Cell Transport

• What is simple diffusion?

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


  Small molecules e.g. oxygen, water, glucose, amino acids
• What factors affect the rate of diffusion? (3)

  • Temperature
  • Concentration gradient
  • SA of cell membrane
• Define 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
• What is 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.
• How is a percentage change in mass calculated?

  percentage change = (change in mass/ initial mass) x 100