BIOL 364 Lecture 5: lect 5.2 notes membranes
18 Oct 2016
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11. 4 nongated ion channels and the resting membrane potential. The plasma membrane contains channel proteins that allow the principal cellular ions (na+, k+, ca2+, and cl-) to move through them at different rates down their concentration gradients. Ion concentration gradients generated by pumps and selective movements of ions through channels constitute the principal mechanism by which a difference in voltage, or electric potential, is generated across the plasma membrane. Atp-powered ion pumps generate difference in ion concentration across the plasma membrane, ion channels utilize these concentration gradients to generate a tightly controlled electric potential across the membrane. The inside cytosolic face of the cell membrane is always negative with respect to the exoplasmic face. Selective movement of ions creates a transmembrane electric gradient. If the membrane is impermeable to all ions, no ions will flow across it. Introduce na+ channel, and na flows down its conc gradient from right to left.
