movement in cells

• Simple diffusion

  The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient
• Molecules that enter and leave cells via simple diffusion through the cell membrane


  Small molecules e.g. oxygen, water, glucose, amino acids
• Factors affecting the rate of diffusion

  • Temperature
  • Concentration gradient
  • Surface area of cell membrane
• Osmosis

  The net movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane
• Active transport

  The movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, against the concentration gradient, using energy
• what is the concentration gradient

  the difference in concentration of a substance between 2 areas
• how is percentage change in mass calculated 


  final mass - initial mass divided by initial mass x 100