Osmosis

Question 1

what is the symbol of water potential?

Answer 1

ψ

Question 2

what is the definition of water potential?

Answer 2

the pressure exerted by the water molecules as they collide with a membrane

Question 3

what is water potential measured in?

Answer 3

pressure Pa or kPa

Question 4

what is the water potential of pure water?

Answer 4

0 kPa at standard temp and atmospheric pressure

Question 5

what is the highest possible water potential value?

Answer 5

0 kPa

Question 6

is the presence of a solute lower or raise the ψ?

Answer 6

it will always lower the ψ to negative values

Question 7

the more concentrated the solution…

Answer 7

…the more negative the ψ

Question 8

what is the definition of osmosis?

Answer 8

the net movement of water from a higher water potential (less concentrated) to a lower water potential (more concentrated) across a partially permeable membrane, until equilibrium is reached

Question 9

what does water potential describe?

Answer 9

the tendency of water to move out of a solution

Question 10

what water potential does a dilute solution have?

Answer 10

high water potential

Question 11

what water potential does a concentrated solution have?

Answer 11

low water potential

Question 12

what do the words turgid and plasmolyse relate to?

Answer 12

plant cells

Question 13

what do the words cytolysis and crenate relate to?

Answer 13

animal cells

Question 14

what is the definition of turgid?

Answer 14

when water diffuses into the plant cell through a partially permeable membrane via osmosis, down its water potential gradient, causing the cell to become swollen. the cell contents pushes against the cell wall, this resists any further swelling. as more water enters, eventually the water potential outside is equal to the inside, and the cell reaches it’s equilibrium

Question 15

what is the definition of plasmolysed?

Answer 15

this is when the cytoplasm shrinks in a plant cell and the membrane pulls away from the cellulose cell wall. the plasma membrane becomes damaged and the cell usually dies.

Question 16

what is a collection of cells in a tissue in a plasmolysed state described as?

Answer 16

flaccid

Question 17

what is the definition of cytolysis?

Answer 17

in animal cells, if a lot of water molecules diffuse into it via the plasma membrane (down the water potential gradient), the cell will swell and burst, resulting in the plasma membrane breaking

Question 18

what is the definition of crenate?

Answer 18

if water diffuses out of animal cells, down their water potential gradient, the cells may shrink, shrivel and become ‘star shaped’

Question 19

what is a hypotonic solution?

Answer 19

when the solution has a higher water potential than the cell (to remember, it is less concentrated)

Question 20

what is a hypertonic solution?

Answer 20

when the solution has a lower water potential than the cell (to remember, it is more concentrated)

Question 21

what is an isotonic solution?

Answer 21

the solution outside of the cell has the same solute concentration as the inside of the cell

Question 22

what happens if placed in a hypotonic solution with a higher water potential than the animal cell?

Answer 22

-water moves in, down the water potential gradient, via osmosis, increasing the hydrostatic pressure inside the cell

Question 23

if placed in a hypertonic solution with a higher water potential than the animal cell, what will the end result be?

Answer 23

because the cell membrane is thin, and there is no cell wall, it cannot withstand this pressure, it will burst (cytolysis)

Question 24

what happens if placed in a hypertonic solution that has a lower water potential than the animal cell?

Answer 24

-water moves out of the cell, down the water potential gradient, via osmosis

Question 25

if placed in a hypotonic solution with a lower water potential than the animal cell, what will the end result be?

Answer 25

the water moving out of the cell via osmosis causes animal cells to shrink (crenation)

Question 26

what happens if the water potential is equal either side of the plasma membrane? animal cell

Answer 26

there is no net movement of water via osmosis, the solution is isotonic

Question 27

example of isotonic solution in our bodies

Answer 27

our bodies have control mechanisms to ensure our blood is isotonic to our cells to maintain water potential gradients

Question 28

what is a protoplast?

Answer 28

between cell wall and membrane (not in spec but may get asked question)

Question 29

what happens if the plant cell is in a hypotonic solution (solution has a lower water potential)?

Answer 29

-water moves out of the cell via osmosis, down the water potential gradient

Question 30

what is the end result of placing a plant cell in a hypotonic solution (solution has a lower water potential)?

Answer 30

the vacuole shrinks and the plasma membrane detach from the cell wall- the cell has become plasmalysed
-protoplast completely pulled away from cell wall (not in spec but may get quetsions)

Question 31

what happens if the plant cell is in a hypertonic solution (solution has a higher water potential)?

Answer 31

-water moves into the cell via osmosis, down the water potential gradient

Question 32

what is the end result if the plant cell is in a hypertonic solution (solution has a higher water potential)?

Answer 32

-tugor pressure inside the cell increases and the vacuole and the cytoplasm swells and pushes against the cell wall
-the cell is turgid
-protoplast pushed up against the cell wall

Question 33

why does osmosis stop when plant cell is in hypertonic solution?

Answer 33

the cell wall is inelastic and will not burst, this will stop any further osmosis

Question 34

what happens to a plant cell when there is equal water potential?

Answer 34

there is no net movement of water via osmosis, the solution is isotonic

Question 35

what is the end result of a plant cell in an isotonic solution?

Answer 35

the protoplast will begin to pull away from the cell wall