Q: Which equation correctly represents the electrochemical gradient for an ion?

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

Question 1

Which of the following best explains why most hydrophilic molecules cannot cross the lipid bilayer unaided?

Accepted Answer

The hydrophobic interior of the bilayer repels hydrophilic molecules, preventing their passage.

Question 2

Which of the following molecules would diffuse most rapidly across a pure lipid bilayer?

Accepted Answer

Oxygen ($$O_2)$$

Question 3

A cell is placed in a solution with a higher solute concentration than its cytoplasm. What is the most likely immediate effect on the cell?

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 4

Which of the following best describes the function of the Na$$^+/K$^+$$ pump?

Accepted Answer

It uses ATP to export 3 Na$$^+$$ ions and import 2 K$$^+$$ ions against their concentration gradients.

Question 5

Which equation correctly represents the electrochemical gradient for an ion?

Accepted Answer

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

Question 6

A glucose/Na$$^+$$ symporter in the intestinal epithelium uses which of the following to drive glucose uptake?

Accepted Answer

The electrochemical gradient of Na$$^+$$

Question 7

Which of the following is NOT a function of the plasma membrane?

Accepted Answer

Synthesizing proteins for export

Question 8

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It requires a transport protein but does not require energy input.

Question 9

A cell maintains a resting membrane potential of $$-70 mV. $$Which of the following contributes most to this negative potential?

Accepted Answer

The presence of negatively charged proteins and nucleic acids inside the cell

Question 10

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

Accepted Answer

Channels form hydrophilic pores for specific ions, while transporters bind solutes and undergo conformational changes.

Question 11

Which of the following scenarios would most likely require active transport?

Accepted Answer

Importing Ca$$^{2+}$$ into the sarcoplasmic reticulum against its concentration gradient

Question 12

If a cell's Na$$^+/K$^+$$ pumps are inhibited, what is the most immediate effect on the cell's ion gradients?

Accepted Answer

Na$$^+$$ will accumulate inside the cell and K$$^+$$ will decrease inside the cell.

Question 13

Which of the following best describes the role of the Ca$$^{2+}$$ pump in muscle cells?

Accepted Answer

It actively transports Ca$$^{2+}$$ from the cytosol into the sarcoplasmic reticulum, lowering cytosolic Ca$$^{2+}$$ concentration.

Question 14

Which of the following is a correct example of secondary active transport?

Accepted Answer

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

Question 15

Which of the following would increase the rate of passive diffusion of a molecule across a lipid bilayer?

Accepted Answer

Increasing the molecule's hydrophobicity

Question 16

A patient is given a drug that blocks all ATP production in their cells. Which of the following transport processes would be most immediately affected?

Accepted Answer

Active transport of Na$$^+$$ out of the cell

Question 17

Which of the following best describes the direction of net movement for an uncharged solute during passive transport?

Accepted Answer

From high to low concentration

Question 18

Which of the following is true regarding the osmolarity of a solution?

Accepted Answer

Osmolarity is the total concentration of solute particles in a solution.

Question 19

Which of the following best explains why plant cells do not burst in hypotonic solutions?

Accepted Answer

The rigid cell wall prevents excessive swelling.

Question 20

Which of the following is a direct result of the Na$$^+/K$^+$$ pump activity in animal cells?

Accepted Answer

Generation of a high Na$$^+$$ concentration outside the cell and a high K$$^+$$ concentration inside the cell

Transport Across Cell Membranes: Mechanisms and Principles

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