Osmosis: Plant Cells Flashcards
Osmosis is the
net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
If a plant cell is placed in pure water or a dilute solution, ………..
water will enter the plant cell through its partially permeable cell surface membrane by osmosis, as the pure water or dilute solution has a higher water potential than the plant cell
As water enters the vacuole of the plant cell, …………..
the expanding protoplast does what
volume of the plant cell increases
The expanding protoplast (living part of the cell inside the cell wall) pushes against the cell wall and pressure builds up inside the cell – the inelastic cell wall prevents the cell from bursting
The pressure created by the cell wall also stops
too much water entering and this also helps to prevent the cell from bursting
When a plant cell is fully inflated with water and has become rigid and firm, it is ……
and why is this form good
When a plant cell is fully inflated with water and has become rigid and firm, it is described as fully turgid
This turgidity is important for plants as the effect of all the cells in a plant being firm is to provide support and strength for the plant – making the plant stand upright with its leaves held out to catch sunlight
What happens if a plant doesn’t get enough water
If plants do not receive enough water the cells cannot remain rigid and firm (turgid) and the plant wilts
Wilting is the loss of rigidity of non-woody parts of plants. as a result of diminished water in the cells.
If a plant cell is placed in a solution with a lower water potential than the plant cell (such as a concentrated sucrose solution), water will l
water will leave the plant cell through its partially permeable cell surface membrane by osmosis
As water leaves the vacuole of the plant cell, the volume
of the plant cell decrease
As water leaves the plat the protoplast
what happens
and what state does it become
gradually shrinks and no longer exerts pressure on the cell wall
As the protoplast continues to shrink, it begins to pull away from the cell wall
This process is known as plasmolysis – the plant cell is plasmolysed
Remember – plant cell membranes are composed of a phospholipid bilayer and are partially permeable (only certain molecules can cross), whereas plant cell walls are made of cellulose and are freely permeable. Thus, in a plasmolysed cell, the external solution will be exerting pressure on the protoplast, that is, there is not an empty space between the cell wall and protoplast.Pure water has a water potential of 0 kPa, so all other solutions will have negative water potentials.
