osmosis

• what type of membrane is needed for osmosis to happen?

  a partially permeable one(it has small holes in it, so only tiny molecules can pass through)
• true or false? oxygen entering the blood from the lungs is an example of osmosis.

  false. this happens by diffusion. osmosis involves the movement of water.
• when plants lose water, they start to wilt. explain why most plants will wilt if the soil they are growing in is flooded with salty sea water.


  the sea water has a concentration of salt, so the water concentration in the soil will be lower than that in the plant. this means water would move by osmosis from the plant to the soil - from a high to low concentration. this causes the plant to loose water and wilt.
• what is osmosis?

  • Process by which water molecules move from an area of high concentration to an area of low concentration
  • Occurs across a semi-permeable membrane
  • Does not require energy
  • Example: When water moves into a plant cell
• what is passive transport?

  • Type of transport that does not require energy
  • Molecules move from an area of high concentration to an area of low concentration
  • Examples: Diffusion and osmosis
• what is active transport?

  • Type of transport that requires energy
  • Molecules move against the concentration gradient
  • Uses enzymes to move molecules across the cell membrane