2.1.5 osmosis

Question 1

define osmosis

Answer 1

the net movement of particles from a higher water potential to a lower water potential across a partially permeable membrane

Question 2

what is water potential

Answer 2

the tendency for water particles to move from one place to another
measured in kPa with unit psi
always negative; higher WP is pure water with value of 0kPa

Question 3

what effect does increasing the solute in a solution have on the water potential

Answer 3

more solute = lower water potential
water mols cluster around the solute + no longer able to move
exert less pressure on membrane or container

Question 4

what factors affect the rate of osmosis

Answer 4

water potential gradient = steeper gradient means faster rate of osmosis; more negative WP
surface area = larger area for osmosis to take place
thickness of membrane = thinner membrane means shorter distance to travel; faster rate

Question 5

what is a hypotonic solution

Answer 5

a solution with a higher water potential than inside the cell

Question 6

what is an isotonic solution

Answer 6

a solution with the same water potential as inside the cell

Question 7

what is a hypertonic solution

Answer 7

a solution with a lower water potential than inside the cell

Question 8

what effect do hypotonic solutions have on cells

Answer 8

water moves into cell by osmosis; causes them to swell
animal cell - cytolysis; increases pressure inside cell until cell mem bursts
plant cell - turgid; water enters vacuole and presses on cell wall; doesn’t burst

Question 9

what effect do isotonic solutions have on cells?

Answer 9

there will be no effect; no water enters or exits by osmosis; particles at equilibrium; no net movement since WP is the same

Question 10

what effect do hypertonic solutions have on cells?

Answer 10

water will exit the cell by osmosis causing them to shrink
animal cell - cells will crenate and lose their shape
plant cell - becomes flaccid and plasmolysed; water exits vacuole; contents move away from cell wall