Osmosis and Water Potential

Question 1

movement of water controlled by 3 processes

Answer 1

bulk flow
diffusion
osmosis

Question 2

bulk flow

Answer 2

molecules of water move in mass from one place to another in response to differences in potential energy

Question 3

diffusion

Answer 3

spontaneous movement of water down a concentration gradient

Question 4

osmosis

Answer 4

movement of water or any solvent across a selectively permeable membrane
- water movement across plasma membrane facilitated by aquaporins
- Water flows spontaneously from region of lower solute conc (higher water conc) to a region of higher solute conc (lower water conc)
- hypotonic, isotonic, hypertonic

Question 5

hypotonic

Answer 5

solution surrounding cell has lower conc of solutes
- water moves into cell, cell wall prevents cell rupture; ideal for plant
- water potential -ve

Question 6

isotonic

Answer 6

solution surrounding cell has same conc of solutes
- water at equilibrium but cell is not turgid
- water potential = 0

Question 7

hypertonic

Answer 7

solution surrounding cell has higher conc of solutes
- water flow out of cells and plasma mebrane shrinks away from wall (plasmolysis), symplastic transport impaired; unusual in nature
- water potential = +ve

Question 8

water potential (Psi w)

Answer 8

measurement that predicts which way water will flow

water potential = osmotic potential + pressure potential (turgor pressure)

osmotic potential always <0
pressure potential always >0

water potential becomes more -ve as water moves up from soil to leaves

Question 9

pressure potential

Answer 9

based on mechanical pressure:
- as water enters vacuole, pressure against wall (pressure potential) increases
- cell wall counters internal pressure