Across a normal cellular membrane, the potential is maintained with a positive charge on the outside of the cell and a negative charge on the inside of the cell. Which of the following best explains the operation of the voltage sensor in the voltage-gated sodium channel?
A) Under resting cellular conditions, the voltage sensor is normally pulled to the inside of the cell due to its high arginine content
B) Under resting cellular conditions, the voltage sensor is normally pulled to the outside of the cell due to its high lysine content
C) When the membrane is depolarized, the voltage sensor moves towards the outside of the membrane, allowing opening of the activation gate
D) Both a and c occur
E) None of the above

Question

Quizplus · Accepted Answer

The voltage sensor in voltage-gated sodium channels is sensitive to changes in membrane potential. Under resting conditions, it is positioned towards the inside of the cell due to the positively charged arginines, which are repelled by the positive exterior and attracted to the negative interior. Upon depolarization, the membrane potential becomes less negative, causing the voltage sensor to move towards the outside of the membrane. This movement triggers the opening of the activation gate, allowing sodium ions to flow into the cell.

Across a Normal Cellular Membrane, the Potential Is Maintained with a Positive