4.3- Osmosis

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  • Created by: Megan2413
  • Created on: 14-12-16 17:33
What is osmosis?
The net movement of water particles from an area of high water potential to low water potential through a partially permeable membrane
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What is water potential?
The potential (likelihood) of water molecules to diffuse in or out of a solution
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Pure water has the highest or lowest water potential?
Highest water potential
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If two solutions have the same water potantial- what are they said to be?
Isotonic
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What three factors affect the rate of osmosis?
- Water potential gradient - Thickness of exchange surface - Surface area of the exchange surface
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What is a serial dilution?
A technique by which a stock solution is diluted by a known amount each time, producing a series of dilutions
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How would you make a serial dilution starting with a 2M sucrose solution and diluting each solution by a factor of 2?
- Line up 5 test tubes in a rack - Add 10cm3 of the initial 2M sucrose solution to the first test tube - add 5cm3 of distilled water to the other 4 test tubes - Use a pipette to add 5cm3 of the 2M sucrose solution from the first test tube and add it
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-->
to the second test tube, and mix the solution - Repeat the process from the second test tube to the third, and so on - Each test tube will be half as concentrated as the last one
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How would you make 15cm3 of a 0.4M solution?
- Solution of known concentratioin: 1M - S.f. = 1M/0.4M = 2.5 - 15cm3/2.5 = 6cm3 - Add this amount of the solution to a test tube with (15-6=9) 9cm3 of distilled water to make up 15cm3 of a 0.4M solution
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What equipment would you use to cut a potato during an osmosis experiment?
Cork borer
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What measurement would you take before and after the potato chip osmosis experiment?
The mass of the potato chips
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Why do you need to blot the potatos before and after weighing them?
To measure only the mass lost or gained by osmosis, surface water mass should be discluded from the results
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Where is the point at which the water potentials in this experiment are isotonic on a graph?
Where the calibration curve meets the X-axis
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What is a calibration curve?
A general method to determine the concentration of a solution of an unknown sample against a set of standard samples of known concentration
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What is water potential measured in?
KPa (KiloPascals)
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What is the water potential of pure water under standard conditions (25 degrees celcius and 100KPa)?
0KPa
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Should the KPa of other water solutions be more or less than 0
Less than 0KPa
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Water will move from a negative water _________ to a ___ negative water potential
- Potential - more
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What does hypotonic mean?
A solution with a higher water potential than to one which it is being compared
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What does isotonic mean?
A solution which has the same water potential to one hich it is being compared
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What does hypertonic mean?
A solution with a lower water potential to one which it is being compared
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What happens when a plant cell is turgid?
Water enters the cell and it swells a bit, pushing the protoplast against the cell wall
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What happens when a plant cell undergoes incipient plasmolysis?
The protoplast is beginning to pull agaisnt the cell wall but overall there is no net movement of water
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What happens when a cell is plasmolysed?
Water leaves the cell and the protoplast completely pulls away from the cell wall, shrinkig the cytoplasm
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What is lysis?
The bursting of animal cells due to osmosis
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What is haemolysis?
The bursting of a red blood cell due to osmosis
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The lower the water potential, the ______ negative it becomes
more
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Other cards in this set

Card 2

Front

What is water potential?

Back

The potential (likelihood) of water molecules to diffuse in or out of a solution

Card 3

Front

Pure water has the highest or lowest water potential?

Back

Preview of the front of card 3

Card 4

Front

If two solutions have the same water potantial- what are they said to be?

Back

Preview of the front of card 4

Card 5

Front

What three factors affect the rate of osmosis?

Back

Preview of the front of card 5
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