b3, chapter 1.1: Osmosis

A series of useful questions and answers to prepare for the b3 exam. Some are relatively basic, but also important. All information taken from the AQA textbook.

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  • Created by: Alisa
  • Created on: 11-04-13 15:22
What is a partially permeable membrane? Give an example.
A partially permeable membrane is a membrane which will only let some types of particles through. For example, they let water through, but not larger particles like glucose. A cell membrane is partially permeable.
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What does a dilute solution of sugar contain?
A dilute solution of sugar contains a high concentration of water (the solvent) and a low concentration of sugar (which is the solute). It's pretty self explanatory.
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What does a concentrated solution of sugar contain?
A concentrated solution of sugar contains a relatively low concentration of water (the solvent) and a high concentration of sugar (which is the solute). It really is quite easy to understand so don't feel too proud if you got it right.
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What does cytoplasm contain?
Cytoplasm contains a fairly concentrated solution of salts and sugars. Basically a gloopy substance that enjoys hoarding ions.
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What is osmosis?
A very picky and mean type of diffusion which discriminates against all kinds of particles and likes only water. In scientific terms, it is the movement of water molecules through a partially permeable membrane down a concentration gradient.
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This is a reminder question from b2: What is diffusion?
Like osmosis, but nicer and more accepting. It is the movement of any particles from an area of high concentration to an area of low concentration.
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What happens when conditions change outside of a cell?
Water moves in or out of the cell by osmosis. If the concentration of water is higher outside, then water moves into the cell. If it is low outside, water moves out. Water particles are very mainstream: they just go with the flow.
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How does osmosis restore the balance in an animal cell if water is used up in chemical reactions?
Well, it's all very clever. The more water is used up, the less there is left (I know, it's difficult). The concentration of water is therefore low, and more water moves down the concentration gradient into the cell, restoring the balance.
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How does osmosis restore balance in an animal cell if there is too much water inside the cell.
Avoid saying things like 'it spills out', because quite frankly it does not. There is a high concentration of water within the cell, so it moves out by osmosis to outside the cell where the concentration is lower, thus restoring balance.
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What problems can osmosis cause in animal cells if the solution outside is very dilute?
If the solution outside the cell is too dilute, too much water may move into the cell by osmosis, causing it to burst. Not good. Avoid using words like 'blow up', though. Seriously, stick with burst.
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What problems can osmosis cause in animal cells if the solution outside is very concentrated?
If the outside solution is very concentrated, water will continuously move out of the cell by osmosis. The cytoplasm will become incredibly concentrated and the cell will shrink and shrivel up. Again, not good.
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Why do plants need osmosis?
Plants quite like standing up straight instead of trailing across the ground looking dead like boiled spinach. At least they would if they had a brain. Osmosis is needed to support their stems and leaves.
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How do plants use osmosis to support them?
Water moves into the plant cell, causing the vacuole to swell up and press against the cell wall. Pressure builds up until no more water can enter the cell. The cell is now hard and rigid. Rigid stems = no boiled spinach look = happy plant.
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How concentrated does the solution surrounding plant cells always need to be?
It needs to be more dilute than the cytoplasm, so that water always flows in the right direction. Otherwise, the plant will have a problem on it's leaves: a problem which it will drop, because it's leaves won' t be very rigid.
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Other cards in this set

Card 2

Front

What does a dilute solution of sugar contain?

Back

A dilute solution of sugar contains a high concentration of water (the solvent) and a low concentration of sugar (which is the solute). It's pretty self explanatory.

Card 3

Front

What does a concentrated solution of sugar contain?

Back

Preview of the front of card 3

Card 4

Front

What does cytoplasm contain?

Back

Preview of the front of card 4

Card 5

Front

What is osmosis?

Back

Preview of the front of card 5
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Comments

Millie

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These are really good and entertaining but try not saying water 'concentration' because scientifically it doesn't really make sense :/ say water potential instead :)

Alisa

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Thanks Millie! I thought it was strange as well, but it said that in my textbook so I stuck to that instead. I get what you mean though. I only started these today, so I've just done the section on osmosis, but you can come back for the next one, I aim to put it on tomorrow!

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