Question 1

Which of the following best describes the main difference between facilitated diffusion and active transport across a cell membrane?

Accepted Answer

Facilitated diffusion moves solutes down their concentration gradient without energy input, while active transport moves solutes against their gradient using energy.

Question 2

A patient with severe diarrhea is treated with a solution containing both salt ($$\mathrm{NaCl}) $$and glucose. Which cellular mechanism explains why this treatment is effective in reducing dehydration?

Accepted Answer

Salt and glucose are absorbed by cotransporters, which increases solute uptake and water follows by osmosis.

Question 3

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

Accepted Answer

It moves three $$\mathrm{Na^+}$$ ions out of the cell and two $$\mathrm{K^+}$$ ions into the cell per cycle, using ATP.

Question 4

What is the primary role of ATP in the function of the sodium-potassium pump?

Accepted Answer

ATP hydrolysis provides energy by transferring a phosphate group to the pump, causing a conformational change.

Question 5

A nerve cell at rest has a negative membrane potential. Which of the following best explains why the inside of the cell is negative relative to the outside?

Accepted Answer

The sodium-potassium pump moves more positive charges out than in, creating a net negative charge inside.

Question 6

Which of the following best describes the electrochemical gradient?

Accepted Answer

It is the combined effect of the ion’s concentration gradient and the membrane potential on ion movement.

Question 7

In plant cells, which process allows the uptake of sucrose against its concentration gradient?

Accepted Answer

Cotransport with protons ($$\mathrm{H^+}) $$moving down their gradient.

Question 8

Which of the following is a direct result of the action of an electrogenic pump such as the sodium-potassium pump?

Accepted Answer

Generation of a voltage difference (membrane potential) across the membrane.

Question 9

A mutation causes a carrier protein in the plasma membrane to lose its ability to bind ATP. Which process would be most directly affected?

Accepted Answer

Active transport of ions against their concentration gradients.

Question 10

Which of the following scenarios best illustrates cotransport in animal cells?

Accepted Answer

Glucose is transported into intestinal cells along with sodium ions ($$\mathrm{Na^+}) $$moving down their gradient.

Question 11

Which of the following best explains why the sodium-potassium pump is considered an electrogenic pump?

Accepted Answer

It generates a net movement of positive charge out of the cell, creating a voltage difference.

Question 12

A plant cell is unable to maintain a proton gradient across its plasma membrane. Which process would be most directly impaired?

Accepted Answer

Cotransport of sucrose into the cell.

Question 13

Which of the following is true about the movement of ions across a membrane?

Accepted Answer

Ions move according to both their concentration gradient and the membrane potential (electrochemical gradient).

Question 14

Which of the following would you expect to find in the lysosomal membrane to maintain its acidic environment?

Accepted Answer

Proton pumps that use ATP to transport $$\mathrm{H^+}$$ ions into the lysosome.

Question 15

Which of the following best describes the role of carrier proteins in active transport?

Accepted Answer

They use energy to move solutes against their concentration gradient.

Question 16

A cell is placed in a solution with a high concentration of potassium ions ($$\mathrm{K^+}) $$and a low concentration of sodium ions ($$\mathrm{Na^+}). $$Which process allows the cell to maintain higher internal $$\mathrm{K^+}$$ and lower internal $$\mathrm{Na^+}$$ than the environment?

Accepted Answer

Active transport by the sodium-potassium pump using ATP.

Question 17

Which of the following is a real-life application of understanding cotransport mechanisms in medicine?

Accepted Answer

Using oral rehydration therapy with salt and glucose to treat dehydration from diarrhea.

Question 18

Which of the following best explains why facilitated diffusion does not require energy?

Accepted Answer

It moves solutes down their concentration gradient through transport proteins.

Question 19

A scientist blocks all ATP production in a cell. Which of the following processes would be most immediately affected?

Accepted Answer

Active transport of sodium and potassium ions.

Question 20

Which of the following is NOT a function of electrogenic pumps in cells?

Accepted Answer

Facilitating the passive diffusion of hydrophobic molecules.

Active Transport and Membrane Potential: Mechanisms of Solute Movement Across Biological Membranes

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