Lecture 1

Question 1

how many TMDs does a functional voltage gated ion channel require?

Answer 1

24

Question 2

How are the transmembrane domains structured in K channels

Answer 2

Composed of 4 subunits, each with 6TMDs

Question 3

How are the transmembrane domains of Na and Ca channels structured

Answer 3

Simply as 24 transmembrane domains

Question 4

What is the role of the P loop/ pore region

Answer 4

Acts as a selctivity filter with a highly conserved amino acid sequence within them.

Question 5

What is the equation for total current carried by a population of channels (I)

Answer 5

I = N . Po . g . (Vm - Ei)
Where N = The number of channels
Po = the open probability of the channels
G = a single channels conductance
Vm = the membrane potential
Ei = the Nernst potential for ion i
(Vm - Ei) = The driving force for ion movement

Question 6

What is the Nernst potential of an ion

Answer 6

electrical potential necessary to keep an ion from diffusing out/in of the cell, down its chemical gradient.

Question 7

What is the Nernst potential for K and Na

Answer 7

K = -90 
Na = +61

Question 8

What is TEA

Answer 8

A potassium channel blocker, after application of TEA to a cell membrane potential will change if TEA sensitive cells are present. As K more readily moves out of the cell by blocking this movement the membrane potential becomes more positive, away from Ek.

Question 9

Does patch clamp measure the current through a single ion channel or all the channels on a cell

Answer 9

The current through a single ion channel.

Question 10

How is the current magnitude determined in the patch clamp method

Answer 10

Determined by the channels open at the potential and the driving force for ion movement through the channel.

Question 11

What is changed upon each repeat of the patch clamp trchnique

Answer 11

The voltage that the cell is clamped to - record changes in current as a result

Question 12

What is an IV curve

Answer 12

Y axis = Current

X axis = Voltage

Question 13

What is a positive (outward) current

Answer 13

Means there is a net movement of cations out of the cell or anions into the cell

Question 14

What is a negative (inward) current

Answer 14

Means there is a net movement of anions out of the cell or cations moving into the cell.

Question 15

What is the effect of ion channel blockers on IV curves

Answer 15

Bring the currents closer to 0

Question 16

What are Pro-Tx-II and tetrodotoxin

Answer 16

Both are Na channel blockers
Pro-Tx-II is an Nav1.7 inhibitor which reduces excitability of sensory neurons of nociception
Tetrodotoxin is a potent neurotoxin that blocks Na channels, preventing action potential generation and propagation leading to paralysis in humans

Question 17

How does two-electrode differ to patch clamp

Answer 17

One electrode clamps the potential and another measures the current