Q: Which formula correctly calculates the osmolarity of a solution containing 0.5 mol/L MgCl$_2$ (which dissociates into 3 particles per molecule)?

$0.5 \text{ mol/L} \times 3 \text{ particles/molecule} = 1.5 \text{ OsM}$

Question 1

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

Accepted Answer

Cholesterol increases membrane viscosity by stabilizing regions and making them less permeable.

Question 2

A solution contains 1 mol/L glucose and 1 mol/L NaCl. Calculate its osmolarity using the formula $	ext{osmolarity} = 	ext{molarity} 	imes 	ext{particles per molecule}$, given that NaCl dissociates into 1.8 particles per molecule in water.

Accepted Answer

$2.8 	ext{ OsM}$

Question 3

Which type of cell membrane protein is most likely to participate in cell signaling and attachment to the cytoskeleton?

Accepted Answer

Peripheral proteins

Question 4

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 follows urea into the cell.

Question 5

Which of the following statements about osmolarity and tonicity is correct?

Accepted Answer

Osmolarity includes all solutes, while tonicity depends only on non-penetrating solutes.

Question 6

If a cell is placed in a solution that is hyposmotic but isotonic, what will happen to the cell?

Accepted Answer

The cell volume will not change because tonicity determines water movement, not osmolarity.

Question 7

Which of the following best explains why penetrating solutes do not contribute to cell volume changes when determining tonicity?

Accepted Answer

Penetrating solutes equilibrate across the membrane, so water movement is not driven by their concentration gradient.

Question 8

Which formula correctly calculates the osmolarity of a solution containing 0.5 mol/L MgCl$_2$ (which dissociates into 3 particles per molecule)?

Accepted Answer

$0.5 	ext{ mol/L} 	imes 3 	ext{ particles/molecule} = 1.5 	ext{ OsM}$

Question 9

Which of the following is a function of the glycocalyx on the cell membrane?

Accepted Answer

Acts as a protective coat and is involved in cell recognition and interaction.

Question 10

A patient receives an intravenous solution that is 280 mOsM NaCl. What is the expected effect on their red blood cells?

Accepted Answer

Cells will remain unchanged because the solution is isotonic and contains non-penetrating solutes.

Question 11

Which statement best describes the difference between osmolarity and osmolality?

Accepted Answer

Osmolarity is osmoles per litre of solution, while osmolality is osmoles per kg of solvent.

Question 12

Which of the following is true regarding lipid rafts in the cell membrane?

Accepted Answer

They are regions with high cholesterol and an abundance of proteins important in cell signaling.

Question 13

A cell is placed in a solution containing 200 mOsM NaCl and 100 mOsM urea. What is the tonicity of the solution?

Accepted Answer

Hypotonic, because only non-penetrating solutes (NaCl) determine tonicity and urea is penetrating.

Question 14

Which of the following best describes the movement of water during osmosis?

Accepted Answer

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

Question 15

Which compartment contains the highest concentration of potassium ions ($K^+$) in the human body?

Accepted Answer

Intracellular fluid (ICF)

Question 16

Which of the following is a correct statement about the selective permeability of the cell membrane?

Accepted Answer

It allows small, nonpolar molecules and water to cross more easily than large or charged molecules.

Question 17

A solution is described as hyperosmotic but hypotonic relative to a cell. Which of the following best explains this observation?

Accepted Answer

The solution contains more total solutes, but most are penetrating and do not affect cell volume.

Question 18

Which of the following is a function of integral membrane proteins?

Accepted Answer

They act as enzymes, receptors, and transporters spanning the membrane.

Cell Membrane Structure and Dynamics: Proteins, Carbohydrates, Osmosis, and Tonicity CM2

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