Question 1

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

Accepted Answer

Because the membrane is a dynamic structure with proteins embedded in or attached to a fluid bilayer of phospholipids.

Question 2

A red blood cell is placed in a solution and swells until it bursts. Which process is primarily responsible for this outcome?

Accepted Answer

Osmosis of water into the cell due to a hypotonic environment.

Question 3

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

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the membrane.

Question 4

Which molecule acts as a 'fluidity buffer' in animal cell membranes, helping to maintain membrane fluidity across temperature changes?

Accepted Answer

Cholesterol

Question 5

A cell needs to move glucose against its concentration gradient. Which process and membrane component are required?

Accepted Answer

Active transport using a carrier protein and ATP

Question 6

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

Accepted Answer

They have hydrophilic heads and hydrophobic tails.

Question 7

Which of the following is a function of membrane proteins that is critical for immune system recognition?

Accepted Answer

Cell-cell recognition

Question 8

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 with specific carbohydrate chains

Question 9

Which of the following statements about integral membrane proteins is correct?

Accepted Answer

They penetrate the hydrophobic core of the lipid bilayer.

Question 10

Which of the following best explains why ions such as $$ \mathrm{Na^+} $$ and $$ \mathrm{K^+} $$ cannot easily cross the plasma membrane without assistance?

Accepted Answer

They are repelled by the hydrophobic core of the membrane.

Question 11

A cell is placed in a hypertonic solution. What will most likely happen to the cell, and which process is responsible?

Accepted Answer

The cell will shrink as water leaves by osmosis.

Question 12

Which of the following best describes the role of cholesterol in the plasma membrane at high temperatures?

Accepted Answer

It decreases membrane fluidity by restraining phospholipid movement.

Question 13

Which of the following is an example of facilitated diffusion?

Accepted Answer

Glucose entering a cell through a specific carrier protein.

Question 14

Which of the following statements about peripheral membrane proteins is true?

Accepted Answer

They are loosely attached to the membrane surface, often to integral proteins.

Question 15

A scientist observes that a certain protein is anchored to the cytoskeleton inside the cell. What is the most likely function of this protein?

Accepted Answer

Maintaining cell shape and stabilizing membrane protein location

Question 16

Which of the following best describes the hydrophobic region of a transmembrane protein?

Accepted Answer

It is composed mainly of nonpolar amino acids arranged in alpha helices.

Question 17

Which process is responsible for the secretion of large molecules, such as hormones, from a cell?

Accepted Answer

Exocytosis

Question 18

A cell is observed to take in large particles by engulfing them with its plasma membrane, forming a vesicle. Which process is this?

Accepted Answer

Endocytosis

Question 19

Which of the following best explains why the plasma membrane is selectively permeable?

Accepted Answer

Its structure allows some substances to cross more easily than others.

Question 20

Which of the following is a real-life example of the importance of membrane carbohydrates in medicine?

Accepted Answer

Blood type compatibility in transfusions determined by glycoprotein carbohydrates.

Membrane Structure and Function: The Fluid Mosaic Model and Cellular Transport

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