Q: Which of the following equations correctly represents the electrochemical gradient for an ion across a membrane?

$$\\Delta G = RT \\ln \\left( \\frac{[C]_i}{[C]_o} \\right) + zF \\Delta V$$

Question 1

Which of the following molecules is most likely to diffuse freely across a synthetic lipid bilayer without the aid of a transport protein?

Accepted Answer

O$$_2$$

Question 2

A cell is placed in a solution containing a high concentration of K$$^+$$ and a low concentration of Na$$^+. $$Which transport protein is primarily responsible for maintaining the typical mammalian intracellular concentrations of these ions?

Accepted Answer

Na$$^+/K$^+$$ ATPase pump

Question 3

Which of the following best describes the difference between a transporter and a channel protein?

Accepted Answer

Transporters bind specific solutes and undergo conformational changes, while channels form pores and are less specific.

Question 4

Which of the following is an example of secondary active transport?

Accepted Answer

Glucose/Na$$^+$$ symporter using the Na$$^+$$ gradient to import glucose

Question 5

A patient is found to have cancer cells that are resistant to multiple chemotherapeutic drugs. Which membrane protein is most likely overexpressed in these cells?

Accepted Answer

ABC transporter (MDR protein)

Question 6

Which of the following best explains why the resting membrane potential of a typical mammalian cell is negative?

Accepted Answer

The plasma membrane is more permeable to K$$^+$$ than to Na$$^+$$, allowing K$$^+ to $$leave the cell, leaving behind negative charges.

Question 7

Which of the following equations correctly represents the electrochemical gradient for an ion across a membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[C]_i}{[C]_o} \right) + zF \Delta V$$

Question 8

A mutation in a voltage-gated Na$$^+$$ channel causes it to remain open longer than normal. What is the most likely effect on the action potential in a neuron?

Accepted Answer

The action potential will be prolonged, with a delayed repolarization phase.

Question 9

Which of the following best describes the function of myelin sheaths in vertebrate neurons?

Accepted Answer

They insulate the axon, allowing action potentials to jump between nodes of Ranvier (saltatory conduction).

Question 10

Which of the following scenarios is an example of antiport coupled transport?

Accepted Answer

A Ca$$^{2+}/Na$^+$$ exchanger that moves Ca$$^{2+}$$ out of the cell while moving Na$$^+ in$$

Question 11

Which of the following statements about aquaporins is correct?

Accepted Answer

They allow the rapid passive movement of water molecules across the membrane.

Question 12

A researcher adds a drug that blocks ATP synthesis in a cell. Which of the following transport processes would be most directly affected?

Accepted Answer

Na$$^+/K$^+$$ ATPase pump activity

Question 13

Which of the following best explains why Cl$$^-$$ ions do not freely cross the plasma membrane?

Accepted Answer

Cl$$^-$$ ions are charged and cannot pass through the hydrophobic core of the lipid bilayer without a channel or transporter.

Question 14

Which of the following is a key feature of ABC transporters?

Accepted Answer

They hydrolyze ATP to transport a wide variety of molecules across membranes.

Question 15

During the propagation of an action potential, which event occurs immediately after the peak depolarization?

Accepted Answer

Voltage-gated K$$^+$$ channels open, allowing K$$^+ to $$exit the cell.

Question 16

Which of the following best describes the role of the selectivity filter in an ion channel?

Accepted Answer

It determines which ions can pass through the channel based on size and charge.

Question 17

A cell is exposed to a toxin that specifically blocks ligand-gated ion channels at the neuromuscular junction. What is the most likely immediate effect?

Accepted Answer

Muscle contraction will be inhibited due to failure of synaptic transmission.

Question 18

Which of the following best describes the process of saltatory conduction?

Accepted Answer

Action potentials jump from one node of Ranvier to the next, increasing conduction speed.

Question 19

Which of the following is true regarding the concentration of Ca$$^{2+} in a $$typical mammalian cell?

Accepted Answer

Cytoplasmic Ca$$^{2+}$$ concentration is much lower than extracellular concentration.

Membrane Transport of Small Molecules and the Electrical Properties of Membranes

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