1. Week 3b: Ion channel function
BIOL3833
Week 3b: Ion channel function

2. First In-Class Quiz: Tuesday Sept 10
Delivered via Canvas
Bring computer or tablet
20 questions; 15 minutes
Opens at 12:05 ends at 12:20

3. Quick review
Equilibrium potentials (V) arise because the neuron maintains different concentrations of ions inside vs. outside the cell.
The balance point between gas diffusion force and electrostatic force is the equilibrium potential (this is a Voltage)

4. The Na+/K+ ATPase

5. rotates and interacts with the N and P domains P Domain:
Extracellular
Plasma
membrane
Intracellular
A Domain:
actuator domain
rotates and interacts with the N and P domains
P Domain:
phosphorylation domain
homologous to haloacid dehalogenase (HAD) enzymes
Contains active site for binding of magnesium ion and phosphate
N Domain:
Domain within the P domain
Includes the ATP-binding site

6. What maintains the different concentrations of ions
What maintains the different concentrations of ions? The sodium-potassium pump.
Extrudes 3 Na+ and brings 2 K+ into the cell.
The result? High concentrations of Na+ outside the cell and high concentrations of K+ inside the cell.

7. V = I * R
I = V * G

8. Iion = (Vm – Eion) x Gion

9. What is G?

10. Ion channels! Today – Analysis of ion channel function
Tuesday – Simulations
Thursday – Structure of ion channels (simulations)
Point out that different ion channels are the targets of many drugs.

11. Ion channel function What do we care about?
When does it allow ions to cross the membrane
I.e., when is it in a conducting versus a nonconducting state

14. We care about: Activation, Deactivation, Inactivation, Recovery
For each of these processes
Voltage dependence
Kinetics

15. How do we study ion channel function?
Voltage Clamp
Explain Voltage Clamp on Board

17. The opening and closing of single ion channels
Sodium Channels

18. The opening and closing of single ion channels
Sodium Channels
Potassium Channels

19. Single-channel currents
Whole-cell currents

21. Interpreting voltage clamp “families” We can find the voltage dependence & kinetics from these data
Use MatLab Program TeachTEVC