Question 1

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

Accepted Answer

A fluid structure with a mosaic of proteins embedded in or attached to a double layer (bilayer) of phospholipids.

Question 2

Which component of the plasma membrane is primarily responsible for its selective permeability?

Accepted Answer

Phospholipid bilayer

Question 3

A red blood cell is placed in a hypotonic solution. Which process will occur, and what is the likely outcome for the cell?

Accepted Answer

Osmosis; the cell will swell and may burst.

Question 4

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Cholesterol acts as a fluidity buffer, maintaining membrane fluidity across temperature changes.

Question 5

Which equation best represents the net movement of water across a selectively permeable membrane due to osmosis?

Accepted Answer

$$J = -L_p (\Delta P - \sigma \Delta \pi)$$

Question 6

A cell uses ATP to move sodium ions against their concentration gradient. Which process is this an example of?

Accepted Answer

Active transport

Question 7

Which of the following would most likely increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Adding more cholesterol to the membrane

Question 8

Which type of membrane protein is most likely to function as a channel for hydrophilic substances?

Accepted Answer

Integral transmembrane protein

Question 9

A patient receives a blood transfusion with the wrong blood type. Which membrane component is most directly responsible for the immune reaction?

Accepted Answer

Glycoproteins

Question 10

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

Accepted Answer

Energy storage

Question 11

During facilitated diffusion, which equation best describes the rate of solute movement across the membrane?

Accepted Answer

$$v = \frac{V_{max}[S]}{K_m + [S]}$$

Question 12

Which statement best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Their hydrophilic heads interact with water, while hydrophobic tails avoid water.

Question 13

Which process involves the plasma membrane pinching inward to take in large molecules?

Accepted Answer

Endocytosis

Question 14

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

Accepted Answer

Some proteins drift laterally within the bilayer, while others are anchored to the cytoskeleton or ECM.

Question 15

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have both hydrophilic heads and hydrophobic tails.

Question 16

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

Accepted Answer

Glucose entering a muscle cell via a GLUT transporter

Question 17

Which of the following membrane components is most variable among different cell types and individuals, and is crucial for cell-cell recognition?

Accepted Answer

Membrane carbohydrates

Question 18

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

Accepted Answer

Cholesterol decreases membrane fluidity at high temperatures and increases it at low temperatures.

Question 19

Which process is used by cells to secrete large molecules, such as hormones, into the extracellular space?

Accepted Answer

Exocytosis

Question 20

Which of the following best explains why integral proteins often contain alpha helices in their hydrophobic regions?

Accepted Answer

Alpha helices are formed by nonpolar amino acids, allowing the protein to stably embed in the hydrophobic core of the membrane.

Membrane Structure and Function Part 1

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