Channel proteins

• Form water filled pores in the membrane so hydrophilic substances can pass through
• Channels are selective to certain substances , each one has a specific 3D shape with a particular arrangement of electrical charges

  inside they channel and will only accept one type of molecule
• Some channels open and close like gates and they open with a signal
• Signals may be a change in voltage across the membrane or the binding of another molecule with the protein
• Aquaporins allow facilitated diffusion of water