Investigating Osmosis in Potato Cells

Investigating Osmosis in Potato Cells

Planning:

Aim:-

To investigate the effect of different concentrations of sucrose

solution, on potato cells

Osmosis:-

Osmosis is the passage of high water concentration through a

semi-permeable membrane to a region of low water concentration, i.e.

the passage of water.

Explanation of osmosis

For osmosis to occur there must be;

semi-permeable membranes are very thin layers of material (cell

membranes are semi-permeable) which allow some things to pass through

them but prevent other things from passing through. Cell membranes

will allow small molecules like Oxygen, water, Carbon Dioxide, etc. to

pass through. Cell membranes will not allow larger molecules like

Sucrose, etc. to pass through.

Regions of high concentrated water are either a very dilute solution

of something like sucrose or pure water. In each case there is a lot

of water, there is a high concentration of water.

Regions of low concentrated water are a concentrated solution of

something like sucrose. In this case there is much less water.

If the solution surrounding the cell has a higher water concentration

than the cell, the cell will gain water by osmosis. Water molecules

are free to pass across the cell membrane in both directions, but more

water will come into the cell than will leave. The cell is likely to

swell up and become 'turgid'.

If the solution is exactly the same water concentration as the cell

there will be no movement of water across the cell membrane. Water

crosses the cell membrane in both directions, but the amount going in

is the same as the amount going out. The cell will stay the same size.

If the solution has a lower concentration of water than the cell the

cell will lose water by osmosis. Again, water crosses the cell

membrane in both directions, but this time more water leaves the cell

than enters it. Therefore the cell will shrink and become 'flaccid'

Potato plant cells:-

Plant cells always have a strong cell wall covering them.