Exchanging Substances

• What is diffusion?

  Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
• Name three substances that can diffuse through cell membrane, and two that can’t.

  1. oxygen✅
  2. amino acids✅
  3. glucose✅
  4. starch❌
  5. proteins❌
• What type of molecules move by osmosis?

  Water molecules.
• Give the two main differences between active transport and diffusion:

  Active transport requires energy from the cell

  Active transport requires a specific channel to pass through.

  • Diffusion requires no energy from the cell
  • Diffusion requires no specific channel to pass through
• Give three adaptations of exchange surfaces that increase the efficiency of diffusion:

  Large surface area, thin membrane, high concentration gradient
• Give two ways that the villi in the small intestine are adapted for absorbing digested food?

  villi are inside the small intestine and used for absorption of nutrients and shuttle then into your bloodstream to travel where they need to be.

  • Increased surface area
  • a very good blood supply to assist quick absorption
• Explain how leaves are adaption to maximise the amount of carbon dioxide that gets to thier cells?

  Stomata

  • the structure of the leaves are adapted to let gases diffuse in and out of the cells

  flattened shape of the leave increases the area of this exchanged surface so that it’s more effective