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Flashcards in OSMOSIS Deck (24)
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1

What is osmosis

the passage of water from a region where it has a higher water potential to a region where it has a lower water potential through a electively permeable membrane

2

What is a solute

any substance that is dissolved in a solvent

3

What is water potential measured in

kiloPascals (kPa)

4

When does pure water have a water potential of 0

25 degrees C, 100kPa

5

What does the addition of a solute to pure water do to the water potential

lowers it

6

What must be water potential of a solution must be

below 0 (negative)

7

What is a solution

solute and water

8

What happens to the water potential as more solute is added

it lowers (becoes more negative)

9

What is a method of finding the water potential of cells or tissues

place them in a series of solutions of different water potentials, the water potential where there is no net gain or loss of water from the cells means that that is the water potential inside the cell/tissues

10

What are 2 soutions called if they have the same water potential

isotonic

11

What form of water has the highest water potential

pure water

12

What does the rate of osmosis depend on (3 points)

1) water potential gradient
2) thickness of the exchange surface
3) surface area:volume ratio of exchange surface

13

How does the water potential gradient affect the rate of osmosis

higher water potential gradient = faster rate of osmosis up to a point (equilibrium reached)

14

How does the thickness of the exchange surface affect the rate of osmosis

thinner = faster rate of osmosis

15

How does the SA:V ratio affect the rate of osmosis

larger SA:V ratio = faster rate of osmosis

16

How do you carry out a serial dilution (4 points)

1) line up 5 test tubes
2) add 10cm3 of the initial 2M sucrose solution to the first test tube and 5cm3 of distilled water to the other
3) draw 5cm3 of the first test tube to the second
4) repeat for each of the other test tubes

17

What is an alternative to a serial dilution

find a scale factor

18

How do you find the water potential of potato cells

1) cut the potatos into identically sized chips
2) measure the mass of each potato chip
3) place one into each tube of different sucrose solutions
4) leave the chips in the solution for 20 mins
5) remove the chips and dry gently with a paper towel
6) weigh each potato chip
7) calculate the % change in mass
8) use the results of make a calibration curve showing % change in mass against sucrose solution

19

What happens if red blood cells are placed in a solution with a water potential lower than its own

water leaves by osmosis and the cell shrinks & becomes shrivelled

20

What happens if a cell is put in a solution with a water potential higher than its own

water enters cell by osmosis so it swells & bursed

21

What happens when a cell is put in a solution with a water potential equal to its own

no water enters or leaves, so there is no change

22

When does a plant cell become turgid

when water enters the cell by osmosis

23

When does a plant cell become incipient plasmolysis

when the protoplast no longer presses on the cellulose cell wall

24

When does a plant cell become plasmolysed

when the cell contents shrink and the protoplasts pull away from the cell wall