Q: The sodium-potassium pump moves ions against their concentration gradients. Which of the following best describes the stoichiometry of ions transported per ATP hydrolyzed?

3 Na\textsuperscript{+} out, 2 K\textsuperscript{+} in

Q: Which of the following best explains why the sodium-potassium pump is essential for maintaining the resting membrane potential?

It actively transports Na\textsuperscript{+} out and K\textsuperscript{+} in, maintaining concentration gradients.

Q: If a cell is placed in a solution with a much higher concentration of Na\textsuperscript{+} than its cytosol, what will happen to Na\textsuperscript{+} ions if sodium channels open?

Na\textsuperscript{+} will move into the cell.

Q: Which of the following would occur if the concentration gradient for K\textsuperscript{+} across the membrane was eliminated?

There would be no net movement of K\textsuperscript{+}.

Question 1

Which of the following best describes the direction of movement for potassium ions (K	extsuperscript{+}) through a leak channel in a neuron at rest, considering both the electrical and concentration gradients?

Accepted Answer

The concentration gradient favors movement out of the cell, while the electrical gradient favors movement into the cell.

Question 2

Given the following concentrations: extracellular Na	extsuperscript{+} = 145 mM, intracellular Na	extsuperscript{+} = 15 mM, which direction will the concentration gradient drive sodium ions (Na	extsuperscript{+})?

Accepted Answer

From outside the cell to inside the cell.

Question 3

Which equation best represents the net electrochemical gradient ($$E_{net}) $$for an ion across a membrane?

Accepted Answer

$$E_{net} = E_{chemical} + E_{electrical}$$

Question 4

A patient is given a drug that blocks the sodium-potassium pump (Na	extsuperscript{+}/K	extsuperscript{+}-ATPase). What is the most likely effect on intracellular sodium concentration?

Accepted Answer

It will increase.

Question 5

Which of the following is TRUE regarding the standard concentrations of sodium and potassium ions in a typical neuron at rest?

Accepted Answer

Sodium concentration is higher outside the cell; potassium concentration is higher inside.

Question 6

The sodium-potassium pump moves ions against their concentration gradients. Which of the following best describes the stoichiometry of ions transported per ATP hydrolyzed?

Accepted Answer

3 Na	extsuperscript{+} out, 2 K	extsuperscript{+} in

Question 7

If the extracellular fluid has a chloride (Cl	extsuperscript{--}) concentration of 120 mM and the cytosol has 60 mM, which gradient favors movement of Cl	extsuperscript{--} into the cell?

Accepted Answer

The concentration gradient only.

Question 8

Which of the following statements about the sodium-potassium pump is CORRECT?

Accepted Answer

It requires ATP to function.

Question 9

A neuron at rest has a membrane potential of $$-70 mV. $$Which force opposes the movement of K	extsuperscript{+} out of the cell?

Accepted Answer

The electrical gradient.

Question 10

Which of the following best explains why the sodium-potassium pump is essential for maintaining the resting membrane potential?

Accepted Answer

It actively transports Na	extsuperscript{+} out and K	extsuperscript{+} in, maintaining concentration gradients.

Question 11

If a cell is placed in a solution with a much higher concentration of Na	extsuperscript{+} than its cytosol, what will happen to Na	extsuperscript{+} ions if sodium channels open?

Accepted Answer

Na	extsuperscript{+} will move into the cell.

Question 12

Which formula correctly expresses the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a monovalent cation?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$$

Question 13

Which of the following would occur if the concentration gradient for K	extsuperscript{+} across the membrane was eliminated?

Accepted Answer

There would be no net movement of K	extsuperscript{+}.

Question 14

A mutation causes the sodium-potassium pump to transport only Na	extsuperscript{+} ions. What is the most likely consequence for the cell?

Accepted Answer

The cell will lose its ability to maintain resting membrane potential.

Question 15

Which of the following is a direct result of the sodium-potassium pump's activity?

Accepted Answer

The cell maintains a negative resting membrane potential.

Question 16

If the sodium-potassium pump is inhibited, which of the following will happen to the gradients of Na	extsuperscript{+} and K	extsuperscript{+} over time?

Accepted Answer

Both gradients will dissipate.

Question 17

Which of the following best describes the role of ATP in the function of the sodium-potassium pump?

Accepted Answer

ATP provides the energy to move ions against their gradients.

Question 18

A cell is exposed to a toxin that increases membrane permeability to Na	extsuperscript{+}. What is the most likely effect on the cell's membrane potential?

Accepted Answer

The membrane potential will become less negative (depolarize).

Electrochemical Gradients and the Sodium-Potassium Pump in Cellular Physiology

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