of sucrose, each containing the 20 slices of potato.
The petri dish was then covered and left to leave overnight in room temperature. Day 2 1. The water was soaked up from the petri dish gently by using the paper towel. This was meant to be done gently enough to not press hard on the potatoes. 2. The potato slices were weighed again and the results were recorded. This mass was known as the final mass. 3. The changes in mass of the initial and final mass were recorded and are displayed in the results section. 4. The results from the different members doing the other concentrations were combined. Results: Sucrose solution (M)| initial (g)| after(g)|
0. 2| 2. 653| 2. 812| 0. 4| 3. 61| 2. 906| 0. 6| 3. 443| 2. 836| 0. 8| 2. 363| 3. 129| 1| 4. 517| 3. 713| Table 1: Table showing the different concentrations of sucrose added to the potatoes that affected their weight Graph 1: Showing data of the results in a graph Graph 2: Showing the percentage of loss or gain after the initial mass was subtracted from the final mass Table 2: Therefore in summary Concentration of sucrose| Loss or gain %| Gain or loss in mass of potatoes| Type of osmosis that has occurred| 0. 2M| 6| Gain| Hypotonic| 0. 4M| -19. 5| Loss| Hypertonic| 0.
6M| -21. 4| Loss| Hypertonic| 0. 8M| 24. 5| Gain | Hypotonic| 1M| -21. 7| Loss | Hypertonic| Discussion: The aim of this experiment was to view and examine the effect different concentrations of sucrose solution can have on the movement of water across the cell membrane. The concentration of particles along a concentration gradient is called diffusion. Along a concentration gradient means that it is moving from an area of high to low concentration. Diffusion is a naturally occurring process which requires no energy input therefore is called a passive transport (process).
For example if a fluid is poured in a container of another fluid it will gradually disperse itself throughout the container. In the case of any solid crystals being added to water, they will move around the container until there particles are evenly distributed. Alongside diffusion other names given to the movement of materials through the cell membrane are: * Facilitated diffusion * Again no energy is used by this transport since the particles are moving along the concentration gradient. In addition this form of transport requires the assistance of specific protein molecules embedded in the cell membrane.
* Active transport * Energy is used by this transport since the particles are moving against the concentration gradient so from an area of low to high concentration. This form of transport also requires the help of protein channels. * Exocytosis * Energy is used in the transport process since particles are moving against the concentration gradient. Molecules are transported out of cell vesicles fusing with the membrane. * Endocytosis * Energy is used in the transport process since particles are moving against the concentration gradient. Molecules are transported into the cell by vesicles fusing with the membrane.
In our experiment we looked at the diffusion form of transport. The net movement of water molecules, across a semi-permeable membrane, from an area of high to low concentration of water is called Osmosis. Therefore seeing as we used sucrose solutions in our experiment the process of osmosis was observed. The first day of the experiment involved the preparation of the potato slices in the petri dishes. They were then weighed and only then were the sucrose solution added on to the potatoes. The potatoes in the sucrose solutions were left overnight to remark the changes to the overall mass of the potatoes.
Everyone used one different concentration of sucrose solutions, they were: 0. 2, 0. 4, 0. 6, 0. 8 and 1 molar. The weight of the potatoes is recorded as initial mass on table 1. The second day of the experiment was the day to observe the transportation involved in the modifications of the mass of potato. The effects that the concentrations of sucrose had on the potato slices were different in all solutions. Some increased and some decreased in overall mass. This increase and decrease observed is known to be identified as stated before as being hypotonic (increase of solute particles) and hypertonic (decrease in solute particles).
The solutions that had hypotonic results were 0. 2 M and 0. 8 M, meaning that there overall mass had increased. The solutions that had hypertonic results were 0. 4 M, 0. 6 M and 1 M; they were the ones that had decreased in solute particles. For the Hypotonic solutions the sucrose solution moved into the potato cells swelling up the potato. The shrinkage or swelling of the potato slices were not visible, they were only obvious after the calculation of their loss or gain of weight percentages. Osmosis describes the movement of solute from low to high concentration.
r potential (high solute) A passive process More solvent enter High water potential( low) to lower wat To reach an equilibrium Conclusion: In conclusion the aim of this experiment was met where the effects of the different concentrations of sucrose solutions had varying results in the change of mass. 0. 2 and 0. 8 molars showed an increase in their overall mass whereas the rest of the solutions had a loss in mass. The solvent particles therefore were higher in concentration than the solute in solutions that