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All 13 Flashcards — Osmosis in cells with a wall
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Question
Define osmosis.
Answer
The **net movement of water** across a partially permeable membrane, from a **higher water potential (dilute)** to a **lower water potential (concentrated)**.
Question
What is the cell wall's role in osmosis?
Answer
It is **fully permeable** (water passes through), but it **resists pressure** so the cell does not burst — making the cell turgid instead.
Question
Define turgor pressure.
Answer
The **outward pressure** of the cell contents pushing against the cell wall when a plant cell has taken in water.
Question
What does 'turgid' mean?
Answer
A plant cell that is **full of water and firm**, with the contents pressing hard against the wall (high turgor pressure).
Question
What does 'flaccid' mean?
Answer
A plant cell that has **lost water and is limp**, with little or no turgor pressure pushing on the wall.
Question
Define plasmolysis.
Answer
When a plant cell loses so much water that the **cytoplasm and membrane pull away from the cell wall**.
Question
What happens to a plant cell in a HYPOTONIC solution?
Answer
Water **enters** by osmosis → the cell swells but the wall stops it bursting → it becomes **turgid**.
Question
What happens to a plant cell in an ISOTONIC solution?
Answer
**No net water movement** → low turgor → the cell is **flaccid** (limp).
Question
What happens to a plant cell in a HYPERTONIC solution?
Answer
Water **leaves** by osmosis → the cell loses turgor and becomes **plasmolysed** → the tissue wilts.
Question
In a plasmolysed cell, what fills the gap between the contents and the wall?
Answer
The **external (bathing) solution** — the fully permeable wall lets it flow in.
Question
Why does a plant cell NOT burst in pure water, but an animal cell does?
Answer
The plant cell's **strong wall resists the pressure** (it becomes turgid). The animal cell has **no wall**, so it keeps swelling and bursts.
Question
In a data experiment, what does a solution that causes NO net mass change tell you?
Answer
It is **isotonic** — the same concentration as the cell contents, so it estimates the cells' own **internal concentration**.
Question
Which way does water move relative to solute concentration?
Answer
Towards the **more concentrated** solution (lower water potential). To plasmolyse a cell the outside must be the more concentrated one.
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