Flashcards in OSMOSIS Deck (24)
Loading flashcards...
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
