Question 1

Which statement best describes the difference between osmotic equilibrium and chemical equilibrium in the context of body fluid compartments?

Accepted Answer

Osmotic equilibrium refers to equal water movement across compartments, while chemical disequilibrium means solute concentrations differ between compartments.

Question 2

A patient receives an intravenous solution containing 0.9% NaCl. Which statement best explains why this solution is considered isotonic to red blood cells?

Accepted Answer

Because NaCl is a nonpenetrating solute, and its concentration does not cause net water movement into or out of the cells.

Question 3

Given a solution containing 250 mOsm/L NaCl (nonpenetrating) and 250 mOsm/L urea (penetrating), what is the tonicity of this solution relative to a cell with 300 mOsm/L nonpenetrating solutes?

Accepted Answer

Hypotonic

Question 4

Which equation correctly expresses osmolarity in terms of solute and volume?

Accepted Answer

$C = \frac{S}{V}$

Question 5

A cell is placed in a solution with a higher concentration of nonpenetrating solutes than the cell's cytoplasm. What will happen to the cell?

Accepted Answer

It will shrink due to water efflux.

Question 6

Which of the following best describes the role of aquaporins in osmosis?

Accepted Answer

They allow water to move passively across the membrane in response to solute concentration gradients.

Question 7

Which of the following is true regarding the sodium-potassium pump (Na+-K+-ATPase)?

Accepted Answer

It uses ATP to move Na+ out of the cell and K+ into the cell against their concentration gradients.

Question 8

Which formula is used to calculate the equilibrium potential for an ion across a membrane?

Accepted Answer

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

Question 9

A cell membrane is selectively permeable to K+ but not to anions. What is the immediate effect of opening K+ leak channels?

Accepted Answer

K+ will move out of the cell, making the inside more negative.

Question 10

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It moves molecules down their concentration gradient using carrier proteins.

Question 11

If a solution is hyposmotic to a cell, what can you conclude about its tonicity?

Accepted Answer

It is always hypotonic.

Question 12

Which of the following is a property of simple diffusion across a cell membrane?

Accepted Answer

It is dependent on the solubility of the molecule in lipids.

Question 13

A cell is placed in a solution containing only penetrating solutes. What will happen to the cell at equilibrium?

Accepted Answer

It will remain the same size.

Question 14

Which of the following best explains why glucose solutions can be isosmotic but hypotonic to cells?

Accepted Answer

Glucose is a penetrating solute, so it enters the cell and does not contribute to tonicity.

Question 15

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

Accepted Answer

Directly synthesizing ATP from glucose.

Question 16

Which type of membrane channel opens in response to changes in membrane potential?

Accepted Answer

Voltage-gated channel

Question 17

Which process describes the movement of substances across a cell by endocytosis, vesicular transport, and exocytosis?

Accepted Answer

Transcytosis

Question 18

Which of the following best describes the resting membrane potential of most human cells?

Accepted Answer

It is about -70 mV, mainly due to K+ leak channels.

Question 19

Which of the following is true about the electrochemical gradient?

Accepted Answer

It is the combination of electrical and concentration gradients that determines ion movement.

Membrane Dynamics: Osmosis, Tonicity, and Membrane Transport in Human Physiology

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