Finding the Water Potential of Potato Cells

Finding the Water Potential of Potato Cells

Aim: Our aim was to discover the water potential of potatoes cells

using different concentrations of sucrose solution

Science:

Osmosis is 'the movement of water molecules from a region of higher

water potential to a region of lower water potential through a

semi-permeable membrane'

www.s-cool.co.uk

'Water can move between cells (unligninified) freely as the cell walls

are permeable. However its movement is controlled by a number of

factors, which are given names; solute potential ([IMAGE]), Pressure

potential (+ Matrix potential =0 normally)([IMAGE]) and water

potential ([IMAGE]).

Solute potential ([IMAGE]): this refers to the amount of substance

dissolved in the cytoplasm. This effects water movement because water

always moves from a less concentrated medium to a more concentrated

medium.

Pressure potential ([IMAGE]): this refers to the pressure exerted by

the cell walls. In a plant, the cell will fill with water until the

inner membrane is pushing on the outer membrane to the same force as

the wall is pushing back; they then are equal forces and cancel out.

Therefore there is no more movement of water.

Water potential ([IMAGE]): this is a figure worked out from the

equation; water potential = solute potential + pressure potential ([IMAGE]).

The figure represents the tendency of a cell to give out water.

http://www.restoringearth.co.uk/site/ossmosis.htm

Water moving out of cells causes them to lose turgor pressure - cell

membrane detaches from cell wall and shrinks (wilting) - plasmolysis

Water moving into cells causes them to become turgid, swollen -

deplasmolysis

http://biomicro.sdstate.edu/Hutchesh/bio101/Graphics/lab4/tsld011.htm

The is a dilute solution inside the potato cells due to it's cell sap,

this is a 'Dilute fluid found in the large central vacuole of many

plant cells. It is made up of water, amino acids, glucose, and salts.

The sap has many functions, including storage of useful materials, and

provides mechanical support for non-woody plants'

http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0029874.html

Prediction: From the research I have done into osmosis I have been

able to make some predictions about the results I will get.