Flashcards in 2.6 Deck (18):
What is osmosis?
The passage of water molecules from an area of higher water potential to an area of lower water potential through a partially permeable membrane
What is the water potential of pure water at 25 degrees and 100kPa?
What effect will adding a solute have on the water potential of a solution?
Lowers water potential
Why does adding a solute lower the water potential?
The solute molecules impede the movement of water molecules, reducing the number of collisions the water makes with the membrane.
Therefore, the solution exerts less pressure on the membrane and has a lower water potential
What is the water potential of any solution?
Less than zero
Is osmosis a passive or active process?
What happens to the net movement of water molecules when the water potentials are the same on either side of the membrane?
No net movement of water molecules
A dynamic equilibrium is established
What happens when an erythrocyte is placed in pure water?
Water moves into the cytoplasm of the cell, which contains solutes, down a water potential gradient
This exerts a higher pressure on the cell surface membrane of the erythrocytes so membrane ruptures
This is called haemolysis (cytolysis)
What happens when an erythrocyte is placed in a solution of concentrated solute?
Water moves down a water potential gradient from the cytoplasm to the solution.
Pressure exerted on cell surface membrane is reduced.
The cell shrinks and shrivels (has been crenated)
Why must the water potential of the blood be regulated?
Blood contains solution and electrolytes.
As the concentrations of these increase in cells, the water potential of the plasma will decrease
Must be regulated to prevent loss of water from cells
What is a vacuole?
Fluid-filled space inside the cytoplasm, containing salts and sugars etc.
What is the protoplast?
Made up from the cell surface membrane, cytoplasm, tonoplast
What is the tonoplast?
The membrane around the vacuole
What is the cell wall in plants made from?
What is cellulose?
What are properties of cellulose?
How does a plant become turgid?
When water enters, the protoplast exerts pressure on cell wall, which resists the pressure