Question 1

Which of the following ions has the highest extracellular concentration in a typical mammalian cell, according to Table 11-1?

Accepted Answer

Na$$^+$$

Question 2

A protein-free lipid bilayer is most permeable to which type of molecule?

Accepted Answer

Hydrophobic molecules

Question 3

Which of the following best describes the mechanism of a transporter protein during passive transport?

Accepted Answer

It binds solutes and undergoes conformational changes to move them across the membrane.

Question 4

Which equation best represents the rate of transporter-mediated diffusion as shown in the kinetic graph?

Accepted Answer

$$v = V_{max} \frac{[S]}{K_m + [S]}$$

Question 5

Which of the following is NOT a method used by cells to drive active transport across membranes?

Accepted Answer

Simple diffusion

Question 6

In the Na$$^+-K$^+$$ pump, how many Na$$^+$$ ions are transported out of the cell for every ATP hydrolyzed?

Accepted Answer

3

Question 7

Which of the following best explains why aquaporins are selective for water molecules?

Accepted Answer

They contain specific amino acids (Asn) that form hydrogen bonds with water, preventing passage of ions.

Question 8

A patient has a mutation in a gene encoding a channel protein that is always open. Which of the following is a likely consequence?

Accepted Answer

The cell will lose its ability to regulate ion flow, potentially leading to depolarization.

Question 9

Which of the following statements about the electrochemical gradient is correct?

Accepted Answer

It is the sum of the concentration gradient and the membrane potential.

Question 10

In intestinal epithelial cells, which transporter is responsible for the initial uptake of glucose from the gut lumen?

Accepted Answer

Na$$^+-$$driven glucose symport

Question 11

Which of the following is a characteristic of channel-mediated transport compared to transporter-mediated transport?

Accepted Answer

Channel-mediated transport allows rapid movement of solutes without binding.

Question 12

Which of the following best describes the function of ABC transporters?

Accepted Answer

They use ATP hydrolysis to transport small molecules across membranes.

Question 13

If the extracellular concentration of K$$^+$$ drops from 5 mM to 1 mM, what effect would this have on the membrane potential?

Accepted Answer

The membrane potential would become more negative (hyperpolarized).

Question 14

Which of the following is true regarding the permeability of the synthetic lipid bilayer to ions?

Accepted Answer

Ions require specific transport proteins to cross the bilayer.

Question 15

A cell is exposed to a toxin that inhibits ATP production. Which transport process would be most directly affected?

Accepted Answer

ATP-driven ion pumps

Question 16

Which of the following best describes the difference between symport and antiport mechanisms?

Accepted Answer

Symport moves two molecules in the same direction; antiport moves them in opposite directions.

Question 17

Which of the following molecules would have the highest permeability across a protein-free lipid bilayer?

Accepted Answer

CO$$_2$$

Question 18

Which of the following is a consequence of the Na$$^+-K$^+$$ pump activity in animal cells?

Accepted Answer

It maintains a high intracellular K$$^+$$ concentration.

Question 19

Which of the following is a real-world example of coupled transport in human physiology?

Accepted Answer

Na$$^+-$$driven glucose symport in intestinal epithelial cells

Small-Molecule Transport and Electrical Properties of Membranes

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