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

According to the fluid mosaic model, which statement is correct regarding the structure of biological membranes?

Accepted Answer

Membranes consist of a fluid bilayer of phospholipids with proteins embedded or associated, allowing lateral movement of most components.

Question 3

How does cholesterol affect membrane fluidity at different temperatures in animal cells?

Accepted Answer

At high temperatures, cholesterol decreases fluidity by restraining phospholipid movement; at low temperatures, it prevents tight packing and maintains fluidity.

Question 4

A plant cell is placed in a hypertonic solution. What will most likely happen to the cell?

Accepted Answer

Water will leave the cell, causing the plasma membrane to pull away from the cell wall in a process called plasmolysis.

Question 5

Which type of molecule is most likely to diffuse rapidly through the lipid bilayer of a plasma membrane without the aid of a transport protein?

Accepted Answer

Small, nonpolar molecules such as $\mathrm{O_2}$ and $\mathrm{CO_2}$

Question 6

Which of the following best explains why facilitated diffusion does not require energy input from the cell?

Accepted Answer

Molecules move down their concentration gradient through specific transport proteins.

Question 7

A red blood cell is placed in pure water. Which of the following will occur, and why?

Accepted Answer

Water will enter the cell by osmosis, causing it to swell and potentially lyse, because the cell is hypertonic to the solution.

Question 8

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 9

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

Accepted Answer

It uses ATP to move $3\ \mathrm{Na^+}$ ions out of the cell and $2\ \mathrm{K^+}$ ions into the cell, maintaining electrochemical gradients.

Question 10

Which process is responsible for the uptake of cholesterol into animal cells, and what is a potential consequence if this process is defective?

Accepted Answer

Receptor-mediated endocytosis; defective receptors can lead to high blood cholesterol and increased risk of heart disease.

Question 11

Which of the following statements about membrane proteins is correct?

Accepted Answer

Integral proteins span the membrane and often function as channels or transporters.

Question 12

A cell is placed in a solution and water moves into the cell, causing it to swell. 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 13

Which of the following best explains why plant cells do not burst when placed in a hypotonic solution?

Accepted Answer

The rigid cell wall exerts turgor pressure, preventing excessive swelling.

Question 14

Which of the following is an example of active transport?

Accepted Answer

The movement of $\mathrm{Na^+}$ ions out of a cell against their concentration gradient using ATP.

Question 15

Which of the following best describes the process of exocytosis?

Accepted Answer

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

Question 16

A patient with familial hypercholesterolemia has high levels of cholesterol in the blood. Which cellular process is most likely defective in this patient?

Accepted Answer

Receptor-mediated endocytosis of LDL particles.

Question 17

Which of the following best explains why ions such as $\mathrm{Na^+}$ and $\mathrm{K^+}$ require transport proteins to cross the plasma membrane?

Accepted Answer

The hydrophobic core of the lipid bilayer repels charged particles, preventing their diffusion.

Question 18

Which of the following scenarios best illustrates cotransport in biological membranes?

Accepted Answer

The active transport of $\mathrm{H^+}$ out of a plant cell creates a gradient that drives the uptake of sucrose into the cell via a cotransporter.

Question 19

Which of the following statements about osmoregulation is correct?

Accepted Answer

Organisms living in hypotonic environments, such as Paramecium, use contractile vacuoles to expel excess water.

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

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