Investigating the process of Osmosis

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Sophie Keltie 11JK

Biology Coursework

PLANNING

In my experiment I will be investigating the process of osmosis and using this information to help me identify the concentration of the cytoplasm of potato cells.

Osmosis is the term that describes the diffusion of water in plant cells. Osmosis allows processes such as transpiration to take place and is the way that water can move in and out of cells. It is important in plants as the water is diffused from the soil to the root hairs. Osmosis refers to the net transfer of water through a semi-permeable membrane, from a high water concentration to a low water concentration. The semi-permeable membrane only allows the movement of smaller particles, such as water; bigger particles such as sucrose or salts are too large to pass through.

HIGH water concentration                                                      LOW water concentration

                                                   Net movement of water             LOW water potential        

HIGH water potential

 

LOW solute concentration                                                    HIGH solute concentration

This movement of water continues until the concentration of water is the same on both sides of the membrane, and the movement of water will be the same in either direction, meaning the net exchange of water will be zero. This refers to a solution’s water potential. A dilute solution will have a higher water potential than a more concentrated solution as more water will flow from the dilute solution to another more concentrated solution, e.g. pure water, which has a water potential of 0.

Using this research on osmosis, I will be able to determine the concentration of the potato cytoplasm by the process of osmosis. If water particles have diffused into the potato chip, then the mass will increase. This is because the water molecules will have diffused from where there is less to more water molecules, or, from a high water potential area to a low water potential area.

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For my experiment I will use the following: raw potato chips, sucrose solutions of varying concentrations, boiling tubes, balance, drying tissue, knife and cutting board. We will use this tissue to dry off any liquid, and the cutting tile to ensure safety, and make it more convenient to clean. Using a scientific balance will help us to precisely measure the chip weights.

Firstly, we will cut several potato chips of similar size. Because we will use three chips in each concentration, for accuracy, we will need to distinguish between the chips to weigh them. To do this, we ...

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