What is the concentration of the Cell Sap in a Potato?

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What is the concentration of the

cell sap

in a


        Preliminary investigation-

0.0 M

        Initial mass                   1.03 g

        Final mass                    1.09 g

        Change in mass         + 0.06 g

0.1 M

        Initial mass                    1.03 g

        Final mass                     1.06 g

        Change in mass          + 0.03 g

0.9 M

        Initial mass                    1.20 g

        Final mass                     1.14 g

        Change in mass          - 0.06 g

        Background knowledge-

        Water is essential to not only plants but all living things that need to carry out the 7 life cycles which are, movement, respiration, sensitivity, nutrition, excretion, reproduction and growth. Similarly, water is needed for photosynthesis to occur as it is stated in the formula;

Water + Carbon Dioxide  Oxygen + Glucose

        In this process the plant is able to make glucose with water and carbon dioxide. The formula will not work properly.

        Being able to transport water to all of the cells of the plant is vital. A plant has lots of thin tubes that carry liquids up and down the plant, they are called, the plants Transport System. Part of that system is the Phloem tube which carries glucose and the Xylem vessels need to carry water throughout the plant. Likewise, water keeps the plant cool and keeps the cells turgid giving it support so that it can get the most sun rays for photosynthesis to occur at a maximum.

        When the plant cells start to take up water by osmosis, they start to swell. They become turgid when they have a large amount of water stored in vacuole. They become hard due to the pressure increasing inside the cell as the vacuole is exerting turgor pressure, so that eventually the internal pressure of the cell is so high that no more water can enter the cell. The opposite of turgid is flaccid.  When plant cells are placed in concentrated sugar solutions they lose water by osmosis and as a result, they become flaccid as the cells are said to be plasmolysed. The cell is flaccid as there is no pressure on outwards from the cell.

        Diffusion is the movement of particles, in a liquid or a gas, from a high concentration to a low concentration. Osmosis is the diffusion of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. The definition of osmosis means that water can be shared through all the cells and distributed evenly to the vacuoles, where water and glucose are stored. Semi-permeable membranes, cell membranes, allow some things to pass through them but prevent other things from passing through. They allow through small molecules like Oxygen, water, Carbon Dioxide but not large molecules like Starch or Sucrose to pass through. The semi-permeable membrane is also known as the molecular sieve and it is the cell’s own membrane. The cell wall is fully permeable therefore letting through all molecules regardless of relative molecular size while the cell membrane is not fully permeable only allowing through smaller molecules.

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        Taylor wrote, in 1972, that osmotic potential is defined as, “the portion of the water potential that results from the combined effect of all solute species present in the soil or plant system.” A solution has a high osmotic potential if it has a high proportion of water molecules. Conversely, a solution has a low osmotic potential if it has a relatively low amount of water molecules and is therefore a concentrated solution. The solution with the highest osmotic potential is pure water. In an isotonic solution, the concentration of the solutions is the same inside the cell and outside the ...

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