Question 1

Which of the following best describes the structure of a biological membrane according to the fluid mosaic model?

Accepted Answer

A fluid phospholipid bilayer with a mosaic of proteins floating within or attached to the bilayer

Question 2

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

Accepted Answer

Phospholipid bilayer

Question 3

A researcher observes that a cell membrane becomes more rigid at lower temperatures. Which change in membrane composition would most likely increase membrane fluidity under these conditions?

Accepted Answer

Increasing the proportion of unsaturated fatty acids

Question 4

Which of the following statements about membrane proteins is correct?

Accepted Answer

Integral membrane proteins have hydrophobic regions that interact with the membrane interior

Question 5

What is the main function of glycoproteins in the plasma membrane?

Accepted Answer

To serve as recognition markers for cell-cell interactions

Question 6

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their cis double bonds create kinks that prevent tight packing of lipid molecules

Question 7

A mutation causes a cell to lack flippase enzymes. Which process would be most directly affected?

Accepted Answer

Transverse diffusion (flip-flop) of phospholipids between membrane leaflets

Question 8

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

Accepted Answer

Forming the permeability barrier of the membrane

Question 9

Which of the following statements about cholesterol in animal cell membranes is TRUE?

Accepted Answer

Cholesterol acts as a fluidity buffer, increasing fluidity at low temperatures and decreasing it at high temperatures

Question 10

A scientist isolates a membrane protein that is covalently attached to a fatty acid embedded in the bilayer. This protein is best classified as:

Accepted Answer

Lipid-anchored membrane protein

Question 11

Which of the following best describes the asymmetry of biological membranes?

Accepted Answer

The two leaflets of the bilayer have different lipid and protein compositions, contributing to functional differences

Question 12

Which experimental evidence was most critical in establishing the fluid mosaic model of membrane structure?

Accepted Answer

Observation of freeze-fracture electron microscopy showing proteins embedded within the bilayer

Question 13

A patient has a genetic disorder that reduces the number of glycolipids in their plasma membrane. Which of the following cellular processes is most likely to be impaired?

Accepted Answer

Cell recognition and immune response

Question 14

Which of the following changes would most likely decrease the melting temperature ($T_m$) of a membrane?

Accepted Answer

Increasing the proportion of unsaturated fatty acids

Question 15

Which of the following is a correct equation for the relationship between the number of double bonds in a fatty acid and the membrane's melting temperature ($T_m$)?

Accepted Answer

$T_m \propto \frac{1}{n_{	ext{double bonds}}}$

Question 16

Which of the following best explains why membrane proteins are difficult to study using traditional biochemical techniques?

Accepted Answer

They are often embedded in the hydrophobic core of the membrane, making them difficult to extract without disrupting their structure

Question 17

A cell is exposed to a toxin that specifically disrupts lipid rafts. Which process is most likely to be affected?

Accepted Answer

Cell signaling pathways involving G protein-coupled receptors

Question 18

Which of the following statements about the movement of phospholipids in the membrane is correct?

Accepted Answer

Lateral diffusion and rotation are common and rapid

Question 19

Which of the following is a real-world example of the importance of membrane asymmetry?

Accepted Answer

The exposure of phosphatidylserine on the outer leaflet of the plasma membrane during apoptosis, signaling phagocytic cells to engulf the dying cell

Membranes: Structure, Function, and Chemistry

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