diffusion and osmosis

• Active transport

  The movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration, requiring energy from cellular respiration
• Active transport

  • Takes place across a membrane
  • Requires special proteins in the membrane to transfer molecules
• Cellular respiration

  Provides the energy for active transport
• Root hair cells

  • Have a large surface area for absorption
  • Have many mitochondria to provide energy for active transport
• Osmosis

  The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• Osmosis in cells

  Water particles diffuse from the outside of the cell (higher water concentration) down the concentration gradient into the cell (lower water concentration)
• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
• Osmosis is a special case of diffusion, specifically the diffusion of water molecules
• Diffusion

  The net movement of particles from an area of higher concentration to an area of lower concentration
• Diffusion can happen in both gases and liquids
• Partially permeable membrane

  Only some molecules can diffuse through, like water, glucose, and amino acids. Larger molecules like proteins and starch cannot fit through.
• Diffusion is a passive process that does not require energy from the cell
• Factors affecting rate of diffusion

  • Concentration gradient - larger concentration gradient means higher rate of diffusion
  • Temperature -higher temperature give particles more energy and increases the rate of diffusion
  • Surface area - large surface area means faster rate of diffusion
• how would you investigate osmosis in potatoes?

  1. prepare a range of sucrose solutions
  2. set up a series of boiling tubes with each solution
  3. cut the potatoes into strips and weight them, dry beforehand
  4. place in 0% solution for 20 mins then try with diff concentrations
  5. then repeat with diff potato strips