GCSE Biology: Osmosis and diffusion

Movement of particles and water across partially permeable membranes.

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Define diffusion.
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The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
Is diffusion an active or passive process?
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Passive — it does not require energy from the cell.
Define osmosis.
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The net movement of water molecules across a partially permeable membrane, from a region of higher water concentration to a region of lower water concentration.
Osmosis is a special case of ? that applies to water.
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diffusion
What does a partially permeable membrane allow through in osmosis?
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Water molecules, but not larger solute molecules such as sugars and salts.
What happens to an animal cell placed in a very dilute solution?
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Water enters by osmosis, and the cell may swell and burst (lysis).
When an animal cell is placed in a concentrated solution, it shrinks — a process called ?.
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crenation
Why do plant cells behave differently from animal cells in osmosis?
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Because of their rigid cell wall.
What happens to a plant cell placed in a dilute solution?
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It becomes turgid and firm, which supports the plant.
In a concentrated solution, a plant cell becomes flaccid and eventually ? as the membrane pulls away from the wall.
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plasmolysed

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