BRAINCAKETurgor Pressure (P)
Turgor pressure (P) is the pressure exerted by the protoplast (the cell contents) pushing outwards against the cell wall. The wall pushes back on the contents with an equal and opposite pressure, sometimes called wall pressure. Turgor pressure is also called pressure potential, written ψp.
How it builds up: when water enters a plant cell by osmosis, the vacuole and cytoplasm swell. The cellulose wall is strong and only slightly elastic, so it resists further expansion. The contents become pressurised, just as air pressure builds up in a tyre being pumped up.
Key facts about turgor pressure:
• In a living plant cell it normally has a positive value, for example +400 kPa.
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Key terms in this lesson
- water potential
- A measure of the tendency of water molecules to move out of a solution; water moves from a higher to a lower (more negative) water potential.
More in Cell Transport Mechanisms
- Osmotic Concentrations
- Osmosis in Animal Cells
- Water Potential in Plant Cells
- Osmosis in Plant Cells
- Osmotic Potential (π)
- Water Potential, Turgor Pressure and Osmotic Potential
- Active Transport
- Evidence for Active Transport
All 18 lessons in Cell Transport Mechanisms · All Edexcel AS-level Biology topics