Membrane Properties

Question 1

What is the difference between a channel and a carrier?

Answer 1

A channel is like a tube

A carrier is only open on one side at a time

Question 2

In the Na/K pump, what does sodium take out of the cell with it?

Answer 2

Glucose

Question 3

Electric potentials are generated across what?

Answer 3

The membranes of neurons, and all cells

Question 4

Why/how is an electric potential generated across membranes?

Answer 4

There are difference in the concentrations of specific ions across nerve cell membranes
The membranes are selectively permeable to some of these ions

Question 5

How are the resting membrane potentials, action potentials, the synaptic potentials and receptor potentials generated?

Answer 5

By the channels and active transporters working against each other

Question 6

In which cell domain are voltage gated channels found?

Answer 6

Axonal domain

Question 7

In which cell domain are ligand-gated ion channels found?

Answer 7

Somatodendritic domain

Question 8

What part of the cell is the action potential generation zone?

Answer 8

Axon hillock

Question 9

Which part of the neuron has only voltage-gated Na and K channels?

Answer 9

Axon

Question 10

Which part of the neuron has voltage-gated Na, K and Ca channels?

Answer 10

Nerve termini

Question 11

Is the concentration of Na higher in the cell, or out of the cell?

Answer 11

Outside of the cell

Question 12

Is the K concentration higher in or out of the cell?

Answer 12

In the cell

Question 13

Where is the potential difference found?

Answer 13

In the cell membrane

Question 14

What two factors influence the actual voltage of a membrane potential?

Answer 14

Ionic concentration gradient

Membrane permeability

Question 15

In almost all cases, the resting membrane potential is primarily due to what?

Answer 15

The leak of K ion out of the cell without a counter ion balancing the charge

Question 16

The rate of ion flux across a membrane is a function of what?

Answer 16

The driving force acting on the solute/ion

The permeability of that ion across the membrane

Question 17

The driving force acting on a solute/ion is a function of what?

Answer 17

Concentration gradient

Membrane potential

Question 18

Passive flux of all solutes will continue until what occurs?

Answer 18

The solute is at equilibrium across the membrane

Question 19

What is the net flux of a solute across a membrane at equilibrium?

Answer 19

0

Question 20

Ions come into “electrochemical equilibrium” where net flux of the ion may equal zero, and what may still be present?

Answer 20

A concentration gradient

Question 21

What is the electrochemical gradient?

Answer 21

A combination of the chemical gradient (concentration) and the electrical gradient (membrane potential)

Question 22

How is the membrane potential generated?

Answer 22

By differential ionic permeabilities across the membrane - generally due to selective permeability of the membrane for specific solutes

Question 23

As K moves between chambers, it adds a small amount of ___ charge on the one side, and leaves a small amount of ___ charge on the other.

Answer 23

Positive

Negative

Question 24

Which equation is used to calculate the equilibrium potential?

Answer 24

Nernst equation

Question 25

Voltage is not the same for all cells, and may very over time. Why?

Answer 25

Vm is a function of 2 parameters:

1. Concentration gradients of those ions across the membrane
2. Permeability of the various ions

Question 26

Under resting conditions, what is the most permeable ion?

Answer 26

K

Question 27

What does the Goldman-Hodgkin-Katz equation take into account?

Answer 27

All ion concentrations both inside and outside of the cell

Question 28

Is Ex a real or theoretical value?

Answer 28

Theoretical value - provides a theoretical boundary for Vm if permeability for one ion predominates

Question 29

Vm will vary based on what?

Answer 29

Cell type

Question 30

What does TEPD stand for?

Answer 30

TransEpithelial Potential Difference

Question 31

The magnitude of the TEPD is proportional to what?

Answer 31

The tightness of the tight junctions