diffusion and osmosis

• What is the nature of the cell membrane?

  It is selectively permeable.
• What are the three processes for movement through the cell membrane?

  Diffusion, osmosis, and active transport.
• What is diffusion?

  Spreading of particles from high to low concentration.
• Is diffusion a passive or active process?

  It is a passive process.
• How does temperature affect diffusion?

  Higher temperature speeds up diffusion.
• What happens to the speed of diffusion with a larger concentration gradient?

  The speed of diffusion increases.
• What is osmosis?

  Diffusion of water through a selectively permeable membrane.
• In which direction does water move during osmosis?

  From high water concentration to low water concentration.
• What happens to an animal cell in a dilute solution?

  Water enters and the cell may burst.
• Why do plant cells not burst in dilute solutions?

  The cell wall prevents bursting.
• What happens to cells in very concentrated solutions?

  They lose water and may shrivel.
• What is plasmolysis?

  When cytoplasm shrinks and pulls away from the cell wall.
• What are the key characteristics of osmosis?

  • Passive process
  • Occurs in living or non-living systems
  • Involves a semi-permeable membrane
  • Involves water only
  • Net movement from high to low water potential
• What is active transport?

  Movement of substances against a concentration gradient.
• What energy requirement does active transport have?

  It requires energy to 'pump' particles.