Week 3b: Ion channel function

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Presentation transcript:

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

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

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)

The Na+/K+ ATPase

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

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.

V = I * R I = V * G

Iion = (Vm – Eion) x Gion

What is G?

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.

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

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

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

The opening and closing of single ion channels Sodium Channels

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

Single-channel currents Whole-cell currents

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