Passive transport is a naturally occurring phenomenon and
does not require the cell to exert any of its energy to accomplish the movement. Diffusion also falls under passive transport where ions from high concentration to
low, using no metabolic energy. In facilitated transport materials diffuse across the plasma
membrane with the help of membrane proteins. In facilitated
transport the material being transported is first attached to protein or glycoprotein
receptors on the exterior surface of the plasma membrane. This allows the material that is
needed by the cell to be removed from the extracellular fluid.