Question 1

Which of the following best explains why phospholipids spontaneously form bilayers in aqueous environments?

Accepted Answer

Their amphipathic nature, with hydrophilic heads and hydrophobic tails, drives the formation of bilayers.

Question 2

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

Accepted Answer

The solution is hypotonic to the cell.

Question 3

Which of the following molecules would most easily diffuse through a pure phospholipid bilayer without the aid of a transport protein?

Accepted Answer

Oxygen ($\mathrm{O_2}$)

Question 4

A plant cell is placed in a hypertonic solution. What is the most likely outcome?

Accepted Answer

The cell will lose water and undergo plasmolysis.

Question 5

Which of the following statements about the fluid mosaic model is correct?

Accepted Answer

Membrane proteins can move laterally within the bilayer but rarely flip-flop between layers.

Question 6

A patient with familial hypercholesterolemia has defective LDL receptor proteins. Which membrane process is directly impaired in this disease?

Accepted Answer

Receptor-mediated endocytosis

Question 7

Which of the following best describes the function of the sodium-potassium pump in animal cells?

Accepted Answer

It uses ATP to move $3\ \mathrm{Na^+}$ out and $2\ \mathrm{K^+}$ in, maintaining membrane potential.

Question 8

Which of the following is a key difference between facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion does not require energy, while active transport requires ATP.

Question 9

A cell is placed in an unknown solution. After some time, the cell neither swells nor shrinks. What can you conclude about the solution?

Accepted Answer

The solution is isotonic to the cell.

Question 10

Which of the following best explains why cholesterol is considered a 'fluidity buffer' in animal cell membranes?

Accepted Answer

It stabilizes membrane fluidity by preventing extremes of rigidity or fluidity at different temperatures.

Question 11

Which of the following best describes the role of gap junctions in animal cells?

Accepted Answer

They allow direct passage of small molecules and ions between adjacent cells.

Question 12

Which of the following is true regarding the movement of water across a selectively permeable membrane?

Accepted Answer

Water moves from areas of low solute concentration to areas of high solute concentration by osmosis.

Question 13

Which of the following best describes the function of tight junctions in animal tissues?

Accepted Answer

They prevent the passage of materials between adjacent cells.

Question 14

A cell uses exocytosis to secrete a protein hormone. Which of the following best describes this process?

Accepted Answer

Vesicles containing the hormone fuse with the plasma membrane, releasing their contents outside the cell.

Question 15

Which of the following statements about membrane carbohydrates is correct?

Accepted Answer

They function as cell recognition markers and are found on the extracellular side of the plasma membrane.

Question 16

Which of the following best describes the process of signal transduction across a cell membrane?

Accepted Answer

A signaling molecule binds to a receptor, causing a conformational change that transmits information into the cell.

Question 17

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

Accepted Answer

They have hydrophobic regions that interact with the membrane's hydrophobic core.

Question 18

A solution contains $0.2\ \mathrm{mol/L}$ of glucose and $0.1\ \mathrm{mol/L}$ of NaCl. What is the total osmolarity of the solution?

Accepted Answer

$0.4\ \mathrm{osmoles/L}$

Question 19

Which of the following best explains why plant cells do not burst in hypotonic solutions?

Accepted Answer

The cell wall provides structural support and resists excessive water uptake, creating turgor pressure.

Question 20

Which of the following is an example of cotransport in cell membranes?

Accepted Answer

The use of a sodium gradient to drive glucose uptake against its concentration gradient.

Chapter 7: Membranes – Structure and Function (General Biology Study Notes)

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