Overview of Membrane Channels, Transporters, and Pumps

By Avalon Marker and Shelby Pickett

Overview of Channels

• Membrane Permeability

• The ease with which molecules pass through the membrane barrier.

• The cell membrane is selectively permeable and only allows specific molecules to enter the cell.

• The permeability of the membrane is the rate of passive diffusion of molecules across the membrane.

• (Insert image of the permeability of the different molecules)

• Resting Neuronal membrane

• Ion channels:

• • • Ion channels are integral membrane proteins composed of several subunits. The primary function of ion channels in neurons is to generate transient electoral signals.

• Categories of Channels:

• • • Leakage (include a link to the chapter on resting membrane potential)
      • Leakage gated channels always remain open for substances and ions. They have constant permeability.

• Gated Channels: open in response to specific changes in membrane potential of the channel.

• Mechanically Gated

• Voltage Gated: these channels open and close in response to specific changes in membrane potential.

• Ligand gated:

• • • • • A ligand is…
        • When the ligand binds it opens the channel.

• Signal Gated

• Transporters: a membrane protein involved in the movement of ions, small molecules, and macromolecules (such as proteins) across a membrane.

• • • • They may help with transport through facilitated diffusion, active transport, osmosis, or reverse diffusion.

• Pumps