5) Indicate whether each of the following is true or false and explain your choi

Question

5) Indicate whether each of the following is true or false and explain your choice

i) Doubling a cell’s size increases its membrane resistance because the area of the cell membrane is increased.

ii) The main cause of the resting membrane potential across cell membranes is the electrogenic Na+ - K+ pump.

iii) The voltage sensor of the voltage-gated Na+ channel is localized to all 6 transmembrane regions of domain 4.

iv) When the permeability of the cell membrane to an ion is increased, the ion’s movement is controlled solely by its concentration gradient.

Explanation / Answer

i. The answer is True.

Myelin as effectively increasing the thickness of the cell membrane, you would expect this to decrease its capacitance (thicker insulating layer). Although this is a gross over simplification of what is really happening, it turns out that myelination does have the effect of reducing membrane capacitance. However, myelination also increases the membrane resistance.

ii. The answer is True. The negative resting potential is due to the voltage-gated sodium and potassium channels.

iii. The answer is False. The voltage sensor is localized in the first 4 transmembrane regions of domain 1.

iv. The answer is True. The permeability to an ion is increased, then the ion movement will be controlled by concentration gradient.

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