An Investigation Into the Effect of Sucrose Concentration on Osmosis

An Investigation Into the Effect of Sucrose Concentration on Osmosis

AIM:

The aim of my experiment is to investigate the effect of sucrose

solution on osmosis in potato cells, and what the point of equilibrium

would be. I shall be observing how the mass of the potato chip changes

in five different concentrations of glucose solutions.

HYPOTHESIS:

Osmosis is the diffusion of water molecules from a high water

potential to a lower water potential through a partially permeable

membrane. A partially permeable membrane, such as a cell wall, allows

small molecules, such as water molecules, pass through it, but does

not let bigger molecules such as sucrose through it.

Cells placed in distilled water take up water by osmosis. This

happens because the cell contains dissolved chemicals and therefore

has a lower water potential than the distilled water surrounding it.

As there are more water molecules outside the cell, more go in to the

cell than out of it. The net movement of the water molecules is into

the cell, and the cell will increase in mass. Eventually the cell

stops taking up water, even though the concentrations inside and

outside are not even. This is because the cell wall becomes stretched

and prevents any more water entering. The cell is said to be turgid.

Cells placed in a concentrated sugar solution lose water by osmosis,

as the water potential is higher inside the cell. As there are more

water molecules inside the cell, more water molecules leave the cell

than enter it. The net movement of the water molecules is out of the

cell. This causes the cell to become flaccid, and for it to decrease

in mass.

When a cell is placed in a concentration of sugar solution that has

the same water potential as the cell sap, an equal amount of water

molecules go in and out of the cell. There is no net movement of water

molecules and the mass of the cell will stay the same. This is called

the state of equilibrium.