How does the concentration of sucrose affect the weight of pieces of potato after osmosis has taken place?

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Biology SC1: How does the concentration of sucrose affect the weight of    pieces of potato after osmosis has taken place?

Aim

The aim of this is experiment is to investigate how much sucrose is in a potato. We are going to investigate the effect of different concentrations of sucrose on the weights of pieces of potato after osmosis has taken place.

Prediction

I predict that the less concentrated the solution of sucrose is, the greater the weight of the potato will be. I predict this because osmosis is the movement of water from a region of high water concentration to a region of low water concentration through a semi-permeable membrane i.e. the cell wall of the potato. If the concentration of water inside the potato is high then the water will pass out through the cell wall, decreasing the weight of the potato. If the concentration of water outside of the potato is high then the water from outside of the potato will pass through the cell wall into the potato, thus increasing the weight of the potato.  A low concentration of sucrose will have a greater ratio of water to sucrose, so more water will pass thorough into the potato in an attempt to even up the amounts of water and sucrose on both sides. If the  concentration of sucrose outside of the potato is high then there will be less water to pass through into the potato and the potato will therefore lose water from inside in an attempt to even up the concentrations of sucrose and water on both sides. If the cell has lost water then it will not weigh as much as a cell full of water as the cell will be flaccid. If the cell has gained water then it will be turgid and will weigh more. The higher the concentration of the sugar solution, the faster osmosis will take place. I think this because the more sugar in the water, the longer it will take for it to balance out.

Some background information

Osmosis is the movement of water from an area of high concentration (lots of water particles) to an area of low concentration (few water particles). It is only the movement of water, as only water particles are small enough to pass through the semi-permeable cell membrane of the plant. Osmosis makes plants cells swell up if they are surrounded by a weak solution i.e. a lot of water, and they therefore become turgid. This is useful in giving support for cells and opening stomatal guard cells. If a cell is placed in a concentrated solution i.e. not a lot of water, then the cell will lose water in an attempt to even up the concentrations on either side of the cell membrane. The cell will then begin to shrivel up and become flaccid (floppy). There is always a steady flow from the weaker solution to the stronger solution, which is why we will leave the experiment for a few days to make sure that all the water that will pass through has passed thorough. The water particles also act as though they are trying to dilute the stronger solution and therefore even up the concentrations on either side of the membrane.

Some membranes in plant cells, such as in a potato, allow certain particles to pass through them and not others. They are selectively permeable. The diffusion of water through a selectively permeable membrane is called osmosis. The rate at which osmosis takes place is affected by the concentration of water in the two solutions on each side of the membrane. If a selectively permeable membrane separates the two solutions, water moves through it in both directions at the same time. However, more water leaves a dilute solution (high water concentration) and passes into a more concentrated solution (low water concentration) than enters it. Although the water appears to move across the membrane in one direction, it is in fact moving in both directions but more one way than the other.

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When the concentration of water is the same on both sides of the membrane, the movement of water will be the same in both directions. At this point, the net exchange of water is zero and the system is in equilibrium.

 

                                                                       

This information is relevant to the experiment we are doing because we are investigating osmosis and how different molar concentrations ...

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