Chapter 2: Diffusion and Osmosis

• What is diffusion?

  Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
• What is osmosis?

  Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration across a semi-permeable membrane.
• What is active transport?


  Active transport is the movement of molecules or ions across a cell membrane against their concentration gradient, requiring energy.
• in plant cell, when a cell is placed in a solution with higher water potential it:

  • vacuole size increases
  • presses the protoplasm against the cell wall
  • plant swells up and turns turgid but does not burst
• in plant cell, when a cell is in a solution with a lower water potential it

  • vacuole decreases in size and turns flaccid
  • cytoplasm shrinks away from the cell
  • cell is plasmolysed
• what does crenate mean?

  having a margin with toothed edges
• what does plasmolysed mean?

  shrivel up and shrink and become flaccid