Question 1

Which of the following best describes the amphipathic nature of phospholipids in the plasma membrane?

Accepted Answer

They have both hydrophilic heads and hydrophobic tails, allowing them to form a bilayer with tails facing inward and heads facing outward.

Question 2

A red blood cell is placed in a solution and swells until it bursts. Which of the following best explains what type of solution the cell was placed in and the direction of water movement?

Accepted Answer

The cell was placed in a hypotonic solution, and water moved into the cell.

Question 3

Which of the following statements about membrane fluidity is correct?

Accepted Answer

At low temperatures, membranes with a higher proportion of unsaturated fatty acids remain more fluid than those with more saturated fatty acids.

Question 4

Which of the following molecules is most likely to diffuse directly through the lipid bilayer of a plasma membrane without the aid of a transport protein?

Accepted Answer

Oxygen ($O_2$)

Question 5

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

Accepted Answer

The cell will lose water, and the plasma membrane will pull away from the cell wall (plasmolysis).

Question 6

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

Accepted Answer

It uses ATP to move $3$ $Na^+$ ions out of the cell and $2$ $K^+$ ions into the cell, maintaining the electrochemical gradient.

Question 7

Which of the following is a function of membrane carbohydrates?

Accepted Answer

They serve as markers for cell recognition, often attached to proteins (glycoproteins) or lipids (glycolipids).

Question 8

Which of the following best explains why ions such as $Na^+$ and $Cl^-$ cannot easily cross the plasma membrane without assistance?

Accepted Answer

The hydrophobic interior of the lipid bilayer repels charged and polar molecules.

Question 9

A cell is placed in an isotonic solution. Which of the following best describes the movement of water?

Accepted Answer

Water moves in and out of the cell at equal rates, resulting in no net change in cell volume.

Question 10

Which of the following is an example of active transport?

Accepted Answer

The movement of $K^+$ ions into a cell against their concentration gradient using ATP.

Question 11

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

It is a process in which specific molecules bind to receptors on the cell surface, triggering vesicle formation to bring those molecules into the cell.

Question 12

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It requires transport proteins but does not require energy, and moves substances down their concentration gradient.

Question 13

A patient with familial hypercholesterolemia has high blood cholesterol because:

Accepted Answer

Their cells lack functional LDL receptor proteins, preventing cholesterol uptake by receptor-mediated endocytosis.

Question 14

Which of the following best explains the role of cholesterol in animal cell membranes at different temperatures?

Accepted Answer

At high temperatures, cholesterol restrains phospholipid movement, reducing fluidity; at low temperatures, it prevents tight packing, maintaining fluidity.

Question 15

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

Accepted Answer

They penetrate the hydrophobic core of the lipid bilayer and often span the entire membrane.

Question 16

Which of the following best describes cotransport (secondary active transport) in plant cells?

Accepted Answer

The downhill diffusion of $H^+$ ions is coupled to the active transport of sucrose into the cell.

Question 17

Which of the following scenarios best illustrates the concept of selective permeability?

Accepted Answer

A cell allows $O_2$ and $CO_2$ to diffuse freely, but requires transport proteins for glucose and ions.

Question 18

Which of the following best explains why plant cells become turgid in a hypotonic solution?

Accepted Answer

Water enters the cell, causing it to swell until the cell wall exerts turgor pressure, preventing further expansion.

Question 19

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

Accepted Answer

Serving as the main energy source for the cell.

Membrane Structure and Function: Study Notes (Campbell Biology, Chapter 7)

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