Estimate the concentration of the cytoplasm of potato cells Essay Example
Estimate the concentration of the cytoplasm of potato cells Essay Example

Estimate the concentration of the cytoplasm of potato cells Essay Example

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  • Pages: 5 (1171 words)
  • Published: September 27, 2017
  • Type: Essay
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The investigation which I am going to be carrying out is to estimate the concentration of the cytoplasm of potato cells. I will do this by investigating using the movement in and out of the potato cells through Osmosis.

Osmosis is the process whereby water molecules pass through a semi-permeable membrane from a high concentration to a low concentration until an Osmotic equilibrium is reached. So it is like a special form of diffusion. Plants take up water from the soil, through their root hair cells by the process of Osmosis, and they continue to use Osmosis from cell to cell to transport water up the plant.

Plants have many uses for the water they take up by Osmosis, one main importance being to maintain the plants structure by keeping them upright and turgid. As i

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n plant cells, they have a special containment area for water called the vacuole, when the vacuole is void of water, the cell will become flaccid and loses its shape. When enough water has been lost the cell will begin to retract and pull away from the cell wall. When this occurs the cell has been plasmolysed. However when a plant has a good water source the vacuole will take up large quantities of water and become turgid.

This turgidity is essential for plants as it is this that plants rely on to keep them upright and maintain their structure, this is where the plants unique traits of having a cell wall help the cell to avoid from rupturing, as the cell wall which is a cellulose based structure is extremely strong and can provide enough resistance to hold the cell together. A

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the cell becomes turgid and pushes outwards, the cell wall pushes back with an equal opposing force. This is why animal cells are not well adapted to take up water, as they have no place like the vacuole to store it as plant cells do, and they have no cell walls, so when they take up to large a quantity of water, they will rupture.

Plants also use water for the all important process of photosynthesis, where the plant will combine the two reactants, carbon dioxide and water to produce oxygen and glucose, this reaction is vital to our way of life, as without plants photosynthesizing, all oxygen breathing creatures would be starved of oxygen and suffocate also the entire food chain would collapse as the producers which start it off will not be producing their own food source anymore.

The final use of water for plants is in transpiration in order to cool the plant down and release excess water in order to maintain the diffusion gradient, otherwise excess water would build up, increasing pressure and possibly damaging the cells.

Variables

In my investigation there will be many variables that I must try and maintain and keep at a constant level, otherwise my results may come out with anomalies and other errors. Below I have listed some variables, how they will affect my work and what I will do to try and solve this problem.

Surface Area: If the surface areas of the potato chips are different, then some potatoes will have an unfair advantage over others, as with a larger surface area there is an increased rate at which water will be taken up. So to try and

increase my results accuracy I must try and keep the surface area as similar as possible

Concentration of Solution: In Osmosis there is the rule that the water transfer must be moving from a high concentration to a low concentration, so I believe that with the concentration will changed the time in which the chip will take in order to achieve Osmotic equilibrium will also change. This is the factor that I will vary so as to discover the concentration of the cytoplasm in potato cells, and is the basis of my investigation.

Temperature: This is important as it affects the amount of energy that the water molecules will have, and if they have different levels of excitation, as when this occurs the plant cells will move faster then the Osmosis may occur at different rates, the temperature may also affect the rate at which the water evaporates, lowering the level of water in which the chips are immersed, and increasing the concentration of the water which the chips are immersed in. So I must try and maintain the same temperature throughout all my experiments.

Pressure: Pressure is quite an important variable; as if there is a change in the external pressure my results will be drastically changed. If it were changed to a low external pressure, then there would be a high level of water loss from the cell and vice versa. So I must ensure that the pressure is kept constant otherwise it may alter the water-flow.

Time of Exposure: The time of exposure is also very important, as I must make it long enough for the cells to reach an Osmotic equilibrium, I also must ensure

that all of the chips get the same time of exposure to the solutions. So I will try and remove all chips and place them all in at the same time.

Prediction

I predict that in a concentrated solution where there is little water present, that there will be a nett loss of water from the cells. In a more dilute solution, where there is more water present I predict that there will be a nett gain of water.

Preliminary Experiment

The reason that I conducted a preliminary investigation was so that I could find out the best method in which I should conduct my main experiment and to see whether or not the concentration of the solutions really does affect the rate of Osmosis in potato cells. This trial run also helped me to explore the variables that may affect my experiment in order to change these when I redo my experiment and this time use the knowledge I have acquired to set up a fair test in order to obtain a valid set of results. This is how I conducted my experiment.

Apparatus

- 7 Petri dishes

- 1 scalpel

- 1 white ceramic tile

- 7 concentrations of salt solutions

- 1 ruler

Preliminary Method

First of all we sliced the potato chips into quite fine 5cm long strips, with the scalpel on the ceramic tile in an attempt to try and increase the accuracy. We then poured a small amount of the seven concentrations into each of the uncovered Petri dishes. We then placed the chips in one at a time for 15 minutes; we hoped that this would be enough time for the potato cells to reach osmotic equilibrium with the salt

solution. Afterward we removed the chips from the solutions and measured the potato chips length and below are our results.

I predicted that there will be an increase in length of the potato chips in the salt solutions of lower concentration, as the concentration of the solution rises the change in length of the potato chips will decrease.

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