Osmosis in Plant and Animal Cells
Water crosses a partially permeable membrane from the more dilute solution towards the more concentrated one. Explains turgid, flaccid and plasmolysed plant cells, and why an animal cell in pure water can burst.
What a learner can do afterwards
- Predicts which way water moves given the two solution concentrations.
- Explains why a plant cell holds its shape in pure water while a red blood cell does not.
- Calculates percentage change in mass for potato pieces left in sugar solutions of different strength.
1 · Read
Water crosses a partially permeable membrane from the more dilute side to the more concentrated side. Dilute means lots of water with little dissolved stuff. Net water movement can stop when pressure balances the osmotic pull. Molecules still move in both directions, and concentrations do not have to match.
A red blood cell in pure water swells and can burst, because water rushes in and the cell has no wall to hold it. A plant cell in pure water swells too, but its stiff wall holds firm and the cell turns turgid. That firmness is what holds a watered plant upright.
When water leaves, the pattern reverses. In strong sugar solution, a plant cell goes flaccid, then plasmolysed as its membrane pulls from the wall. Weigh potato pieces before and after: percentage change equals change divided by start, times 100.
When soil dries out, roots may not take up enough water to replace water lost from leaves. Cells lose turgor pressure, so the plant wilts. Across a partially permeable root membrane, a more concentrated soil solution can reduce water uptake compared with a dilute one.
Water moves toward the more concentrated side, cell walls help plants stay firm, and dry soil can leave roots unable to replace water lost from leaves.
The rewritten readings were written for this dataset; four academy videos imported from hoofer-content corpus. Academy videos have null license in corpus metadata.
2 · Watch
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Where it sits
Where this leads
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8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.