Gated Ion Channels

Question 1

18.Describe how ion transporters/pumps establish ion gradients, and therefore electrochemical gradients and voltage potentials across a membrane.

Answer 1

● Typically an ion channel is an aqueous pore
● Transport will flow down the gradient unless energy is spent
○ Coupled transporters
○ Atp driven pumps
● Ion gradients are maintained by ion pumps that require ATP
○ P-type pumps become phosphorylated by ATP which drives conformational change
○ Na/K symporter
● Some are highly selective others can allow transport of various ions

Question 2

19.Draw a diagram of an action potential illustrating the rise and fall of a membrane potential over time. Describe how three activity states of a voltage-gated ion channel propagates an action potential.

Answer 2

● A stimulus leads to depolarization (less negative) which causes a channel to open which allows a flow of sodium. When it is inactive, the initial gradient is reestablished. The channels are then closed again
● Three States ○ Closed
■ Responsive to voltage changes ○ Open
■ Allows for the transport of ions ○ Inactivated
■ Closed and not responsive to changes in voltage; reestablishing of gradient