ASBiologyCIERevision Notes4. Cell Membranes & Transport4.2 Movement into & out of CellsComparing Osmosis in Plants & Animals

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First exams 2025

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Comparing Osmosis in Plants & Animals (CIE AS Biology)

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Osmosis in Cells: Comparison

Comparing & Contrasting the Movement of Water by Osmosis in Plant & Animal Cells Table

  Plant cells Animal cells
Cell membrane
  • Present
  • Composed of a phospholipid bilayer
  • Selectively permeable
Cell wall
  • Present
  • Composed of cellulose
  • Fully permeable
  • Absent
Osmosis of water into and out of cell
  • Can occur
Cell placed in solution with a lower water potential
  • Water leaves through the selectively permeable cell surface membrane by osmosis
  • Volume of the cell decreases
  • Protoplast shrinks / pulls away from the cell wall
  • Cell is plasmolysed
  • Water leaves the cell through the selectively permeable cell surface membrane by osmosis
  • Volume of cell decreases
  • Cell shrinks / shrivels up
Cell placed in solution with a higher water potential
  • Water enters the cell through the selectively permeable cell surface membrane by osmosis
  • Volume of cell increases
  • Protoplast expands / pushes against the cell wall
  • The cell wall withstands the increased pressure created
  • The pressure increases until the cell is rigid and firm (turgid)
  • The cell is fully inflated with water and no more can enter
  • Water enters the cell through the selectively permeable cell surface membrane by osmosis
  • Volume of cell increases
  • There is no cell wall to resist the increased pressure that is created
  • The cell membrane is eventually overstretched and the cell bursts

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    Phil

    Author: Phil

    Expertise: Biology

    Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.