osmosis/water potential Flashcards
what is osmosis?
net movement of water molecules from a solution of high water potential to low water potential across a partially permeable membrane
what is water potential?
a measure of the tendency for water molecules to move from one place to another
what is the symbol of water potential?
Ψ (Greek psi)
what are the units of water potential?
pascals (P)
what is the highest water potential possible?
0 = pure DISTILLED water
what happens to the water potential when solutes are added?
it lowers because the solution is more concentrated
what is solute potential?
the amount by which solute molecules lower the water potential
why does osmosis occur faster when water molecules move into a solution of low water potential?
steeper water potential gradient
what is a hypotonic solution?
the solution outside has a lower solute concentration (higher water potential)`
what is a hypertonic solution?
the solution outside has a higher solute concentration (lower water potential)
what is an isotonic solution?
water potential is equal to water potential of cells (important for homeostasis)
what happens to a plant cell in a hypotonic solution?
- higher water potential outside cell
- water enters cell by osmosis
- protoplast swells and presses against cell wall
- fully turgid (pressure of water resists entry of further water)`
what happens to a red blood cell in a hypotonic solution?
- cell gains water by osmosis
- swells and burst (due to thin cell membrane)
- this is called HAEMOLYSIS
what liquid do red blood cells live in to prevent haemolysis?
- blood plasma
- which has same water potential as red blood cells
what happens to a plant cell in an isotonic solution?
- equal water potential
- no water movement
- protoplast begins to pull away from cell wall
- this is called INCIPIENT PLASMOLYSIS
