2.1 Osmosis and Plant Transport
Osmosis, plasmolysis and turgidity, plant-tissue investigation, water uptake, transpiration and potometer evidence.
How to study for CCEA GCSE Biology
Learn each process as a structure-and-mechanism chain, use data with units, and prepare every prescribed practical from planning through conclusion and evaluation.
Core concepts
Concept 1
Osmosis is water movement from a dilute to a more concentrated solution through a selectively permeable membrane.
Exam cue: State the relative solution concentrations, membrane and direction of net water movement.
Concept 2
Plant cell walls resist expansion as water enters, producing turgidity; water loss can make the membrane pull from the wall in plasmolysis.
Exam cue: Calculate percentage change from the initial measurement and retain the sign when interpreting mass or length data.
Concept 3
A potometer estimates water uptake rather than directly measuring transpiration, and light, temperature, wind, humidity and leaf area affect the rate.
Exam cue: Distinguish what the apparatus measures from the biological process inferred from that measurement.
Risk pitfalls and guardrails
Describing osmosis as movement of solute or as any movement through a membrane.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Calling a plasmolysed plant cell burst when its cell wall limits expansion.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Claiming every change in bubble movement is caused only by transpiration.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a biological mechanism with a vague purpose statement.
Memory anchors
Osmosis
Net water movement from dilute to concentrated solution through a selectively permeable membrane.
Turgid cell
A plant cell firm from water entry and pressure against the cell wall.
Plasmolysed cell
A plant cell whose membrane has pulled from the wall after water loss.
Transpiration
Water evaporation from mesophyll followed by diffusion through air spaces and stomata.
Potometer
An apparatus that estimates plant water uptake as a proxy for water loss.
Percentage change
Final minus initial, divided by initial, multiplied by 100.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Which description correctly explains water movement by osmosis across a selectively permeable membrane?
A plant cell is placed in dilute solution. Why does it become turgid?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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