Question 1

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A flexible boundary formed by a double layer of phospholipids with proteins, cholesterol, and carbohydrates scattered throughout, allowing lateral movement.

Question 2

What is the primary function of cholesterol in the plasma membrane at moderate temperatures?

Accepted Answer

It reduces the movement of phospholipids, helping to maintain membrane fluidity.

Question 3

Which part of a phospholipid is hydrophilic?

Accepted Answer

The phosphate head group

Question 4

A cell is placed in a solution containing a high concentration of oxygen. By which process will oxygen most likely enter the cell?

Accepted Answer

Simple diffusion

Question 5

Which of the following molecules would most likely require a channel protein to cross the plasma membrane?

Accepted Answer

Glucose

Question 6

What is the main difference between facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion moves solutes down their concentration gradient without energy input, while active transport moves solutes against the gradient using energy.

Question 7

Which equation best represents the movement of solutes by simple diffusion across the plasma membrane?

Accepted Answer

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

Question 8

A neuron uses the sodium-potassium pump to maintain its resting potential. Which type of membrane transport is this an example of?

Accepted Answer

Active transport

Question 9

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

Accepted Answer

They stick out of the outer part of the membrane and are attached to proteins or lipids, aiding in cell recognition.

Question 10

Which of the following best describes the process of endocytosis?

Accepted Answer

The cell takes in materials by engulfing them with the plasma membrane to form a vesicle.

Question 11

Which of the following is true about the movement of proteins within the plasma membrane?

Accepted Answer

Proteins can move laterally within the bilayer, forming microdomains.

Question 12

A cell is exposed to a toxin that blocks aquaporin channels. What is the most likely effect?

Accepted Answer

Water movement across the membrane will decrease significantly.

Question 13

Which of the following is NOT a component of the plasma membrane according to the fluid mosaic model?

Accepted Answer

Cellulose fibers

Question 14

Which process requires energy input from ATP to move molecules across the plasma membrane?

Accepted Answer

Active transport

Question 15

Which of the following best explains why ions cannot easily cross the plasma membrane by simple diffusion?

Accepted Answer

Ions are charged and cannot pass through the hydrophobic core of the membrane.

Question 16

Which of the following is a correct description of exocytosis?

Accepted Answer

Vesicles fuse with the plasma membrane to release their contents outside the cell.

Question 17

Which of the following is an amphipathic molecule found in the plasma membrane?

Accepted Answer

Phospholipid

Question 18

A mutation causes a cell to produce a defective sodium-potassium pump. What is the most likely consequence?

Accepted Answer

The cell will be unable to maintain its ion gradients, affecting nerve impulse transmission.

Question 19

Which of the following best describes the orientation of phospholipids in the plasma membrane?

Accepted Answer

Hydrophilic heads face outward toward the aqueous environment, while hydrophobic tails face inward, shielded from water.

Question 20

Which of the following is a real-world example of facilitated diffusion?

Accepted Answer

Glucose entering muscle cells via a specific transporter protein.

Plasma Membrane Structure and Transport Mechanisms: The Fluid Mosaic Model

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