Question 1

Which of the following best describes the Fluid-Mosaic Model of membrane structure?

Accepted Answer

A dynamic structure with proteins and lipids able to move laterally within the bilayer, resembling a mosaic.

Question 2

Which of the following is a major function of biological membranes?

Accepted Answer

Facilitating selective transport of substances into and out of the cell.

Question 3

Based on Table 7-1, which of the following is the major conclusion regarding the biomolecule content of membranes?

Accepted Answer

The relative amounts of lipids, proteins, and carbohydrates vary depending on membrane type and function.

Question 4

Which structural feature distinguishes a phospholipid from a sterol?

Accepted Answer

Phospholipids contain a phosphate group and two fatty acid tails, while sterols have a four-ring core structure.

Question 5

Which type of lipid movement occurs most readily in biological membranes?

Accepted Answer

Lateral diffusion within the same leaflet.

Question 6

A cell membrane is found to be unusually rigid at room temperature. Which of the following is most likely to be true about its lipid composition?

Accepted Answer

It contains a high proportion of saturated fatty acids and long fatty acid chains.

Question 7

How does the presence of unsaturated fatty acids in membrane phospholipids affect membrane fluidity?

Accepted Answer

It increases membrane fluidity by introducing kinks that prevent tight packing.

Question 8

Which of the following best explains the effect of fatty acid chain length on membrane fluidity?

Accepted Answer

Shorter fatty acid chains increase membrane fluidity by reducing van der Waals interactions.

Question 9

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

Accepted Answer

They span the lipid bilayer and often contain hydrophobic regions that interact with the membrane interior.

Question 10

A hydropathy plot is used to:

Accepted Answer

Predict transmembrane regions of a protein based on hydrophobicity.

Question 11

Which of the following best describes a peripheral membrane protein?

Accepted Answer

It is loosely associated with the membrane surface, often through interactions with integral proteins or lipid head groups.

Question 12

Which of the following is a common feature of membrane carbohydrates?

Accepted Answer

They are covalently linked to membrane proteins or lipids.

Question 13

A mutation causes a membrane protein to lose its lipid anchor. Which of the following is the most likely consequence?

Accepted Answer

The protein will become a peripheral membrane protein and may dissociate from the membrane.

Question 14

A researcher observes that a certain membrane protein does not move laterally within the membrane. Which of the following is the most likely explanation?

Accepted Answer

The protein is attached to an internal cytoskeletal or external extracellular matrix anchor.

Question 15

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

Cholesterol modulates membrane fluidity by preventing tight packing of phospholipids at low temperatures and restricting movement at high temperatures.

Question 16

A patient with a genetic disorder has cell membranes that are excessively permeable to small ions. Which of the following changes in membrane composition could explain this observation?

Accepted Answer

Decreased cholesterol content in the membrane.

Question 17

Which of the following best describes the movement of membrane proteins?

Accepted Answer

They can move laterally within the membrane unless restricted by anchoring structures.

Question 18

A scientist is analyzing a membrane protein and finds a long stretch of hydrophobic amino acids in its primary sequence. What is the most likely function of this region?

Accepted Answer

It forms a transmembrane domain that spans the lipid bilayer.

Question 19

Which of the following scenarios best illustrates the concept of the 'mosaic' in the Fluid-Mosaic Model?

Accepted Answer

A membrane with a diverse array of proteins and lipids distributed unevenly within the bilayer.

Question 20

A cell is exposed to a drug that increases the proportion of unsaturated fatty acids in its membranes. Which of the following is the most likely effect?

Accepted Answer

The membrane will become more fluid and more permeable.

Chapter 7: Membranes – Structure, Function, and Chemistry

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