Question 1

Which of the following best explains why the hydrophobic core of the lipid bilayer acts as a permeability barrier to ions and polar molecules?

Accepted Answer

Ions and polar molecules must shed their hydration shells to enter the hydrophobic core, which is energetically unfavorable.

Question 2

A patient with a genetic disorder has red blood cells that are spherical rather than biconcave. Which membrane-associated protein is most likely defective?

Accepted Answer

Spectrin

Question 3

Which of the following changes would most increase the fluidity of a cell membrane at body temperature?

Accepted Answer

Increasing the proportion of cis-unsaturated fatty acids

Question 4

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

Accepted Answer

Cholesterol prevents the membrane from becoming too rigid by disrupting tight packing of phospholipid tails.

Question 5

Which of the following is a key difference between glycolipids and glycoproteins in the plasma membrane?

Accepted Answer

Glycolipids have carbohydrate chains attached to lipids, while glycoproteins have carbohydrate chains attached to proteins.

Question 6

A mutation in the gene encoding flippase would most likely disrupt which cellular process?

Accepted Answer

Maintenance of membrane phospholipid asymmetry

Question 7

Which of the following best explains why triacylglycerols do NOT form bilayers in water?

Accepted Answer

They are fully hydrophobic and lack a polar head group.

Question 8

Which of the following is a clinical consequence of phosphatidylserine (PS) externalization during apoptosis?

Accepted Answer

It signals macrophages to phagocytose the apoptotic cell without inflammation.

Question 9

Which of the following statements about lipid rafts is CORRECT?

Accepted Answer

Lipid rafts are enriched in cholesterol and sphingolipids, and cluster specific proteins for signaling.

Question 10

A cell is exposed to a drug that rigidifies its plasma membrane. Which of the following changes in membrane lipid composition would most likely explain this effect?

Accepted Answer

Increased proportion of long, saturated fatty acid chains

Question 11

Which of the following best describes the Fluid Mosaic Model of biological membranes?

Accepted Answer

Membranes are dynamic, with lateral movement of lipids and proteins, and rare flip-flop of phospholipids.

Question 12

Which of the following is a function of the glycocalyx on the external surface of eukaryotic cells?

Accepted Answer

Mediating cell-cell recognition and adhesion

Question 13

Which of the following best explains why most membrane phospholipids contain one saturated and one unsaturated fatty acid tail?

Accepted Answer

To provide a balance between membrane rigidity and fluidity

Question 14

Which of the following is TRUE regarding the sidedness (asymmetry) of biological membranes?

Accepted Answer

Glycolipids and glycoproteins are typically found on the extracellular side.

Question 15

A researcher is studying a membrane protein that spans the bilayer multiple times as α-helices. Which of the following is the most likely function of this protein?

Accepted Answer

Forming an ion channel or receptor

Question 16

Which of the following best describes the effect of cholesterol on membrane fluidity at body temperature?

Accepted Answer

Cholesterol decreases fluidity by restricting the motion of fatty acid tails.

Question 17

Which of the following is a consequence of disrupted lipid rafts in the context of insulin signaling?

Accepted Answer

Failure of insulin receptor, PI3K, and IRS-1 co-localization, leading to insulin resistance

Question 18

Which of the following best explains why peripheral membrane proteins are found only on the cytosolic face of the plasma membrane?

Accepted Answer

They bind to the charged head groups of inner-leaflet phospholipids such as phosphatidylserine.

Question 19

Which of the following is a real-world application of liposomes in medicine?

Accepted Answer

Delivering drugs to specific tissues via surface modifications

Biological Membranes: Structure, Composition, and Function

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