Osmosis (Cambridge O Level Biology)

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Cara Head

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Cara Head

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Osmosis

  • All cells are surrounded by a cell membrane which is partially permeable
  • Water can move across this membrane and in and out of cells by osmosis
  • Osmosis is the net movement of water molecules from a high water potential (dilute solution) to a low water potential (more concentrated solution) across a partially permeable membrane
  • In doing this, water is moving down its concentration gradient
  • The cell membrane is partially permeable which means it allows small molecules (like water) through but not larger molecules (like solute molecules)

Partially permeable membrane diagram

osmosis-and-the-partially-permeable-membrane

Osmosis and the partially permeable membrane, where water molecules move through a partially permeable membrane from a region of high water potential to a region of low water potential

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Cara Head

Author: Cara Head

Expertise: Biology

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding