Facilitated diffusion occurs
   when material diffuse across the plasma membrane via proteins embedded
   in the membrane.
<P>
<lI> Channel  proteins provide corridors that allow a specific particle
to cross the membrane.
<lI> Carrier  proteins  undergo a change in shape that translocates the
solute-binding site across the membrane.
<P>
   These  are  passive  transport mechanisms that move solutes down their
   concentration gradient.
<P>
   Review:  <A ClAsS=ACT Href="http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/activities/load.html?7&amp;E" oNClick="popact('http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/activities/load.html?7&amp;E');txtcolor('facilitated_diffusion1','gray');return false;" Id=facilitated_diffusion1><iMg sRc="/images/tutorial.gif" aLt='' boRDer=0></A>