facilitated diffusion

• uses carrier and channel proteins
• some larger molecules (amino acids, glucose) ions and polar molecules don't directly diffuse through phospholipid bilayer

  so diffuse through carrier and channel proteins in the cell membrane
• moves particled down a concentration gradient high to low
• passive process
• carrier proteins move large molecules into or out the cell down their concentration gradient

  1. large molecule attaches to carrier in the membrane
  2. protein changes shape
  3. releases molecule on opposite side of the membrane
• carrier protein process :

  A) high concentration of large molecules

  B) large molecule

  C) binding site

  D) plasma membrane

  E) low concentration of large molecules

  F) carrier proteins

  
• channel proteins form pores in the membrane for charged particles to diffuse through ( down conc grad )

  different channel proteins facilitate the diffusion of different charged particles
• channel proteins

  A) high conc of charged particles

  B) charged particle

  C) plasma membrane

  D) channel protein

  E) low conc of charged particles