2014 Ion Channel Physiology

Membrane biochemistry
(from a physiology perspective!)

A cell’s phospholipid bilayer limits the passage of charged molecules (especially ions) across the cell membrane (i.e., the lipid part of the cell membrane has high electrical resistance).  Gap junctions, membrane transporters and ion channels provide routes for charged molecules to move from one side of the cell membrane to the other.  Transporters and channels have fundamentally different properties.
Critical Fact Icon
CHANNELS
PUMPS
  • channels represent a direct connection between the intracellular and extracellular spaces
    (i.e., they are "HOLES")
  • there is never any connection between the intracellular and extracellular spaces
  • move small molecules (ions, water)
  • can move larger molecules (e.g., glucose)
  • ALWAYS move charged molecules DOWN their concentration gradients (from high concentrations to low) i.e., passive

--> dissipate concentration gradients

  • by using ATP, some pumps (antiports) can move molecules AGAINST their concentration gradients (from low concentrations to high) i.e., active

--> build up concentration gradients

  • extremely high speed
    (10x106 molecules/s)
  • slower (1x103 molecules/s)

 

Email: Dr. Janet Fitzakerley | ©2014 University of Minnesota Medical School Duluth | Last modified: 20-sep-14 10:16 AM