Q: Which equation correctly calculates the osmolarity of a 1 mol/L NaCl solution, given that NaCl dissociates into Na⁺ and Cl⁻ ions, but only 90% of the molecules dissociate at body temperature?

$$1 \times 1.9 = 1.9$$ osmol/L$$\ (1 \text{ mol/L} \times 1.9 \text{ particles/molecule})$$

Question 1

Which of the following best describes the function of lipid rafts in the cell membrane?

Accepted Answer

They are regions with high cholesterol and sphingolipid content that organize proteins important for cell signaling.

Question 2

A red blood cell is placed in a 300 mOsM solution of urea. What will happen to the cell and why?

Accepted Answer

The cell will swell because urea is a penetrating solute and water will follow urea into the cell.

Question 3

Which equation correctly calculates the osmolarity of a 1 mol/L NaCl solution, given that NaCl dissociates into Na⁺ and Cl⁻ ions, but only 90% of the molecules dissociate at body temperature?

Accepted Answer

$$1 	imes 1.9 = 1.9$$ osmol/L$$\ (1 	ext{ mol/L} 	imes 1.9 	ext{ particles/molecule})$$

Question 4

Which of the following statements best distinguishes between osmolarity and tonicity?

Accepted Answer

Osmolarity measures the total concentration of solute particles, while tonicity describes the effect of a solution on cell volume.

Question 5

A cell is placed in a solution containing 200 mOsM NaCl (non-penetrating) and 100 mOsM glucose (penetrating). What is the tonicity of the solution?

Accepted Answer

Hypotonic, because only non-penetrating solutes determine tonicity and the total is less than the cell's ICF.

Question 6

Which of the following best explains why osmotic equilibrium does not mean chemical equilibrium in body compartments?

Accepted Answer

Water concentrations are equal, but solute concentrations differ between compartments.

Question 7

Which type of membrane protein is most likely to be involved in cell-to-cell recognition and interaction?

Accepted Answer

Glycoproteins

Question 8

A patient receives an intravenous solution that is isosmotic but contains a high concentration of penetrating solutes. What is the likely effect on the patient's red blood cells?

Accepted Answer

The cells will swell as the penetrating solutes enter the cells and water follows.

Question 9

Which of the following best describes the role of cholesterol in the cell membrane?

Accepted Answer

It increases membrane viscosity and stabilizes membrane structure.

Question 10

Calculate the osmolarity of a solution containing 0.5 mol/L MgCl$$_2 ($$which dissociates completely into Mg$$^{2+}$$ and 2 Cl$$^-$$ ions).

Accepted Answer

$$0.5 	imes 3 = 1.5$$ osmol/L

Question 11

Which of the following is a key difference between integral and peripheral membrane proteins?

Accepted Answer

Integral proteins span the membrane, while peripheral proteins are attached to the membrane surface.

Question 12

A cell is placed in a 400 mOsM NaCl solution. What will happen to the cell and why?

Accepted Answer

The cell will shrink because the solution is hypertonic due to non-penetrating NaCl.

Question 13

Which of the following best describes the function of the glycocalyx?

Accepted Answer

It provides a protective coat and is involved in cell recognition and interaction.

Question 14

Which of the following statements about osmosis is correct?

Accepted Answer

Water moves from a region of low solute concentration to a region of high solute concentration.

Question 15

Which of the following best explains why osmolarity and osmolality are nearly identical in the human body?

Accepted Answer

Because the concentrations of solutes are low and the density of water is close to 1 kg/L.

Question 16

A solution contains 150 mM NaCl and 100 mM urea. What is the total osmolarity of the solution?

Accepted Answer

$$150 	imes 2 + 100 	imes 1 = 400$$ mOsm/L

Question 17

Which of the following is true regarding the distribution of ions in body fluid compartments?

Accepted Answer

Na$$^+ is $$higher in the extracellular fluid, while K$$^+ is $$higher in the intracellular fluid.

Question 18

Which of the following best describes the effect of a hypertonic solution on a typical animal cell?

Accepted Answer

The cell will lose water and shrink.

Question 19

Which of the following is a characteristic of aquaporin channels?

Accepted Answer

They facilitate the rapid movement of water across the cell membrane.

Cell Membrane Structure, Composition, and Dynamics

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