Osmosis

  • Created by: annaquinn
  • Created on: 13-06-18 19:20
What is osmosis?
Osmosis is where water diffuses through a dilute solution to a more concentrated solution through a selectively permeable membrane.
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What happens when a cell is placed in a dilute solution?
It becomes lysed
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Describe this.
1. Water moves by osmosis 2. dilute->concentrated 3. Through permeable membrane 4. Cell swells and bursts.
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What happens when a cell is placed in a concentrated solution?
It becomes shrivelled.
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Describe this.
1. Water moves out by osmosis 2. dilute->concentrated 3. Through permeable membrane 4. Cell shrivels up.
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How does a cell become turgid?
When placed in pure water
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Describe a turgid cell.
Water enters cell, cell is more concentrated than surroundings, vacoule expands which causes turgor pressure, cell wall limits water intake.
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How does a cell become plasmolysed?
When placed in concentrated solution
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Describe a plasmolysed cell.
Cell loses water by osmosis, cell loses turgor causing the vacoule to shrink, membrane peels away from cell wall.
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What 4 ways do plants use water?
1. Support- turgor pressure 2. Transpiration- movement of water up a plant 3. Transport 4. Photosynthesis
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What does a bubble potometer do?
Measure water uptake as the bubble moves along the scale.
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How is it set up?
In water (to ensure it's airtight) and in different conditions
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How do we calculate the rate?
Distance divided by the time / mass loss divided by the time
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What does a weight potometer do?
Measure loss in mass over 24 hours
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How is it set up?
In different conditions and covered up soil to avoid any water loss.
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What is transpiration?
Water moving from roots to leaves, evaporation off leaf cell surfaces and the diffusion of water vapour out of stomata.
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What effect does windspeed have have on transpiration?
Evaporation is HIGHER in faster windspeed, wind rapidly moves diffusing water away from stomata, steep concentration GRADIENT at leaf surface and this means water is EASILY LOST and so rate of transpiration INCREASES.
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What is humidity?
The water content in the air
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What effect does this have on transpiration?
More humid=more water=less transpiration, concentration gradiant DECLINES between leaf and air and there is less water loss.
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What effect does surface area (number of leaves) have on transpiration?
More surface area=more stomata=more water loss by evaporation and diffusion
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Two important points ->
When using potometer, use same shoot to ensure surface are is constant and the stomata can close to reduce water loss.
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What effect does temperature have on transpiration?
Warmer conditions ensure water evaporates faster, high temp=faster movement of molecules, steep concentration gradient, rate of transpiration INCREASES.
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Give the 2 steps of the potato mass experiment.
1. Cylinders of weighed potatos are placed in different concentrations of solutions 2. They are dried and reweighed, calculate the loss/gain in mass
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What happens to the potato when placed in a concentrated solution?
LOSS in mass= water leaves cells by osmosis
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What happens to the potatoe when placed in a dilute solution?
GAIN in mass= water enters cells by cell osmosis
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3 important points ->
1. Could also use carrot! 2. Controlled variables (what are they?) 3. Loss of mass NOT length
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Describe the onion cells plasmolysis practical.
Onion epidermis is placed in different concentrated solutions, viewed under a microscope, cells plasmolyse in concentrated solutions, cells become turgid in dilute solutions
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Important point ->
SAME SOLUTION is used to prepare slide
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Other cards in this set

Card 2

Front

What happens when a cell is placed in a dilute solution?

Back

It becomes lysed

Card 3

Front

Describe this.

Back

Preview of the front of card 3

Card 4

Front

What happens when a cell is placed in a concentrated solution?

Back

Preview of the front of card 4

Card 5

Front

Describe this.

Back

Preview of the front of card 5
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