Osmosis Flashcards
Define osmosis.
The passage of water from a region where it has a higher water potential to a region where it has a lower water potential through a selectively permeable membrane.
What is a solute?
Any substance that is dissolved in a solvent, for example, water. The solvent and solute form together to make a solution.
What is water potential?
The pressure created by water molecules, measured in pascals.
What is the water potential of pure water?
0
What does the addition of a solute do to water potential?
Lowers it.
How does water move by osmosis (include water potential in description)?
Water molecules diffuse from the side with the highest water potential to the side with the lower water potential, down a water potential gradient. They diffuse until both potential are equal.
How can you test the water potential of a cell?
Place a material in a series of solutions of different water potential, the one in which there was no change in mass has the same water potential.
Both the solute and water molecules are in … due to their kinetic energy.
Random motion.
What molecules does the selectively permeable membrane allow across?
a
What is established when water potential is equal at both sides?
A dynamic equilibrium.
What is the highest value of water potential?
0
What does incipient plasmolysis mean?
If water leaves the cell the protoplast stops pushing on the cell wall and at this stage it is said to be at incipient plasmolysis.
What does plasmolysed mean?
The condition of a cell caused by water loss that causes the protoplast to pull away from the cell wall and the cell to shrink.
explain what is meant by ‘selectively permeable’.
a
What are plant cells unable to control?
The composition of the fluid around their cells.
