ScienceBiologyChapter 11: Resting Membrane Potential
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Chapter 11: Resting Membrane Potential

Violetta Washington avatar Violetta Washington
25 July 2022
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question
Resting Membrane Potential
answer
The Na+ concentration is higher outside of the cell, while the concentration of K+ is higher inside the cell.
question
Which choice best characterizes K+ leak channels?
answer
Transmembrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy.
question
Assume you have a membrane with only potassium leak channels. The RMP is -90mV. Predict the RMP if we add Na+ leak channels. The most likely RMP value of Na+ is ___________.
answer
-70 mV
question
Imagine that the cell membrane from the previous problem becomes more permeable to Na+. Predict how this will affect the RMP.
answer
The RMP will be more positive.
question
Complete the following sentence. The operation of the Na+ -K+ ATPase pump ___________.
answer
Moves 3 Na+ to the ECF and 2 K+ to the cytoplasm. The pumps move more Na+ than K+, which counteracts the effect of the membrane's being more permeable to K+ (more K+ leak channels than Na+).
question
You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of -70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that Na+ and K+ are the major determinants of RMP in this cell, which of the following could best explain your results?
answer
The cell's Na+ -K+ ATPase pumps have stopped functioning. Since the RMP eventually becomes zero, the concentration of ions on either side of membrane would be roughly equal. Without active processes to maintain concentration gradients, we would expect the concentration of ions on either side of the membrane to equilibrate.
question
Cl- is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl- gated channels are suddenly opened.
answer
A more negative RMP would result. Cl- is negatively charged and has a higher concentration in the ECF. The opening of Cl- channels would allow more negative charge to attempt to enter the cytoplasm. If the cell's normal RMP were -70mV, it would now become more negative. The farther away the RMP is from zero, either in the positive or in the negative direction, the greater the separation of charges is. This is called hyperpolarization. When the RMP moves closer to 0 mV, depolarization occurs.