Question 1

Which of the following best explains why the plasma membrane is described as a 'fluid mosaic'?

Accepted Answer

Because the membrane consists of various proteins embedded in a fluid phospholipid bilayer, allowing lateral movement of components.

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which of the following best describes the tonicity of the solution relative to the cell, and the direction of water movement?

Accepted Answer

The solution is hypotonic; water moves into the cell.

Question 3

Which of the following statements about cholesterol in the plasma membrane is correct?

Accepted Answer

Cholesterol acts as a fluidity buffer, restraining phospholipid movement at high temperatures and preventing tight packing at low temperatures.

Question 4

Which of the following molecules can most easily diffuse across the plasma membrane without the aid of transport proteins?

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 undergo plasmolysis as water leaves and the plasma membrane pulls away from the cell wall.

Question 6

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient through a membrane protein, without energy input.

Question 7

A freshwater protist such as Paramecium uses a contractile vacuole to:

Accepted Answer

Expel excess water that enters by osmosis, maintaining osmotic balance.

Question 8

Which of the following is a function of glycoproteins and glycolipids in the plasma membrane?

Accepted Answer

They serve as the cell's 'fingerprint' for cell-to-cell recognition.

Question 9

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

Accepted Answer

It uses ATP to actively transport Na\^+ out of the cell and K\^+ into the cell, creating an electrochemical gradient.

Question 10

Which of the following statements about membrane potential is correct?

Accepted Answer

Membrane potential is the voltage difference across a membrane, with the inside usually more negative than the outside due to ion distribution.

Question 11

A cell is actively transporting protons (H\^+) out of the cytoplasm, creating a higher concentration of H\^+ outside the cell. This process is an example of:

Accepted Answer

Active transport via a proton pump

Question 12

Which of the following best describes cotransport?

Accepted Answer

The active transport of one solute directly coupled to the passive transport of another solute down its gradient.

Question 13

Which of the following scenarios illustrates the concept of selective permeability of the plasma membrane?

Accepted Answer

Glucose requires a transport protein to enter the cell, while carbon dioxide diffuses directly through the membrane.

Question 14

Which of the following processes requires energy input from the cell?

Accepted Answer

Active transport of sodium ions

Question 15

During receptor-mediated endocytosis, which of the following occurs?

Accepted Answer

Specific molecules bind to receptors on the cell surface, triggering vesicle formation and uptake.

Question 16

A scientist observes that a certain membrane protein spans the entire lipid bilayer and facilitates the movement of ions. This protein is best classified as:

Accepted Answer

A transmembrane (integral) protein

Question 17

Which of the following best explains why membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids?

Accepted Answer

Unsaturated fatty acids have kinks that prevent tight packing of phospholipids.

Question 18

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

Accepted Answer

Synthesis of phospholipids

Question 19

A cell needs to secrete a large quantity of digestive enzymes into the extracellular space. Which process will it most likely use?

Accepted Answer

Exocytosis

Question 20

Which of the following equations best represents the movement of solutes during diffusion?

Accepted Answer

$$J = -D \frac{dC}{dx}$$

Membrane Structure and Function: Chapter 7 Study Guide

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