Experiment to investigate the effects of various sucrose solutions on potato.

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Experiment to investigate the effects of various sucrose solutions on potato.

Osmosis is defined as the net movement of water or any other solutions molecules from a region in which they are highly concentrated to a region in which they are less concentrated. This movement must take place across a semi-permeable membrane such as a cell        concentration i.e. in the solution; to a low concentration i.e. in the potato piece. Therefore, the potato pieces in a higher water concentration (low sucrose) will gain more mass through osmosis than those pieces in a higher sucrose concentration. however, at a point, in the concentration change,

I expect the potato to actually lose mass. This is

due to the fact that as the concentration of sucrose

in the solution increases, it will reach a point where

the potato and the solution are isotonic (the

concentration of sucrose in the solution equals that

of the concentration inside the potato) any higher

concentration of sucrose in the solution thereafter

will result in osmosis occurring in the opposite

direction; i.e. water molecules will be moving from a

higher concentration inside the potato, to a lower

concentration in the solution itself.

Further information

Plant cells have a strong cell wall constructed of

cellulose surrounding them. When cells take up water by osmosis, they begin to swell. If this were to happen to an animal cell, it would take up water until it simply bursts; however, this is prevented from happening in plant cells due to the strong cell wall which prevents this. Plant cells become “turgid” when they absorb large amounts of water. The ‘turgor’ pressure inside the cell gradually increases until the ‘hydrostatic’ pressure has grown to a point where no more water can enter the cell – it has become turgid. Turgidity is very important to plants, as it provides the rigidity needed in the leaves of the plant in order to keep then in position. If a plant was to do without water for an extended period, the turgor pressure would decrease, and the plant would wilt.

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     The same thing occurs when cells are placed in a concentrated

 sugar solution. Osmosis occurs in the opposite direction, and the

cells begin to lose water, and become ‘flaccid’. This is the exact

opposite of ‘turgid’, the contents of the cell shrinks, and pulls

 away from the cell wall. These cells are said to be called

‘plasmolysed’. When plant cells are placed in a solution which

has exactly the same concentration as the cells, they are in a state

called ‘incipient plasmolysis’, or isotonic.

Variables

To ensure a fair test, certain aspects ...

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