Investigating osmosis
Aim:
I am going to investigate the mean water potential of potato cells to the point of equilibrium by putting pieces of potato into different concentrations of sucrose solution and recording the change in mass.
Prediction:
I predict that potatoes immersed in solutions with a water potential lower than (i.e. more concentrated) that of the potato cells, will decrease I mass after being left for a period of time. The potatoes will decrease in mass as water has moved out of the cells through a partially permeable membrane by osmosis. The potato will become flaccid and is said to be plasmolysed.
Potato immersed in solutions with higher water potential than that of the cells (i.e. more dilute) will increase in mass (after being left for a period of time) because water has moved into the cell through a partially permeable membrane by osmosis. The potato will become turgid.
There will be a point where there is no change in mass. This is where the water potential is equal on each side of the partially permeable membrane. This does not, however, mean that the water ceases to pass through the partially permeable membrane; it simply means that the net amount of water movement equals 0 therefore solutions are in equilibrium. Above this point, the pieces of potato will have lower water potential than the sucrose solutions and will take up water, therefore increasing in mass. Below the point of equilibrium, the pieces of potato will have a higher water potential than that of the sucrose solution cells and will lose water, therefore decreasing in mass.
Aim:
I am going to investigate the mean water potential of potato cells to the point of equilibrium by putting pieces of potato into different concentrations of sucrose solution and recording the change in mass.
Prediction:
I predict that potatoes immersed in solutions with a water potential lower than (i.e. more concentrated) that of the potato cells, will decrease I mass after being left for a period of time. The potatoes will decrease in mass as water has moved out of the cells through a partially permeable membrane by osmosis. The potato will become flaccid and is said to be plasmolysed.
Potato immersed in solutions with higher water potential than that of the cells (i.e. more dilute) will increase in mass (after being left for a period of time) because water has moved into the cell through a partially permeable membrane by osmosis. The potato will become turgid.
There will be a point where there is no change in mass. This is where the water potential is equal on each side of the partially permeable membrane. This does not, however, mean that the water ceases to pass through the partially permeable membrane; it simply means that the net amount of water movement equals 0 therefore solutions are in equilibrium. Above this point, the pieces of potato will have lower water potential than the sucrose solutions and will take up water, therefore increasing in mass. Below the point of equilibrium, the pieces of potato will have a higher water potential than that of the sucrose solution cells and will lose water, therefore decreasing in mass.
