Diffusion

• How does the concentration gradient affect the rate of diffusion?

  A steeper concentration gradient increases the rate
• How does membrane thickness affect the rate of diffusion?

  Thinner membranes increase the rate of diffusion
• How does surface area affect the rate of diffusion?

  Larger surface areas increase the rate of diffusion
• How does temperature affect the rate of diffusion?

  Higher temperatures increase the rate of diffusion
• How is facilitated diffusion different from simple diffusion?

  It uses proteins to facilitate the process
• How do the number of channel or carrier proteins affect the rate of facilitated diffusion?

  More proteins increase the rate until they are all in use
• Define simple diffusion.

  The net movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached. This process does not require ATP, and therefore it is a passive process.
• Define facilitated diffusion.

  Carrier and channel proteins are used to transport molecules across the cell membrane.
• How do channel proteins move molecules across the cell membrane?

  They form tubes filled with water and this enables water-soluble ions to pass through the membrane.
• How do carrier proteins move molecules across the cell membrane?

  Carrier proteins will bind with a molecule, such as glucose, which causes a change in the shape of the protein. This change in shape enables the molecule to be released to the other side of the membrane.