Osmosis

• What happens if you place a plant cell in a beaker of pure water ?

  • There will be a lower water concentration within the plant cell than in the pure water surrounding it
  • Water will move from the beaker into the plant cell by osmosis
  • Causing cell to expand, and become turgid
• Is osmosis an active or passive process ?

  Passive - Doesn’t require any energy from the cell
• Definition of osmosis

  Net movement of water particles from an area of higher water concentration to an area of lower water concentration across a partially permeable membrane .
• Osmosis refers to the movement of which molecules ?

  Water molecules
• If sugars and salts are added to a beaker of water what will happen to the water concentration ( or water potential) ?

  Water potential will decrease
• When animal cells are placed in pure water they burst, whereas plant cells become turgid . Why is this ?

  Plant cells have a strong cell wall made of cellulose which prevents them from bursting .
• Cell membranes are said to be ’partially permeable ‘. What does this mean ?

  Only some types of molecules can pass through the membrane - other types of molecules can’t pass through
• What happens if you place a plant cell in a very salty solution ?

  • There will be a higher water concentration within the plant cell than in the salty solution surrounding it
  • Water will move from the inside of the plant cell to the outside by osmosis
  • This will cause the cell to shrink and become plasmolysed