Biology Module 1 - 3.membrane structure and function 3.3 investigate the effects on plant cells of immersion into solutions of different water potentials

3.3 investigate the effects on plant cells of immersion into solutions of different water potentials



high water potential outside and low water potential inside plant cell

• there is osmotic uptake of water where water diffuses into the cell through the partially permeable membrane

• cell contents expands and pressure of the cell content increase and push out on the cell wall

• the pressure of the cell wall resist water uptake by pushing back on the cell content making the cell turgid

• eventually there is no uptake of water because the cell potential outside equal the cell potential inside so the cell becomes fully turgid as it has reached equilibrium.

NB plant cell does not burst as cell wall prevents this

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low water potential inside and high water potential outside plant cell

• there is osmotic loss of water where water diffuses out of the cell through the partially permeable membrane

• the cell becomes flaccid as water diffuses out and the contents do not push out on the cell wall

• as water continuously diffuses out of the cell it becomes plasmolysed where the plasma membrane pulls away from the cell wall in some places. The external solution fills the gap between the cell wall and the plasma membrane.

• some parts of the membrane will not pull away from the cell but if they do then the cells die