Question 1

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

Accepted Answer

The cis double bonds in unsaturated fatty acids introduce kinks, preventing tight packing of lipid tails.

Question 2

Which of the following statements about cholesterol in biological membranes is CORRECT?

Accepted Answer

Cholesterol modulates membrane fluidity by disrupting the packing of fatty acid tails.

Question 3

A patient is diagnosed with a genetic disorder that impairs the function of flippases. Which of the following cellular processes would be most directly affected?

Accepted Answer

Transverse movement of phospholipids between membrane leaflets

Question 4

Which of the following best describes the amphipathic nature of membrane lipids?

Accepted Answer

They contain both a hydrophilic head group and a hydrophobic tail.

Question 5

Which of the following is a distinguishing feature of integral membrane proteins compared to peripheral membrane proteins?

Accepted Answer

They span the lipid bilayer and interact with the hydrophobic core.

Question 6

Which of the following best explains why water can slowly diffuse across the lipid bilayer despite being a polar molecule?

Accepted Answer

Water is small and uncharged, allowing limited passive diffusion.

Question 7

A researcher is studying a membrane protein that is easily removed by washing with a high salt solution. This protein is most likely:

Accepted Answer

A peripheral membrane protein

Question 8

Which of the following is TRUE regarding the sodium-potassium pump (Na⁺/K⁺-ATPase)?

Accepted Answer

It directly uses ATP hydrolysis to move ions against their concentration gradients.

Question 9

Which of the following best describes the function of glycolipids in the plasma membrane?

Accepted Answer

They are involved in cell-cell recognition and signaling.

Question 10

Which of the following statements about membrane rafts is CORRECT?

Accepted Answer

They contain clusters of glycosphingolipids and large transmembrane proteins.

Question 11

Which of the following best explains why the removal of the hydration shell is a high-energy barrier for passive diffusion of polar molecules across the membrane?

Accepted Answer

The hydrophobic core of the membrane repels polar molecules, requiring energy to desolvate them.

Question 12

Which of the following is a property of facilitated diffusion but NOT simple diffusion?

Accepted Answer

Requirement for a specific membrane protein transporter

Question 13

A mutation causes a membrane protein to have several charged amino acids in its transmembrane domain. What is the most likely consequence?

Accepted Answer

The protein will be less likely to span the hydrophobic core of the membrane.

Question 14

Which of the following best describes the role of van der Waals interactions in membrane structure?

Accepted Answer

They stabilize the interactions between hydrophobic fatty acid tails in the bilayer.

Question 15

Which of the following is TRUE regarding the movement of lipids in the membrane?

Accepted Answer

Lateral diffusion of lipids is rapid, while transverse diffusion is rare without enzymes.

Question 16

Which of the following best describes the function of the GLUT1 transporter?

Accepted Answer

It facilitates the passive transport of glucose down its concentration gradient.

Question 17

Which of the following is a key difference between primary and secondary active transport?

Accepted Answer

Primary active transport directly uses ATP hydrolysis, while secondary active transport uses ion gradients established by primary transport.

Question 18

Which of the following is a function of membrane proteins?

Accepted Answer

Acting as receptors, channels, enzymes, and anchors

Question 19

Which of the following best describes the composition of the outer leaflet of the plasma membrane?

Accepted Answer

It is enriched in glycolipids and sphingomyelin.

Question 20

Which of the following statements about the fluid mosaic model is CORRECT?

Accepted Answer

Membranes are dynamic structures with proteins and lipids capable of lateral movement.

Biological Membranes: Structure and Function – Study Notes

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