Question 5a
Describe what will happen if a plant cell is placed in a solution that has a higher water potential than the cell.
Make use of these terms when constructing your answer:
cytoplasm, water potential, turgid, osmosis, protoplast, equilibrium, cell wall, freely permeable, partially permeable, cell surface membrane, vacuole, tonoplast.
Context:
- When a plant cell is placed in a solution with a higher water potential, it means the surrounding solution is more dilute (has more free water molecules) compared to the cell’s internal environment.
Process and Outcome:
Eventually, equilibrium is reached, where the influx of water stops as the internal and external water potentials balance out.
Osmosis:
Osmosis is the movement of water from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
In this case, water moves from the solution (higher water potential) into the plant cell (lower water potential) through the cell surface membrane.
Pathway of Water:
Water enters the cytoplasm and vacuole through the tonoplast (membrane surrounding the vacuole).
Effect on Protoplast:
As water enters, the protoplast (living part of the cell within the cell wall) expands and presses against the cell wall.
The cell wall is freely permeable, allowing water to reach the cell’s interior easily.
Turgidity and Equilibrium:
The cell becomes turgid as the pressure increases within the cell due to water influx.
Turgor pressure builds up, pressing the protoplast against the cell wall, which limits further expansion.