Determining the Concentration of the Cell Sap in Potato Storage Tissue

Determining the Concentration of the Cell Sap in Potato Storage Tissue

Aim: To determine the concentration of the cell sap in potato storage

tissue. By using Osmosis, determine what the sugar concentration of

cell sap is.

Prediction

I predict that the potato segment in the distilled water will

definitely gain in weight because the solution outside it has a much

higher concentration of water then in the cell sap meaning Osmosis

will occur and the potato segment take in water. I predict that 0.2M

sugar solution will also gain weight because it still has quite a high

concentration of water outside the potato. The potato in the 0.4M

solution will gain weight but the potato in the 0.6M and 0.8M

solutions will lose weight. The glucose concentration of the cell sap

will be between 0.4M and 0.5M.

Scientific Knowledge

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This experiment is based on the concept of Osmosis. Osmosis is the

diffusion of water molecules from a region of high water concentration

to a low water concentration through a semi permeable membrane (in

this case, the cell potato cell membrane). The cell walls of the

potato cells are semi permeable meaning that water molecules (which

are small) can fit through but other bigger molecules such as glucose

cannot pass through. The water molecules can flow both ways through

the membrane, letting molecules both in and out.

The Kinetic theory states that all molecules of every substance have

energy which causes them to move about for example a chemical reaction

can be accelerated through heating because the molecules gain more

energy efficiently causing harder and more effective collisions of the

molecules. In water the molecules have energy which makes them move,

it is this energy which powers Osmosis and allows water molecules to

pass through the semi permeable membrane.

The experiment uses Osmosis to make an estimation of the concentration

of the cell sap in the potato storage tissue. The cell sap is a

solution mainly of water, sugar, starch and salts.