Question 1

Which of the following best describes the difference between osmolarity and tonicity?

Accepted Answer

Osmolarity is a measurable value that compares the total number of solute particles in two solutions, while tonicity describes the effect of a solution on cell volume and depends only on nonpenetrating solutes.

Question 2

A patient receives an intravenous solution of 0.45% NaCl. Based on its osmolarity and tonicity, what will happen to the patient’s red blood cells?

Accepted Answer

The cells will swell because the solution is hypotonic.

Question 3

Which of the following is TRUE regarding the distribution of ions across the cell membrane?

Accepted Answer

The concentration of Cl$$^- is $$higher in the extracellular fluid than in the intracellular fluid.

Question 4

Which equation is used to calculate the equilibrium potential for a single ion across a membrane?

Accepted Answer

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

Question 5

A cell is placed in a solution containing 1 OsM glucose and 1 OsM NaCl. The cell membrane is impermeable to NaCl but permeable to glucose. What will happen to the cell?

Accepted Answer

The cell will shrink because the solution is hypertonic.

Question 6

Which of the following best explains why water moves freely across cell membranes?

Accepted Answer

Water moves through specialized protein channels called aquaporins.

Question 7

Which of the following statements about facilitated diffusion is CORRECT?

Accepted Answer

Facilitated diffusion uses carrier proteins to move molecules down their concentration gradient.

Question 8

A cell is placed in a solution and swells until it bursts. Which of the following best describes the solution?

Accepted Answer

The solution is hypotonic to the cell.

Question 9

Which of the following factors will INCREASE the rate of diffusion across a cell membrane according to Fick’s Law?

Accepted Answer

Increasing the membrane permeability

Question 10

Which of the following best describes the function of the sodium-potassium pump (Na$$^+-K$^+-$$ATPase) in maintaining membrane potential?

Accepted Answer

It moves 3 Na$$^+$$ out of the cell and 2 K$$^+$$ into the cell for each ATP hydrolyzed.

Question 11

A patient with severe diarrhea loses 1.1 lbs of body weight. Approximately how much fluid should be replaced to restore homeostasis?

Accepted Answer

500 mL

Question 12

Which of the following is a property of carrier-mediated transport but NOT simple diffusion?

Accepted Answer

Saturation at high substrate concentrations

Question 13

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

Accepted Answer

Na$$^+-$$glucose symporter (SGLT)

Question 14

Which of the following best describes the effect of increasing temperature on the rate of diffusion?

Accepted Answer

The rate of diffusion increases.

Question 15

Which of the following is TRUE about the resting membrane potential of most cells?

Accepted Answer

It is established mainly by K$$^+$$ leak channels and the Na$$^+-K$^+-$$ATPase.

Question 16

Which of the following best describes the process of transcytosis?

Accepted Answer

Movement of molecules across an epithelium via endocytosis, vesicular transport, and exocytosis

Question 17

Which of the following is a correct statement about the effect of a hyperosmotic solution on a cell?

Accepted Answer

A hyperosmotic solution can be hypotonic, isotonic, or hypertonic depending on the concentration of nonpenetrating solutes.

Question 18

Which of the following is a property of open (leak) channels in the cell membrane?

Accepted Answer

They allow ions to move back and forth without regulation.

Question 19

Which of the following best explains why the inside of a resting cell is negative relative to the outside?

Accepted Answer

There are more negative ions inside the cell and the membrane is more permeable to K$$^+$$ than Na$$^+.$$

Membrane Dynamics: Osmosis, Tonicity, and Transport Mechanisms

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