The Effects of Osmosis

GCSE Biology Coursework

Effects of solution on plant cells.

If we put plants in a hypertonic solution will undergo plasmolysis, a condition where the plasma membrane pulls away from the cell wall as the cell shrinks. The cell wall is rigid and does not shrink. Animal cells placed in a hypertonic solution will undergo crenation, a condition where the cell shrivels up as it loses water. In my experiment

I’m going to use a potato.

Plan:

Aim

Independent variables

Dependent variable and factors which I can control in my experiment

Equipment

Method

Prediction

Theory

Results

Analysing evidence

Evaluation

Aim

In my experiment I’m going to find out how the sodium chloride solution affects the potato chips.

Equipment:

Stop-Clock

Cork borers

250ml beakers

Measuring cylinders

Ruler

Potato cylinder, 5cm in length

Sodium chloride

Distilled water

Method:

The first thing I’m going to do is to cut five special potato cylinder shape pieces for each experiment. I’m going to take a cork borer and make five equal potato cylinders.

Each potato cylinder will be 5cm long. I also need to make sure, that all these pieces have the same size and mass. Then, I’m going to dry them on paper. After I finish this procedure, I’m going to weigh all these cylinders and record its first weight, by putting them on the special electronic scales. After I’ve done this, I’m going to put them into the beakers with NaCl and of them into the distilled water solutions and let the reaction start off. After 30minutes I’m going to take them out, dry for 10 seconds and weigh, comparing the new results. As I said in my prediction, the potato chips increased in their size (probably), and increased in their weight.

Then I’m going to put them into the different cylinders with different NaCl solutions, there will be five cylinders with NaCl solution and one, containing distilled water. The amount of the liquid I’m going to pure will be 150ml in all beakers. The concentration of the glucose solution is going to be: 0.20, 0.40, 0.60, 0, 80 and 1.00 mol. respectively.

As the glucose concentration increases, mass of potato chips decreases. I starts happening when the concentration of glucose becomes 25 M. As the concentration of glucose decreases, mass of potato chips increases. The potato sticks are going to expand in distilled water, because water molecules can go through a special permeable membrane, which can be found in the plant cells.

When you put an animal or plant cell into liquid containing water one of three things will happen.

• If the medium surrounding the cell has a higher water concentration than the cell (a very dilute solution) the cell will gain water by osmosis.
  
  Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. The net (overall) result is that water enters the cell. The cell is likely to swell up.
• If the medium is exactly the same water concentration as the cell there will be no net movement of water across the cell membrane.
  
  Water crosses the cell membrane in both directions, but the amount going in is the same as the amount going out, so there is no overall movement of water. The cell will stay the same size.
• If the medium has a lower concentration of water than the cell (a very concentrated solution) the cell will lose water by osmosis.
  
  Again, water crosses the cell membrane in both directions, but this time more water leaves the cell than enters it. Therefore the cell will shrink.

Theory

The Effects of Osmosis

When an animal cell or a plant cell is placed in a medium, which is a water solution, the possible consequences are listed below.

• If the water concentration cytoplasm in the cells is lower then that of the medium surrounding the cell then osmosis will result in the cell gaining water. The water molecules are free to pass across the cell membrane in both directions, but more water molecules will enter the cell than will diffuse out with the result that water enters the cell, which will then swell up and could possibly burst.
• If the water concentration inside the cell is the same as that in the surrounding medium (i.e. the medium is a isotonic solution) there will exist a dynamic equilibrium between the number of molecules of water entering and leaving the cell and so the cell will retain its original size.

• If the water concentration inside the cell is higher then that of the medium the number of water molecules diffusing out will be more than that entering and the cell will shrink and shrivel due to osmosis.

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