AQA · Biology · 8461
GCSE Biology: Osmosis
Cell biology · AQA GCSE Biology (8461), specification point 4.1.3.2. Cards are generated from the exam board's own specification for "Osmosis", and every card links back to the page it came from. Specification © AQA — used with attribution.
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Define osmosis.
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The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
In osmosis, water moves through a ? membrane.
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partially permeable
In osmosis, does water move towards the dilute or the concentrated solution?
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Towards the concentrated solution (from the dilute solution, down the water concentration gradient).
By which process does water move across cell membranes?
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Osmosis.
What is a partially permeable membrane?
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A membrane that lets some molecules (e.g. water) pass through but not others (e.g. larger solute molecules).
How is the percentage change in mass of plant tissue calculated?
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(Final mass − initial mass) ÷ initial mass × 100. A positive value is a gain, a negative value a loss.
What does GCSE Biology required practical 3 (osmosis) investigate?
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The effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue.
Why does plant tissue gain mass in a dilute solution?
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Water moves into the cells by osmosis, because the solution outside is more dilute than the cell contents.
Why does plant tissue lose mass in a concentrated salt or sugar solution?
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Water moves out of the cells by osmosis, because the solution outside is more concentrated than the cell contents.
Why use percentage change in mass rather than absolute change in the osmosis practical?
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Pieces of plant tissue have different starting masses, so percentages allow fair comparison between samples.
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